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<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>AltOS</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="book"><div class="titlepage"><div><div><h1 class="title"><a name="idm46302637457168"></a>AltOS</h1></div><div><h2 class="subtitle">Altos Metrum Operating System</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Keith</span> <span class="surname">Packard</span></h3></div></div><div><p class="copyright">Copyright © 2010 Keith Packard</p></div><div><div class="legalnotice"><a name="idm46302611036384"></a><p>
This document is released under the terms of the
<a class="ulink" href="http://creativecommons.org/licenses/by-sa/3.0/" target="_top">
Creative Commons ShareAlike 3.0
</a>
license.
</p></div></div><div><div class="revhistory"><table style="border-style:solid; width:100%;" summary="Revision History"><tr><th align="left" valign="top" colspan="2"><b>Revision History</b></th></tr><tr><td align="left">Revision 1.1</td><td align="left">05 November 2012</td></tr><tr><td align="left" colspan="2">Portable version</td></tr><tr><td align="left">Revision 0.1</td><td align="left">22 November 2010</td></tr><tr><td align="left" colspan="2">Initial content</td></tr></table></div></div></div><hr></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="chapter"><a href="#idm46302610177888">1. Overview</a></span></dt><dt><span class="chapter"><a href="#idm46302610940496">2. AltOS Porting Layer</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302610938992">1. Low-level CPU operations</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302610937760">1.1. ao_arch_block_interrupts/ao_arch_release_interrupts</a></span></dt><dt><span class="section"><a href="#idm46302610935712">1.2. ao_arch_save_regs, ao_arch_save_stack,
ao_arch_restore_stack</a></span></dt><dt><span class="section"><a href="#idm46302610933424">1.3. ao_arch_wait_interupt</a></span></dt></dl></dd><dt><span class="section"><a href="#idm46302610930880">2. GPIO operations</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302610929712">2.1. GPIO setup</a></span></dt><dt><span class="section"><a href="#idm46302611109712">2.2. Reading and writing GPIO pins</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#idm46302611104464">3. Programming the 8051 with SDCC</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302611102368">1. 8051 memory spaces</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302611100432">1.1. __data</a></span></dt><dt><span class="section"><a href="#idm46302611098256">1.2. __idata</a></span></dt><dt><span class="section"><a href="#idm46302611096816">1.3. __xdata</a></span></dt><dt><span class="section"><a href="#idm46302611095408">1.4. __pdata</a></span></dt><dt><span class="section"><a href="#idm46302611093904">1.5. __code</a></span></dt><dt><span class="section"><a href="#idm46302611092464">1.6. __bit</a></span></dt><dt><span class="section"><a href="#idm46302611090960">1.7. __sfr, __sfr16, __sfr32, __sbit</a></span></dt></dl></dd><dt><span class="section"><a href="#idm46302611089424">2. Function calls on the 8051</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302611087952">2.1. __reentrant functions</a></span></dt><dt><span class="section"><a href="#idm46302611085760">2.2. Non __reentrant functions</a></span></dt><dt><span class="section"><a href="#idm46302611083616">2.3. __interrupt functions</a></span></dt><dt><span class="section"><a href="#idm46302611082048">2.4. __critical functions and statements</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#idm46302611079984">4. Task functions</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302611078928">1. ao_add_task</a></span></dt><dt><span class="section"><a href="#idm46302611076672">2. ao_exit</a></span></dt><dt><span class="section"><a href="#idm46302605188160">3. ao_sleep</a></span></dt><dt><span class="section"><a href="#idm46302605184560">4. ao_wakeup</a></span></dt><dt><span class="section"><a href="#idm46302605181568">5. ao_alarm</a></span></dt><dt><span class="section"><a href="#idm46302605178288">6. ao_start_scheduler</a></span></dt><dt><span class="section"><a href="#idm46302605176320">7. ao_clock_init</a></span></dt></dl></dd><dt><span class="chapter"><a href="#idm46302605174224">5. Timer Functions</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302605172720">1. ao_time</a></span></dt><dt><span class="section"><a href="#idm46302605170688">2. ao_delay</a></span></dt><dt><span class="section"><a href="#idm46302605168768">3. ao_timer_set_adc_interval</a></span></dt><dt><span class="section"><a href="#idm46302605166640">4. ao_timer_init</a></span></dt></dl></dd><dt><span class="chapter"><a href="#idm46302605164448">6. AltOS Mutexes</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302605162576">1. ao_mutex_get</a></span></dt><dt><span class="section"><a href="#idm46302605160736">2. ao_mutex_put</a></span></dt></dl></dd><dt><span class="chapter"><a href="#idm46302605158672">7. DMA engine</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302605155232">1. CC1111 DMA Engine</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302605154560">1.1. ao_dma_alloc</a></span></dt><dt><span class="section"><a href="#idm46302605152384">1.2. ao_dma_set_transfer</a></span></dt><dt><span class="section"><a href="#idm46302605150112">1.3. ao_dma_start</a></span></dt><dt><span class="section"><a href="#idm46302605148096">1.4. ao_dma_trigger</a></span></dt><dt><span class="section"><a href="#idm46302605146176">1.5. ao_dma_abort</a></span></dt></dl></dd><dt><span class="section"><a href="#idm46302605144032">2. STM32L DMA Engine</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302605143360">2.1. ao_dma_alloc</a></span></dt><dt><span class="section"><a href="#idm46302605141360">2.2. ao_dma_set_transfer</a></span></dt><dt><span class="section"><a href="#idm46302605139104">2.3. ao_dma_set_isr</a></span></dt><dt><span class="section"><a href="#idm46302605136944">2.4. ao_dma_start</a></span></dt><dt><span class="section"><a href="#idm46302605134640">2.5. ao_dma_done_transfer</a></span></dt><dt><span class="section"><a href="#idm46302605132656">2.6. ao_dma_abort</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#idm46302605130384">8. Stdio interface</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302605128880">1. putchar</a></span></dt><dt><span class="section"><a href="#idm46302605126912">2. getchar</a></span></dt><dt><span class="section"><a href="#idm46302605124816">3. flush</a></span></dt><dt><span class="section"><a href="#idm46302605122784">4. ao_add_stdio</a></span></dt></dl></dd><dt><span class="chapter"><a href="#idm46302605118752">9. Command line interface</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302605117344">1. ao_cmd_register</a></span></dt><dt><span class="section"><a href="#idm46302605108608">2. ao_cmd_lex</a></span></dt><dt><span class="section"><a href="#idm46302605106528">3. ao_cmd_put16</a></span></dt><dt><span class="section"><a href="#idm46302605104688">4. ao_cmd_put8</a></span></dt><dt><span class="section"><a href="#idm46302605102800">5. ao_cmd_white</a></span></dt><dt><span class="section"><a href="#idm46302605100736">6. ao_cmd_hex</a></span></dt><dt><span class="section"><a href="#idm46302605098688">7. ao_cmd_decimal</a></span></dt><dt><span class="section"><a href="#idm46302605096592">8. ao_match_word</a></span></dt><dt><span class="section"><a href="#idm46302605094512">9. ao_cmd_init</a></span></dt></dl></dd><dt><span class="chapter"><a href="#idm46302605092288">10. USB target device</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302605090064">1. ao_usb_flush</a></span></dt><dt><span class="section"><a href="#idm46302605087920">2. ao_usb_putchar</a></span></dt><dt><span class="section"><a href="#idm46302605085744">3. ao_usb_pollchar</a></span></dt><dt><span class="section"><a href="#idm46302605083600">4. ao_usb_getchar</a></span></dt><dt><span class="section"><a href="#idm46302605081584">5. ao_usb_disable</a></span></dt><dt><span class="section"><a href="#idm46302605078752">6. ao_usb_enable</a></span></dt><dt><span class="section"><a href="#idm46302605076640">7. ao_usb_init</a></span></dt></dl></dd><dt><span class="chapter"><a href="#idm46302605074416">11. Serial peripherals</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302605072400">1. ao_serial_getchar</a></span></dt><dt><span class="section"><a href="#idm46302605070368">2. ao_serial_putchar</a></span></dt><dt><span class="section"><a href="#idm46302605068400">3. ao_serial_drain</a></span></dt><dt><span class="section"><a href="#idm46302605066400">4. ao_serial_set_speed</a></span></dt><dt><span class="section"><a href="#idm46302605064368">5. ao_serial_init</a></span></dt></dl></dd><dt><span class="chapter"><a href="#idm46302605062176">12. CC1111 Radio peripheral</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302605061504">1. Radio Introduction</a></span></dt><dt><span class="section"><a href="#idm46302605054896">2. ao_radio_set_telemetry</a></span></dt><dt><span class="section"><a href="#idm46302605052800">3. ao_radio_set_packet</a></span></dt><dt><span class="section"><a href="#idm46302605050704">4. ao_radio_set_rdf</a></span></dt><dt><span class="section"><a href="#idm46302605048576">5. ao_radio_idle</a></span></dt><dt><span class="section"><a href="#idm46302605046640">6. ao_radio_get</a></span></dt><dt><span class="section"><a href="#idm46302605044720">7. ao_radio_put</a></span></dt><dt><span class="section"><a href="#idm46302605042944">8. ao_radio_abort</a></span></dt><dt><span class="section"><a href="#idm46302605040992">9. Radio Telemetry</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302605039728">9.1. ao_radio_send</a></span></dt><dt><span class="section"><a href="#idm46302605037568">9.2. ao_radio_recv</a></span></dt></dl></dd><dt><span class="section"><a href="#idm46302605035168">10. Radio Direction Finding</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302605034048">10.1. ao_radio_rdf</a></span></dt></dl></dd><dt><span class="section"><a href="#idm46302605032016">11. Radio Packet Mode</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302605030736">11.1. ao_packet_putchar</a></span></dt><dt><span class="section"><a href="#idm46302605028624">11.2. ao_packet_pollchar</a></span></dt><dt><span class="section"><a href="#idm46302605026656">11.3. ao_packet_slave_start</a></span></dt><dt><span class="section"><a href="#idm46302605024768">11.4. ao_packet_slave_stop</a></span></dt><dt><span class="section"><a href="#idm46302605022912">11.5. ao_packet_slave_init</a></span></dt><dt><span class="section"><a href="#idm46302605020944">11.6. ao_packet_master_init</a></span></dt></dl></dd></dl></dd></dl></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="idm46302610177888"></a>Chapter 1. Overview</h1></div></div></div><p>
AltOS is a operating system built for a variety of
microcontrollers used in Altus Metrum devices. It has a simple
porting layer for each CPU while providing a convenient
operating enviroment for the developer. AltOS currently
supports three different CPUs:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
STM32L series from ST Microelectronics. This ARM Cortex-M3
based microcontroller offers low power consumption and a
wide variety of built-in peripherals. Altus Metrum uses
this in the TeleMega, MegaDongle and TeleLCO projects.
</p></li><li class="listitem"><p>
CC1111 from Texas Instruments. This device includes a
fabulous 10mW digital RF transceiver along with an
8051-compatible processor core and a range of
peripherals. This is used in the TeleMetrum, TeleMini,
TeleDongle and TeleFire projects which share the need for
a small microcontroller and an RF interface.
</p></li><li class="listitem"><p>
ATmega32U4 from Atmel. This 8-bit AVR microcontroller is
one of the many used to create Arduino boards. The 32U4
includes a USB interface, making it easy to connect to
other computers. Altus Metrum used this in prototypes of
the TeleScience and TelePyro boards; those have been
switched to the STM32L which is more capable and cheaper.
</p></li></ul></div><p>
Among the features of AltOS are:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Multi-tasking. While microcontrollers often don't
provide separate address spaces, it's often easier to write
code that operates in separate threads instead of tying
everything into one giant event loop.
</p></li><li class="listitem"><p>Non-preemptive. This increases latency for thread
switching but reduces the number of places where context
switching can occur. It also simplifies the operating system
design somewhat. Nothing in the target system (rocket flight
control) has tight timing requirements, and so this seems like
a reasonable compromise.
</p></li><li class="listitem"><p>Sleep/wakeup scheduling. Taken directly from ancient
Unix designs, these two provide the fundemental scheduling
primitive within AltOS.
</p></li><li class="listitem"><p>Mutexes. As a locking primitive, mutexes are easier to
use than semaphores, at least in my experience.
</p></li><li class="listitem"><p>Timers. Tasks can set an alarm which will abort any
pending sleep, allowing operations to time-out instead of
blocking forever.
</p></li></ul></div><p>
</p><p>
The device drivers and other subsystems in AltOS are
conventionally enabled by invoking their _init() function from
the 'main' function before that calls
ao_start_scheduler(). These functions initialize the pin
assignments, add various commands to the command processor and
may add tasks to the scheduler to handle the device. A typical
main program, thus, looks like:
</p><pre class="programlisting">
void
main(void)
{
ao_clock_init();
/* Turn on the LED until the system is stable */
ao_led_init(LEDS_AVAILABLE);
ao_led_on(AO_LED_RED);
ao_timer_init();
ao_cmd_init();
ao_usb_init();
ao_monitor_init(AO_LED_GREEN, TRUE);
ao_rssi_init(AO_LED_RED);
ao_radio_init();
ao_packet_slave_init();
ao_packet_master_init();
#if HAS_DBG
ao_dbg_init();
#endif
ao_config_init();
ao_start_scheduler();
}
</pre><p>
As you can see, a long sequence of subsystems are initialized
and then the scheduler is started.
</p></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="idm46302610940496"></a>Chapter 2. AltOS Porting Layer</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#idm46302610938992">1. Low-level CPU operations</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302610937760">1.1. ao_arch_block_interrupts/ao_arch_release_interrupts</a></span></dt><dt><span class="section"><a href="#idm46302610935712">1.2. ao_arch_save_regs, ao_arch_save_stack,
ao_arch_restore_stack</a></span></dt><dt><span class="section"><a href="#idm46302610933424">1.3. ao_arch_wait_interupt</a></span></dt></dl></dd><dt><span class="section"><a href="#idm46302610930880">2. GPIO operations</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302610929712">2.1. GPIO setup</a></span></dt><dt><span class="section"><a href="#idm46302611109712">2.2. Reading and writing GPIO pins</a></span></dt></dl></dd></dl></div><p>
AltOS provides a CPU-independent interface to various common
microcontroller subsystems, including GPIO pins, interrupts,
SPI, I2C, USB and asynchronous serial interfaces. By making
these CPU-independent, device drivers, generic OS and
application code can all be written that work on any supported
CPU. Many of the architecture abstraction interfaces are
prefixed with ao_arch.
</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302610938992"></a>1. Low-level CPU operations</h2></div></div></div><p>
These primitive operations provide the abstraction needed to
run the multi-tasking framework while providing reliable
interrupt delivery.
</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302610937760"></a>1.1. ao_arch_block_interrupts/ao_arch_release_interrupts</h3></div></div></div><pre class="programlisting">
static inline void
ao_arch_block_interrupts(void);
static inline void
ao_arch_release_interrupts(void);
</pre><p>
These disable/enable interrupt delivery, they may not
discard any interrupts. Use these for sections of code that
must be atomic with respect to any code run from an
interrupt handler.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302610935712"></a>1.2. ao_arch_save_regs, ao_arch_save_stack,
ao_arch_restore_stack</h3></div></div></div><pre class="programlisting">
static inline void
ao_arch_save_regs(void);
static inline void
ao_arch_save_stack(void);
static inline void
ao_arch_restore_stack(void);
</pre><p>
These provide all of the support needed to switch between
tasks.. ao_arch_save_regs must save all CPU registers to the
current stack, including the interrupt enable
state. ao_arch_save_stack records the current stack location
in the current ao_task structure. ao_arch_restore_stack
switches back to the saved stack, restores all registers and
branches to the saved return address.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302610933424"></a>1.3. ao_arch_wait_interupt</h3></div></div></div><pre class="programlisting">
#define ao_arch_wait_interrupt()
</pre><p>
This stops the CPU, leaving clocks and interrupts
enabled. When an interrupt is received, this must wake up
and handle the interrupt. ao_arch_wait_interrupt is entered
with interrupts disabled to ensure that there is no gap
between determining that no task wants to run and idling the
CPU. It must sleep the CPU, process interrupts and then
disable interrupts again. If the CPU doesn't have any
reduced power mode, this must at the least allow pending
interrupts to be processed.
</p></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302610930880"></a>2. GPIO operations</h2></div></div></div><p>
These functions provide an abstract interface to configure and
manipulate GPIO pins.
</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302610929712"></a>2.1. GPIO setup</h3></div></div></div><p>
These macros may be invoked at system initialization time to
configure pins as needed for system operation. One tricky
aspect is that some chips provide direct access to specific
GPIO pins while others only provide access to a whole
register full of pins. To support this, the GPIO macros
provide both port+bit and pin arguments. Simply define the
arguments needed for the target platform and leave the
others undefined.
</p><div class="section"><div class="titlepage"><div><div><h4 class="title"><a name="idm46302610927744"></a>2.1.1. ao_enable_output</h4></div></div></div><pre class="programlisting">
#define ao_enable_output(port, bit, pin, value)
</pre><p>
Set the specified port+bit (also called 'pin') for output,
initializing to the specified value. The macro must avoid
driving the pin with the opposite value if at all
possible.
</p></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a name="idm46302611115152"></a>2.1.2. ao_enable_input</h4></div></div></div><pre class="programlisting">
#define ao_enable_input(port, bit, mode)
</pre><p>
Sets the specified port/bit to be an input pin. 'mode' is
a combination of one or more of the following. Note that
some platforms may not support the desired mode. In that
case, the value will not be defined so that the program
will fail to compile.
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
AO_EXTI_MODE_PULL_UP. Apply a pull-up to the pin; a
disconnected pin will read as 1.
</p></li><li class="listitem"><p>
AO_EXTI_MODE_PULL_DOWN. Apply a pull-down to the pin;
a disconnected pin will read as 0.
</p></li><li class="listitem"><p>
0. Don't apply either a pull-up or pull-down. A
disconnected pin will read an undetermined value.
</p></li></ul></div><p>
</p></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302611109712"></a>2.2. Reading and writing GPIO pins</h3></div></div></div><p>
These macros read and write individual GPIO pins.
</p><div class="section"><div class="titlepage"><div><div><h4 class="title"><a name="idm46302611108640"></a>2.2.1. ao_gpio_set</h4></div></div></div><pre class="programlisting">
#define ao_gpio_set(port, bit, pin, value)
</pre><p>
Sets the specified port/bit or pin to the indicated value
</p></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a name="idm46302611106800"></a>2.2.2. ao_gpio_get</h4></div></div></div><pre class="programlisting">
#define ao_gpio_get(port, bit, pin)
</pre><p>
Returns either 1 or 0 depending on whether the input to
the pin is high or low.
</p></div></div></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="idm46302611104464"></a>Chapter 3. Programming the 8051 with SDCC</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#idm46302611102368">1. 8051 memory spaces</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302611100432">1.1. __data</a></span></dt><dt><span class="section"><a href="#idm46302611098256">1.2. __idata</a></span></dt><dt><span class="section"><a href="#idm46302611096816">1.3. __xdata</a></span></dt><dt><span class="section"><a href="#idm46302611095408">1.4. __pdata</a></span></dt><dt><span class="section"><a href="#idm46302611093904">1.5. __code</a></span></dt><dt><span class="section"><a href="#idm46302611092464">1.6. __bit</a></span></dt><dt><span class="section"><a href="#idm46302611090960">1.7. __sfr, __sfr16, __sfr32, __sbit</a></span></dt></dl></dd><dt><span class="section"><a href="#idm46302611089424">2. Function calls on the 8051</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302611087952">2.1. __reentrant functions</a></span></dt><dt><span class="section"><a href="#idm46302611085760">2.2. Non __reentrant functions</a></span></dt><dt><span class="section"><a href="#idm46302611083616">2.3. __interrupt functions</a></span></dt><dt><span class="section"><a href="#idm46302611082048">2.4. __critical functions and statements</a></span></dt></dl></dd></dl></div><p>
The 8051 is a primitive 8-bit processor, designed in the mists
of time in as few transistors as possible. The architecture is
highly irregular and includes several separate memory
spaces. Furthermore, accessing stack variables is slow, and the
stack itself is of limited size. While SDCC papers over the
instruction set, it is not completely able to hide the memory
architecture from the application designer.
</p><p>
When built on other architectures, the various SDCC-specific
symbols are #defined as empty strings so they don't affect the compiler.
</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302611102368"></a>1. 8051 memory spaces</h2></div></div></div><p>
The __data/__xdata/__code memory spaces below were completely
separate in the original 8051 design. In the cc1111, this
isn't true—they all live in a single unified 64kB address
space, and so it's possible to convert any address into a
unique 16-bit address. SDCC doesn't know this, and so a
'global' address to SDCC consumes 3 bytes of memory, 1 byte as
a tag indicating the memory space and 2 bytes of offset within
that space. AltOS avoids these 3-byte addresses as much as
possible; using them involves a function call per byte
access. The result is that nearly every variable declaration
is decorated with a memory space identifier which clutters the
code but makes the resulting code far smaller and more
efficient.
</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302611100432"></a>1.1. __data</h3></div></div></div><p>
The 8051 can directly address these 128 bytes of
memory. This makes them precious so they should be
reserved for frequently addressed values. Oh, just to
confuse things further, the 8 general registers in the
CPU are actually stored in this memory space. There are
magic instructions to 'bank switch' among 4 banks of
these registers located at 0x00 - 0x1F. AltOS uses only
the first bank at 0x00 - 0x07, leaving the other 24
bytes available for other data.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302611098256"></a>1.2. __idata</h3></div></div></div><p>
There are an additional 128 bytes of internal memory
that share the same address space as __data but which
cannot be directly addressed. The stack normally
occupies this space and so AltOS doesn't place any
static storage here.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302611096816"></a>1.3. __xdata</h3></div></div></div><p>
This is additional general memory accessed through a
single 16-bit address register. The CC1111F32 has 32kB
of memory available here. Most program data should live
in this memory space.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302611095408"></a>1.4. __pdata</h3></div></div></div><p>
This is an alias for the first 256 bytes of __xdata
memory, but uses a shorter addressing mode with
single global 8-bit value for the high 8 bits of the
address and any of several 8-bit registers for the low 8
bits. AltOS uses a few bits of this memory, it should
probably use more.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302611093904"></a>1.5. __code</h3></div></div></div><p>
All executable code must live in this address space, but
you can stick read-only data here too. It is addressed
using the 16-bit address register and special 'code'
access opcodes. Anything read-only should live in this space.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302611092464"></a>1.6. __bit</h3></div></div></div><p>
The 8051 has 128 bits of bit-addressible memory that
lives in the __data segment from 0x20 through
0x2f. Special instructions access these bits
in a single atomic operation. This isn't so much a
separate address space as a special addressing mode for
a few bytes in the __data segment.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302611090960"></a>1.7. __sfr, __sfr16, __sfr32, __sbit</h3></div></div></div><p>
Access to physical registers in the device use this mode
which declares the variable name, its type and the
address it lives at. No memory is allocated for these
variables.
</p></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302611089424"></a>2. Function calls on the 8051</h2></div></div></div><p>
Because stack addressing is expensive, and stack space
limited, the default function call declaration in SDCC
allocates all parameters and local variables in static global
memory. Just like fortran. This makes these functions
non-reentrant, and also consume space for parameters and
locals even when they are not running. The benefit is smaller
code and faster execution.
</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302611087952"></a>2.1. __reentrant functions</h3></div></div></div><p>
All functions which are re-entrant, either due to recursion
or due to a potential context switch while executing, should
be marked as __reentrant so that their parameters and local
variables get allocated on the stack. This ensures that
these values are not overwritten by another invocation of
the function.
</p><p>
Functions which use significant amounts of space for
arguments and/or local variables and which are not often
invoked can also be marked as __reentrant. The resulting
code will be larger, but the savings in memory are
frequently worthwhile.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302611085760"></a>2.2. Non __reentrant functions</h3></div></div></div><p>
All parameters and locals in non-reentrant functions can
have data space decoration so that they are allocated in
__xdata, __pdata or __data space as desired. This can avoid
consuming __data space for infrequently used variables in
frequently used functions.
</p><p>
All library functions called by SDCC, including functions
for multiplying and dividing large data types, are
non-reentrant. Because of this, interrupt handlers must not
invoke any library functions, including the multiply and
divide code.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302611083616"></a>2.3. __interrupt functions</h3></div></div></div><p>
Interrupt functions are declared with with an __interrupt
decoration that includes the interrupt number. SDCC saves
and restores all of the registers in these functions and
uses the 'reti' instruction at the end so that they operate
as stand-alone interrupt handlers. Interrupt functions may
call the ao_wakeup function to wake AltOS tasks.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302611082048"></a>2.4. __critical functions and statements</h3></div></div></div><p>
SDCC has built-in support for suspending interrupts during
critical code. Functions marked as __critical will have
interrupts suspended for the whole period of
execution. Individual statements may also be marked as
__critical which blocks interrupts during the execution of
that statement. Keeping critical sections as short as
possible is key to ensuring that interrupts are handled as
quickly as possible. AltOS doesn't use this form in shared
code as other compilers wouldn't know what to do. Use
ao_arch_block_interrupts and ao_arch_release_interrupts instead.
</p></div></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="idm46302611079984"></a>Chapter 4. Task functions</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#idm46302611078928">1. ao_add_task</a></span></dt><dt><span class="section"><a href="#idm46302611076672">2. ao_exit</a></span></dt><dt><span class="section"><a href="#idm46302605188160">3. ao_sleep</a></span></dt><dt><span class="section"><a href="#idm46302605184560">4. ao_wakeup</a></span></dt><dt><span class="section"><a href="#idm46302605181568">5. ao_alarm</a></span></dt><dt><span class="section"><a href="#idm46302605178288">6. ao_start_scheduler</a></span></dt><dt><span class="section"><a href="#idm46302605176320">7. ao_clock_init</a></span></dt></dl></div><p>
This chapter documents how to create, destroy and schedule AltOS tasks.
</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302611078928"></a>1. ao_add_task</h2></div></div></div><pre class="programlisting">
void
ao_add_task(__xdata struct ao_task * task,
void (*start)(void),
__code char *name);
</pre><p>
This initializes the statically allocated task structure,
assigns a name to it (not used for anything but the task
display), and the start address. It does not switch to the
new task. 'start' must not ever return; there is no place
to return to.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302611076672"></a>2. ao_exit</h2></div></div></div><pre class="programlisting">
void
ao_exit(void)
</pre><p>
This terminates the current task.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605188160"></a>3. ao_sleep</h2></div></div></div><pre class="programlisting">
void
ao_sleep(__xdata void *wchan)
</pre><p>
This suspends the current task until 'wchan' is signaled
by ao_wakeup, or until the timeout, set by ao_alarm,
fires. If 'wchan' is signaled, ao_sleep returns 0, otherwise
it returns 1. This is the only way to switch to another task.
</p><p>
Because ao_wakeup wakes every task waiting on a particular
location, ao_sleep should be used in a loop that first checks
the desired condition, blocks in ao_sleep and then rechecks
until the condition is satisfied. If the location may be
signaled from an interrupt handler, the code will need to
block interrupts around the block of code. Here's a complete
example:
</p><pre class="programlisting">
ao_arch_block_interrupts();
while (!ao_radio_done)
ao_sleep(&ao_radio_done);
ao_arch_release_interrupts();
</pre><p>
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605184560"></a>4. ao_wakeup</h2></div></div></div><pre class="programlisting">
void
ao_wakeup(__xdata void *wchan)
</pre><p>
Wake all tasks blocked on 'wchan'. This makes them
available to be run again, but does not actually switch
to another task. Here's an example of using this:
</p><pre class="programlisting">
if (RFIF & RFIF_IM_DONE) {
ao_radio_done = 1;
ao_wakeup(&ao_radio_done);
RFIF &= ~RFIF_IM_DONE;
}
</pre><p>
Note that this need not block interrupts as the ao_sleep block
can only be run from normal mode, and so this sequence can
never be interrupted with execution of the other sequence.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605181568"></a>5. ao_alarm</h2></div></div></div><pre class="programlisting">
void
ao_alarm(uint16_t delay);
void
ao_clear_alarm(void);
</pre><p>
Schedules an alarm to fire in at least 'delay' ticks. If the
task is asleep when the alarm fires, it will wakeup and
ao_sleep will return 1. ao_clear_alarm resets any pending
alarm so that it doesn't fire at some arbitrary point in the
future.
</p><pre class="programlisting">
ao_alarm(ao_packet_master_delay);
ao_arch_block_interrupts();
while (!ao_radio_dma_done)
if (ao_sleep(&ao_radio_dma_done) != 0)
ao_radio_abort();
ao_arch_release_interrupts();
ao_clear_alarm();
</pre><p>
In this example, a timeout is set before waiting for
incoming radio data. If no data is received before the
timeout fires, ao_sleep will return 1 and then this code
will abort the radio receive operation.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605178288"></a>6. ao_start_scheduler</h2></div></div></div><pre class="programlisting">
void
ao_start_scheduler(void);
</pre><p>
This is called from 'main' when the system is all
initialized and ready to run. It will not return.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605176320"></a>7. ao_clock_init</h2></div></div></div><pre class="programlisting">
void
ao_clock_init(void);
</pre><p>
This initializes the main CPU clock and switches to it.
</p></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="idm46302605174224"></a>Chapter 5. Timer Functions</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#idm46302605172720">1. ao_time</a></span></dt><dt><span class="section"><a href="#idm46302605170688">2. ao_delay</a></span></dt><dt><span class="section"><a href="#idm46302605168768">3. ao_timer_set_adc_interval</a></span></dt><dt><span class="section"><a href="#idm46302605166640">4. ao_timer_init</a></span></dt></dl></div><p>
AltOS sets up one of the CPU timers to run at 100Hz and
exposes this tick as the fundemental unit of time. At each
interrupt, AltOS increments the counter, and schedules any tasks
waiting for that time to pass, then fires off the sensors to
collect current data readings. Doing this from the ISR ensures
that the values are sampled at a regular rate, independent
of any scheduling jitter.
</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605172720"></a>1. ao_time</h2></div></div></div><pre class="programlisting">
uint16_t
ao_time(void)
</pre><p>
Returns the current system tick count. Note that this is
only a 16 bit value, and so it wraps every 655.36 seconds.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605170688"></a>2. ao_delay</h2></div></div></div><pre class="programlisting">
void
ao_delay(uint16_t ticks);
</pre><p>
Suspend the current task for at least 'ticks' clock units.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605168768"></a>3. ao_timer_set_adc_interval</h2></div></div></div><pre class="programlisting">
void
ao_timer_set_adc_interval(uint8_t interval);
</pre><p>
This sets the number of ticks between ADC samples. If set
to 0, no ADC samples are generated. AltOS uses this to
slow down the ADC sampling rate to save power.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605166640"></a>4. ao_timer_init</h2></div></div></div><pre class="programlisting">
void
ao_timer_init(void)
</pre><p>
This turns on the 100Hz tick. It is required for any of the
time-based functions to work. It should be called by 'main'
before ao_start_scheduler.
</p></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="idm46302605164448"></a>Chapter 6. AltOS Mutexes</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#idm46302605162576">1. ao_mutex_get</a></span></dt><dt><span class="section"><a href="#idm46302605160736">2. ao_mutex_put</a></span></dt></dl></div><p>
AltOS provides mutexes as a basic synchronization primitive. Each
mutexes is simply a byte of memory which holds 0 when the mutex
is free or the task id of the owning task when the mutex is
owned. Mutex calls are checked—attempting to acquire a mutex
already held by the current task or releasing a mutex not held
by the current task will both cause a panic.
</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605162576"></a>1. ao_mutex_get</h2></div></div></div><pre class="programlisting">
void
ao_mutex_get(__xdata uint8_t *mutex);
</pre><p>
Acquires the specified mutex, blocking if the mutex is
owned by another task.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605160736"></a>2. ao_mutex_put</h2></div></div></div><pre class="programlisting">
void
ao_mutex_put(__xdata uint8_t *mutex);
</pre><p>
Releases the specified mutex, waking up all tasks waiting
for it.
</p></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="idm46302605158672"></a>Chapter 7. DMA engine</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#idm46302605155232">1. CC1111 DMA Engine</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302605154560">1.1. ao_dma_alloc</a></span></dt><dt><span class="section"><a href="#idm46302605152384">1.2. ao_dma_set_transfer</a></span></dt><dt><span class="section"><a href="#idm46302605150112">1.3. ao_dma_start</a></span></dt><dt><span class="section"><a href="#idm46302605148096">1.4. ao_dma_trigger</a></span></dt><dt><span class="section"><a href="#idm46302605146176">1.5. ao_dma_abort</a></span></dt></dl></dd><dt><span class="section"><a href="#idm46302605144032">2. STM32L DMA Engine</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302605143360">2.1. ao_dma_alloc</a></span></dt><dt><span class="section"><a href="#idm46302605141360">2.2. ao_dma_set_transfer</a></span></dt><dt><span class="section"><a href="#idm46302605139104">2.3. ao_dma_set_isr</a></span></dt><dt><span class="section"><a href="#idm46302605136944">2.4. ao_dma_start</a></span></dt><dt><span class="section"><a href="#idm46302605134640">2.5. ao_dma_done_transfer</a></span></dt><dt><span class="section"><a href="#idm46302605132656">2.6. ao_dma_abort</a></span></dt></dl></dd></dl></div><p>
The CC1111 and STM32L both contain a useful bit of extra
hardware in the form of a number of programmable DMA
engines. They can be configured to copy data in memory, or
between memory and devices (or even between two devices). AltOS
exposes a general interface to this hardware and uses it to
handle both internal and external devices.
</p><p>
Because the CC1111 and STM32L DMA engines are different, the
interface to them is also different. As the DMA engines are
currently used to implement platform-specific drivers, this
isn't yet a problem.
</p><p>
Code using a DMA engine should allocate one at startup
time. There is no provision to free them, and if you run out,
AltOS will simply panic.
</p><p>
During operation, the DMA engine is initialized with the
transfer parameters. Then it is started, at which point it
awaits a suitable event to start copying data. When copying data
from hardware to memory, that trigger event is supplied by the
hardware device. When copying data from memory to hardware, the
transfer is usually initiated by software.
</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605155232"></a>1. CC1111 DMA Engine</h2></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605154560"></a>1.1. ao_dma_alloc</h3></div></div></div><pre class="programlisting">
uint8_t
ao_dma_alloc(__xdata uint8_t *done)
</pre><p>
Allocate a DMA engine, returning the identifier. 'done' is
cleared when the DMA is started, and then receives the
AO_DMA_DONE bit on a successful transfer or the
AO_DMA_ABORTED bit if ao_dma_abort was called. Note that it
is possible to get both bits if the transfer was aborted
after it had finished.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605152384"></a>1.2. ao_dma_set_transfer</h3></div></div></div><pre class="programlisting">
void
ao_dma_set_transfer(uint8_t id,
void __xdata *srcaddr,
void __xdata *dstaddr,
uint16_t count,
uint8_t cfg0,
uint8_t cfg1)
</pre><p>
Initializes the specified dma engine to copy data
from 'srcaddr' to 'dstaddr' for 'count' units. cfg0 and
cfg1 are values directly out of the CC1111 documentation
and tell the DMA engine what the transfer unit size,
direction and step are.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605150112"></a>1.3. ao_dma_start</h3></div></div></div><pre class="programlisting">
void
ao_dma_start(uint8_t id);
</pre><p>
Arm the specified DMA engine and await a signal from
either hardware or software to start transferring data.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605148096"></a>1.4. ao_dma_trigger</h3></div></div></div><pre class="programlisting">
void
ao_dma_trigger(uint8_t id)
</pre><p>
Trigger the specified DMA engine to start copying data.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605146176"></a>1.5. ao_dma_abort</h3></div></div></div><pre class="programlisting">
void
ao_dma_abort(uint8_t id)
</pre><p>
Terminate any in-progress DMA transaction, marking its
'done' variable with the AO_DMA_ABORTED bit.
</p></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605144032"></a>2. STM32L DMA Engine</h2></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605143360"></a>2.1. ao_dma_alloc</h3></div></div></div><pre class="programlisting">
uint8_t ao_dma_done[];
void
ao_dma_alloc(uint8_t index);
</pre><p>
Reserve a DMA engine for exclusive use by one
driver.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605141360"></a>2.2. ao_dma_set_transfer</h3></div></div></div><pre class="programlisting">
void
ao_dma_set_transfer(uint8_t id,
void *peripheral,
void *memory,
uint16_t count,
uint32_t ccr);
</pre><p>
Initializes the specified dma engine to copy data between
'peripheral' and 'memory' for 'count' units. 'ccr' is a
value directly out of the STM32L documentation and tells the
DMA engine what the transfer unit size, direction and step
are.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605139104"></a>2.3. ao_dma_set_isr</h3></div></div></div><pre class="programlisting">
void
ao_dma_set_isr(uint8_t index, void (*isr)(int))
</pre><p>
This sets a function to be called when the DMA transfer
completes in lieu of setting the ao_dma_done bits. Use this
when some work needs to be done when the DMA finishes that
cannot wait until user space resumes.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605136944"></a>2.4. ao_dma_start</h3></div></div></div><pre class="programlisting">
void
ao_dma_start(uint8_t id);
</pre><p>
Arm the specified DMA engine and await a signal from either
hardware or software to start transferring data.
'ao_dma_done[index]' is cleared when the DMA is started, and
then receives the AO_DMA_DONE bit on a successful transfer
or the AO_DMA_ABORTED bit if ao_dma_abort was called. Note
that it is possible to get both bits if the transfer was
aborted after it had finished.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605134640"></a>2.5. ao_dma_done_transfer</h3></div></div></div><pre class="programlisting">
void
ao_dma_done_transfer(uint8_t id);
</pre><p>
Signals that a specific DMA engine is done being used. This
allows multiple drivers to use the same DMA engine safely.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605132656"></a>2.6. ao_dma_abort</h3></div></div></div><pre class="programlisting">
void
ao_dma_abort(uint8_t id)
</pre><p>
Terminate any in-progress DMA transaction, marking its
'done' variable with the AO_DMA_ABORTED bit.
</p></div></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="idm46302605130384"></a>Chapter 8. Stdio interface</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#idm46302605128880">1. putchar</a></span></dt><dt><span class="section"><a href="#idm46302605126912">2. getchar</a></span></dt><dt><span class="section"><a href="#idm46302605124816">3. flush</a></span></dt><dt><span class="section"><a href="#idm46302605122784">4. ao_add_stdio</a></span></dt></dl></div><p>
AltOS offers a stdio interface over USB, serial and the RF
packet link. This provides for control of the device locally or
remotely. This is hooked up to the stdio functions by providing
the standard putchar/getchar/flush functions. These
automatically multiplex the available communication channels;
output is always delivered to the channel which provided the
most recent input.
</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605128880"></a>1. putchar</h2></div></div></div><pre class="programlisting">
void
putchar(char c)
</pre><p>
Delivers a single character to the current console
device.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605126912"></a>2. getchar</h2></div></div></div><pre class="programlisting">
char
getchar(void)
</pre><p>
Reads a single character from any of the available
console devices. The current console device is set to
that which delivered this character. This blocks until
a character is available.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605124816"></a>3. flush</h2></div></div></div><pre class="programlisting">
void
flush(void)
</pre><p>
Flushes the current console device output buffer. Any
pending characters will be delivered to the target device.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605122784"></a>4. ao_add_stdio</h2></div></div></div><pre class="programlisting">
void
ao_add_stdio(char (*pollchar)(void),
void (*putchar)(char),
void (*flush)(void))
</pre><p>
This adds another console device to the available
list.
</p><p>
'pollchar' returns either an available character or
AO_READ_AGAIN if none is available. Significantly, it does
not block. The device driver must set 'ao_stdin_ready' to
1 and call ao_wakeup(&ao_stdin_ready) when it receives
input to tell getchar that more data is available, at
which point 'pollchar' will be called again.
</p><p>
'putchar' queues a character for output, flushing if the output buffer is
full. It may block in this case.
</p><p>
'flush' forces the output buffer to be flushed. It may
block until the buffer is delivered, but it is not
required to do so.
</p></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="idm46302605118752"></a>Chapter 9. Command line interface</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#idm46302605117344">1. ao_cmd_register</a></span></dt><dt><span class="section"><a href="#idm46302605108608">2. ao_cmd_lex</a></span></dt><dt><span class="section"><a href="#idm46302605106528">3. ao_cmd_put16</a></span></dt><dt><span class="section"><a href="#idm46302605104688">4. ao_cmd_put8</a></span></dt><dt><span class="section"><a href="#idm46302605102800">5. ao_cmd_white</a></span></dt><dt><span class="section"><a href="#idm46302605100736">6. ao_cmd_hex</a></span></dt><dt><span class="section"><a href="#idm46302605098688">7. ao_cmd_decimal</a></span></dt><dt><span class="section"><a href="#idm46302605096592">8. ao_match_word</a></span></dt><dt><span class="section"><a href="#idm46302605094512">9. ao_cmd_init</a></span></dt></dl></div><p>
AltOS includes a simple command line parser which is hooked up
to the stdio interfaces permitting remote control of the device
over USB, serial or the RF link as desired. Each command uses a
single character to invoke it, the remaining characters on the
line are available as parameters to the command.
</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605117344"></a>1. ao_cmd_register</h2></div></div></div><pre class="programlisting">
void
ao_cmd_register(__code struct ao_cmds *cmds)
</pre><p>
This registers a set of commands with the command
parser. There is a fixed limit on the number of command
sets, the system will panic if too many are registered.
Each command is defined by a struct ao_cmds entry:
</p><pre class="programlisting">
struct ao_cmds {
char cmd;
void (*func)(void);
const char *help;
};
</pre><p>
'cmd' is the character naming the command. 'func' is the
function to invoke and 'help' is a string displayed by the
'?' command. Syntax errors found while executing 'func'
should be indicated by modifying the global ao_cmd_status
variable with one of the following values:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term">ao_cmd_success</span></dt><dd><p>
The command was parsed successfully. There is no
need to assign this value, it is the default.
</p></dd><dt><span class="term">ao_cmd_lex_error</span></dt><dd><p>
A token in the line was invalid, such as a number
containing invalid characters. The low-level
lexing functions already assign this value as needed.
</p></dd><dt><span class="term">ao_syntax_error</span></dt><dd><p>
The command line is invalid for some reason other
than invalid tokens.
</p></dd></dl></div><p>
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605108608"></a>2. ao_cmd_lex</h2></div></div></div><pre class="programlisting">
void
ao_cmd_lex(void);
</pre><p>
This gets the next character out of the command line
buffer and sticks it into ao_cmd_lex_c. At the end of the
line, ao_cmd_lex_c will get a newline ('\n') character.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605106528"></a>3. ao_cmd_put16</h2></div></div></div><pre class="programlisting">
void
ao_cmd_put16(uint16_t v);
</pre><p>
Writes 'v' as four hexadecimal characters.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605104688"></a>4. ao_cmd_put8</h2></div></div></div><pre class="programlisting">
void
ao_cmd_put8(uint8_t v);
</pre><p>
Writes 'v' as two hexadecimal characters.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605102800"></a>5. ao_cmd_white</h2></div></div></div><pre class="programlisting">
void
ao_cmd_white(void)
</pre><p>
This skips whitespace by calling ao_cmd_lex while
ao_cmd_lex_c is either a space or tab. It does not skip
any characters if ao_cmd_lex_c already non-white.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605100736"></a>6. ao_cmd_hex</h2></div></div></div><pre class="programlisting">
void
ao_cmd_hex(void)
</pre><p>
This reads a 16-bit hexadecimal value from the command
line with optional leading whitespace. The resulting value
is stored in ao_cmd_lex_i;
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605098688"></a>7. ao_cmd_decimal</h2></div></div></div><pre class="programlisting">
void
ao_cmd_decimal(void)
</pre><p>
This reads a 32-bit decimal value from the command
line with optional leading whitespace. The resulting value
is stored in ao_cmd_lex_u32 and the low 16 bits are stored
in ao_cmd_lex_i;
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605096592"></a>8. ao_match_word</h2></div></div></div><pre class="programlisting">
uint8_t
ao_match_word(__code char *word)
</pre><p>
This checks to make sure that 'word' occurs on the command
line. It does not skip leading white space. If 'word' is
found, then 1 is returned. Otherwise, ao_cmd_status is set to
ao_cmd_syntax_error and 0 is returned.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605094512"></a>9. ao_cmd_init</h2></div></div></div><pre class="programlisting">
void
ao_cmd_init(void
</pre><p>
Initializes the command system, setting up the built-in
commands and adding a task to run the command processing
loop. It should be called by 'main' before ao_start_scheduler.
</p></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="idm46302605092288"></a>Chapter 10. USB target device</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#idm46302605090064">1. ao_usb_flush</a></span></dt><dt><span class="section"><a href="#idm46302605087920">2. ao_usb_putchar</a></span></dt><dt><span class="section"><a href="#idm46302605085744">3. ao_usb_pollchar</a></span></dt><dt><span class="section"><a href="#idm46302605083600">4. ao_usb_getchar</a></span></dt><dt><span class="section"><a href="#idm46302605081584">5. ao_usb_disable</a></span></dt><dt><span class="section"><a href="#idm46302605078752">6. ao_usb_enable</a></span></dt><dt><span class="section"><a href="#idm46302605076640">7. ao_usb_init</a></span></dt></dl></div><p>
AltOS contains a full-speed USB target device driver. It can be
programmed to offer any kind of USB target, but to simplify
interactions with a variety of operating systems, AltOS provides
only a single target device profile, that of a USB modem which
has native drivers for Linux, Windows and Mac OS X. It would be
easy to change the code to provide an alternate target device if
necessary.
</p><p>
To the rest of the system, the USB device looks like a simple
two-way byte stream. It can be hooked into the command line
interface if desired, offering control of the device over the
USB link. Alternatively, the functions can be accessed directly
to provide for USB-specific I/O.
</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605090064"></a>1. ao_usb_flush</h2></div></div></div><pre class="programlisting">
void
ao_usb_flush(void);
</pre><p>
Flushes any pending USB output. This queues an 'IN' packet
to be delivered to the USB host if there is pending data,
or if the last IN packet was full to indicate to the host
that there isn't any more pending data available.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605087920"></a>2. ao_usb_putchar</h2></div></div></div><pre class="programlisting">
void
ao_usb_putchar(char c);
</pre><p>
If there is a pending 'IN' packet awaiting delivery to the
host, this blocks until that has been fetched. Then, this
adds a byte to the pending IN packet for delivery to the
USB host. If the USB packet is full, this queues the 'IN'
packet for delivery.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605085744"></a>3. ao_usb_pollchar</h2></div></div></div><pre class="programlisting">
char
ao_usb_pollchar(void);
</pre><p>
If there are no characters remaining in the last 'OUT'
packet received, this returns AO_READ_AGAIN. Otherwise, it
returns the next character, reporting to the host that it
is ready for more data when the last character is gone.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605083600"></a>4. ao_usb_getchar</h2></div></div></div><pre class="programlisting">
char
ao_usb_getchar(void);
</pre><p>
This uses ao_pollchar to receive the next character,
blocking while ao_pollchar returns AO_READ_AGAIN.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605081584"></a>5. ao_usb_disable</h2></div></div></div><pre class="programlisting">
void
ao_usb_disable(void);
</pre><p>
This turns off the USB controller. It will no longer
respond to host requests, nor return characters. Calling
any of the i/o routines while the USB device is disabled
is undefined, and likely to break things. Disabling the
USB device when not needed saves power.
</p><p>
Note that neither TeleDongle nor TeleMetrum are able to
signal to the USB host that they have disconnected, so
after disabling the USB device, it's likely that the cable
will need to be disconnected and reconnected before it
will work again.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605078752"></a>6. ao_usb_enable</h2></div></div></div><pre class="programlisting">
void
ao_usb_enable(void);
</pre><p>
This turns the USB controller on again after it has been
disabled. See the note above about needing to physically
remove and re-insert the cable to get the host to
re-initialize the USB link.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605076640"></a>7. ao_usb_init</h2></div></div></div><pre class="programlisting">
void
ao_usb_init(void);
</pre><p>
This turns the USB controller on, adds a task to handle
the control end point and adds the usb I/O functions to
the stdio system. Call this from main before
ao_start_scheduler.
</p></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="idm46302605074416"></a>Chapter 11. Serial peripherals</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#idm46302605072400">1. ao_serial_getchar</a></span></dt><dt><span class="section"><a href="#idm46302605070368">2. ao_serial_putchar</a></span></dt><dt><span class="section"><a href="#idm46302605068400">3. ao_serial_drain</a></span></dt><dt><span class="section"><a href="#idm46302605066400">4. ao_serial_set_speed</a></span></dt><dt><span class="section"><a href="#idm46302605064368">5. ao_serial_init</a></span></dt></dl></div><p>
The CC1111 provides two USART peripherals. AltOS uses one for
asynch serial data, generally to communicate with a GPS device,
and the other for a SPI bus. The UART is configured to operate
in 8-bits, no parity, 1 stop bit framing. The default
configuration has clock settings for 4800, 9600 and 57600 baud
operation. Additional speeds can be added by computing
appropriate clock values.
</p><p>
To prevent loss of data, AltOS provides receive and transmit
fifos of 32 characters each.
</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605072400"></a>1. ao_serial_getchar</h2></div></div></div><pre class="programlisting">
char
ao_serial_getchar(void);
</pre><p>
Returns the next character from the receive fifo, blocking
until a character is received if the fifo is empty.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605070368"></a>2. ao_serial_putchar</h2></div></div></div><pre class="programlisting">
void
ao_serial_putchar(char c);
</pre><p>
Adds a character to the transmit fifo, blocking if the
fifo is full. Starts transmitting characters.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605068400"></a>3. ao_serial_drain</h2></div></div></div><pre class="programlisting">
void
ao_serial_drain(void);
</pre><p>
Blocks until the transmit fifo is empty. Used internally
when changing serial speeds.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605066400"></a>4. ao_serial_set_speed</h2></div></div></div><pre class="programlisting">
void
ao_serial_set_speed(uint8_t speed);
</pre><p>
Changes the serial baud rate to one of
AO_SERIAL_SPEED_4800, AO_SERIAL_SPEED_9600 or
AO_SERIAL_SPEED_57600. This first flushes the transmit
fifo using ao_serial_drain.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605064368"></a>5. ao_serial_init</h2></div></div></div><pre class="programlisting">
void
ao_serial_init(void)
</pre><p>
Initializes the serial peripheral. Call this from 'main'
before jumping to ao_start_scheduler. The default speed
setting is AO_SERIAL_SPEED_4800.
</p></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="idm46302605062176"></a>Chapter 12. CC1111 Radio peripheral</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#idm46302605061504">1. Radio Introduction</a></span></dt><dt><span class="section"><a href="#idm46302605054896">2. ao_radio_set_telemetry</a></span></dt><dt><span class="section"><a href="#idm46302605052800">3. ao_radio_set_packet</a></span></dt><dt><span class="section"><a href="#idm46302605050704">4. ao_radio_set_rdf</a></span></dt><dt><span class="section"><a href="#idm46302605048576">5. ao_radio_idle</a></span></dt><dt><span class="section"><a href="#idm46302605046640">6. ao_radio_get</a></span></dt><dt><span class="section"><a href="#idm46302605044720">7. ao_radio_put</a></span></dt><dt><span class="section"><a href="#idm46302605042944">8. ao_radio_abort</a></span></dt><dt><span class="section"><a href="#idm46302605040992">9. Radio Telemetry</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302605039728">9.1. ao_radio_send</a></span></dt><dt><span class="section"><a href="#idm46302605037568">9.2. ao_radio_recv</a></span></dt></dl></dd><dt><span class="section"><a href="#idm46302605035168">10. Radio Direction Finding</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302605034048">10.1. ao_radio_rdf</a></span></dt></dl></dd><dt><span class="section"><a href="#idm46302605032016">11. Radio Packet Mode</a></span></dt><dd><dl><dt><span class="section"><a href="#idm46302605030736">11.1. ao_packet_putchar</a></span></dt><dt><span class="section"><a href="#idm46302605028624">11.2. ao_packet_pollchar</a></span></dt><dt><span class="section"><a href="#idm46302605026656">11.3. ao_packet_slave_start</a></span></dt><dt><span class="section"><a href="#idm46302605024768">11.4. ao_packet_slave_stop</a></span></dt><dt><span class="section"><a href="#idm46302605022912">11.5. ao_packet_slave_init</a></span></dt><dt><span class="section"><a href="#idm46302605020944">11.6. ao_packet_master_init</a></span></dt></dl></dd></dl></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605061504"></a>1. Radio Introduction</h2></div></div></div><p>
The CC1111 radio transceiver sends and receives digital packets
with forward error correction and detection. The AltOS driver is
fairly specific to the needs of the TeleMetrum and TeleDongle
devices, using it for other tasks may require customization of
the driver itself. There are three basic modes of operation:
</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
Telemetry mode. In this mode, TeleMetrum transmits telemetry
frames at a fixed rate. The frames are of fixed size. This
is strictly a one-way communication from TeleMetrum to
TeleDongle.
</p></li><li class="listitem"><p>
Packet mode. In this mode, the radio is used to create a
reliable duplex byte stream between TeleDongle and
TeleMetrum. This is an asymmetrical protocol with
TeleMetrum only transmitting in response to a packet sent
from TeleDongle. Thus getting data from TeleMetrum to
TeleDongle requires polling. The polling rate is adaptive,
when no data has been received for a while, the rate slows
down. The packets are checked at both ends and invalid
data are ignored.
</p><p>
On the TeleMetrum side, the packet link is hooked into the
stdio mechanism, providing an alternate data path for the
command processor. It is enabled when the unit boots up in
'idle' mode.
</p><p>
On the TeleDongle side, the packet link is enabled with a
command; data from the stdio package is forwarded over the
packet link providing a connection from the USB command
stream to the remote TeleMetrum device.
</p></li><li class="listitem"><p>
Radio Direction Finding mode. In this mode, TeleMetrum
constructs a special packet that sounds like an audio tone
when received by a conventional narrow-band FM
receiver. This is designed to provide a beacon to track
the device when other location mechanisms fail.
</p></li></ol></div><p>
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605054896"></a>2. ao_radio_set_telemetry</h2></div></div></div><pre class="programlisting">
void
ao_radio_set_telemetry(void);
</pre><p>
Configures the radio to send or receive telemetry
packets. This includes packet length, modulation scheme and
other RF parameters. It does not include the base frequency
or channel though. Those are set at the time of transmission
or reception, in case the values are changed by the user.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605052800"></a>3. ao_radio_set_packet</h2></div></div></div><pre class="programlisting">
void
ao_radio_set_packet(void);
</pre><p>
Configures the radio to send or receive packet data. This
includes packet length, modulation scheme and other RF
parameters. It does not include the base frequency or
channel though. Those are set at the time of transmission or
reception, in case the values are changed by the user.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605050704"></a>4. ao_radio_set_rdf</h2></div></div></div><pre class="programlisting">
void
ao_radio_set_rdf(void);
</pre><p>
Configures the radio to send RDF 'packets'. An RDF 'packet'
is a sequence of hex 0x55 bytes sent at a base bit rate of
2kbps using a 5kHz deviation. All of the error correction
and data whitening logic is turned off so that the resulting
modulation is received as a 1kHz tone by a conventional 70cm
FM audio receiver.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605048576"></a>5. ao_radio_idle</h2></div></div></div><pre class="programlisting">
void
ao_radio_idle(void);
</pre><p>
Sets the radio device to idle mode, waiting until it reaches
that state. This will terminate any in-progress transmit or
receive operation.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605046640"></a>6. ao_radio_get</h2></div></div></div><pre class="programlisting">
void
ao_radio_get(void);
</pre><p>
Acquires the radio mutex and then configures the radio
frequency using the global radio calibration and channel
values.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605044720"></a>7. ao_radio_put</h2></div></div></div><pre class="programlisting">
void
ao_radio_put(void);
</pre><p>
Releases the radio mutex.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605042944"></a>8. ao_radio_abort</h2></div></div></div><pre class="programlisting">
void
ao_radio_abort(void);
</pre><p>
Aborts any transmission or reception process by aborting the
associated DMA object and calling ao_radio_idle to terminate
the radio operation.
</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605040992"></a>9. Radio Telemetry</h2></div></div></div><p>
In telemetry mode, you can send or receive a telemetry
packet. The data from receiving a packet also includes the RSSI
and status values supplied by the receiver. These are added
after the telemetry data.
</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605039728"></a>9.1. ao_radio_send</h3></div></div></div><pre class="programlisting">
void
ao_radio_send(__xdata struct ao_telemetry *telemetry);
</pre><p>
This sends the specific telemetry packet, waiting for the
transmission to complete. The radio must have been set to
telemetry mode. This function calls ao_radio_get() before
sending, and ao_radio_put() afterwards, to correctly
serialize access to the radio device.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605037568"></a>9.2. ao_radio_recv</h3></div></div></div><pre class="programlisting">
void
ao_radio_recv(__xdata struct ao_radio_recv *radio);
</pre><p>
This blocks waiting for a telemetry packet to be received.
The radio must have been set to telemetry mode. This
function calls ao_radio_get() before receiving, and
ao_radio_put() afterwards, to correctly serialize access
to the radio device. This returns non-zero if a packet was
received, or zero if the operation was aborted (from some
other task calling ao_radio_abort()).
</p></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605035168"></a>10. Radio Direction Finding</h2></div></div></div><p>
In radio direction finding mode, there's just one function to
use
</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605034048"></a>10.1. ao_radio_rdf</h3></div></div></div><pre class="programlisting">
void
ao_radio_rdf(int ms);
</pre><p>
This sends an RDF packet lasting for the specified amount
of time. The maximum length is 1020 ms.
</p></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idm46302605032016"></a>11. Radio Packet Mode</h2></div></div></div><p>
Packet mode is asymmetrical and is configured at compile time
for either master or slave mode (but not both). The basic I/O
functions look the same at both ends, but the internals are
different, along with the initialization steps.
</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605030736"></a>11.1. ao_packet_putchar</h3></div></div></div><pre class="programlisting">
void
ao_packet_putchar(char c);
</pre><p>
If the output queue is full, this first blocks waiting for
that data to be delivered. Then, queues a character for
packet transmission. On the master side, this will
transmit a packet if the output buffer is full. On the
slave side, any pending data will be sent the next time
the master polls for data.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605028624"></a>11.2. ao_packet_pollchar</h3></div></div></div><pre class="programlisting">
char
ao_packet_pollchar(void);
</pre><p>
This returns a pending input character if available,
otherwise returns AO_READ_AGAIN. On the master side, if
this empties the buffer, it triggers a poll for more data.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605026656"></a>11.3. ao_packet_slave_start</h3></div></div></div><pre class="programlisting">
void
ao_packet_slave_start(void);
</pre><p>
This is available only on the slave side and starts a task
to listen for packet data.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605024768"></a>11.4. ao_packet_slave_stop</h3></div></div></div><pre class="programlisting">
void
ao_packet_slave_stop(void);
</pre><p>
Disables the packet slave task, stopping the radio receiver.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605022912"></a>11.5. ao_packet_slave_init</h3></div></div></div><pre class="programlisting">
void
ao_packet_slave_init(void);
</pre><p>
Adds the packet stdio functions to the stdio package so
that when packet slave mode is enabled, characters will
get send and received through the stdio functions.
</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="idm46302605020944"></a>11.6. ao_packet_master_init</h3></div></div></div><pre class="programlisting">
void
ao_packet_master_init(void);
</pre><p>
Adds the 'p' packet forward command to start packet mode.
</p></div></div></div></div></body></html>
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