diff options
Diffstat (limited to 'doc/system-operation.inc')
| -rw-r--r-- | doc/system-operation.inc | 307 |
1 files changed, 307 insertions, 0 deletions
diff --git a/doc/system-operation.inc b/doc/system-operation.inc new file mode 100644 index 00000000..e68b2acb --- /dev/null +++ b/doc/system-operation.inc @@ -0,0 +1,307 @@ +[appendix] +== System Operation + + === Firmware Modes + + The AltOS firmware build for the altimeters has two + fundamental modes, “idle” and “flight”. Which of these modes + the firmware operates in is determined at start up + time. + ifdef::telemetrum,telemega,easymega[] + For + TeleMetrum, TeleMega and EasyMega, which have accelerometers, the mode is + controlled by the orientation of the + rocket (well, actually the board, of course...) at the time + power is switched on. If the rocket is “nose up”, then + the flight computer assumes it's on a rail or rod being prepared for + launch, so the firmware chooses flight mode. However, if the + rocket is more or less horizontal, the firmware instead enters + idle mode. + endif::telemetrum,telemega,easymega[] + Since + EasyMini doesn't + have an + accelerometer we can use to determine orientation, “idle” mode + is selected if the board is connected via USB to a computer, + otherwise the board enters “flight” mode. + ifdef::telemini[] + TeleMini v1.0 + selects “idle” mode if it receives a command packet within the + first five seconds of operation. + endif::telemini[] + + At power on, the altimeter will beep out the battery voltage + to the nearest tenth of a volt. Each digit is represented by + a sequence of short “dit” beeps, with a pause between + digits. A zero digit is represented with one long “dah” + beep. Then there will be a short pause while the altimeter + completes initialization and self test, and decides which mode + to enter next. + + In flight or “pad” mode, the altimeter engages the flight + state machine, goes into transmit-only mode to send telemetry, + and waits for launch to be detected. Flight mode is indicated + by an “di-dah-dah-dit” (“P” for pad) on the beeper or lights, + followed by beeps or flashes indicating the state of the + pyrotechnic igniter continuity. One beep/flash indicates + apogee continuity, two beeps/flashes indicate main continuity, + three beeps/flashes indicate both apogee and main continuity, + and one longer “brap” sound which is made by rapidly + alternating between two tones indicates no continuity. For a + dual deploy flight, make sure you're getting three beeps or + flashes before launching! For apogee-only or motor eject + flights, do what makes sense. + + If idle mode is entered, you will hear an audible “di-dit” or + see two short flashes (“I” for idle), and the flight state + machine is disengaged, thus no ejection charges will fire. + ifdef::radio[] + The altimeters also listen for the radio link when in idle + mode for requests sent via TeleDongle. Commands can be issued + in idle mode over either USB or the radio link + equivalently. + ifdef::telemini[TeleMini v1.0 only has the radio link.] + endif::radio[] + Idle mode is useful for configuring the altimeter, for + extracting data from the on-board storage chip after + flight, and for ground testing pyro charges. + + In “Idle” and “Pad” modes, once the mode indication + beeps/flashes and continuity indication has been sent, if + there is no space available to log the flight in on-board + memory, the flight computer will emit a warbling tone (much + slower than the “no continuity tone”) + + See <<_understanding_beeps>> for a summary of all of + the audio signals used. + + Once landed, the flight computer will signal that by emitting + the “Landed” sound described above, after which it will beep + out the apogee height (in meters). Each digit is represented + by a sequence of short “dit” beeps, with a pause between + digits. A zero digit is represented with one long “dah” + beep. The flight computer will continue to report landed mode + and beep out the maximum height until turned off. + + ifdef::telemetrum,telemega,easymega[] + One “neat trick” of particular value when TeleMetrum, TeleMega + or EasyMega are used with + very large air-frames, is that you can power the board up while the + rocket is horizontal, such that it comes up in idle mode. Then you can + raise the air-frame to launch position, and issue a 'reset' command + via TeleDongle over the radio link to cause the altimeter to reboot and + come up in flight mode. This is much safer than standing on the top + step of a rickety step-ladder or hanging off the side of a launch + tower with a screw-driver trying to turn on your avionics before + installing igniters! + endif::telemetrum,telemega,easymega[] + + ifdef::telemini[] + TeleMini v1.0 is configured solely via the radio link. Of course, that + means you need to know the TeleMini radio configuration values + or you won't be able to communicate with it. For situations + when you don't have the radio configuration values, TeleMini v1.0 + offers an 'emergency recovery' mode. In this mode, TeleMini is + configured as follows: + + + * Sets the radio frequency to 434.550MHz + * Sets the radio calibration back to the factory value. + * Sets the callsign to N0CALL + * Does not go to 'pad' mode after five seconds. + + To get into 'emergency recovery' mode, first find the row of + four small holes opposite the switch wiring. Using a short + piece of small gauge wire, connect the outer two holes + together, then power TeleMini up. Once the red LED is lit, + disconnect the wire and the board should signal that it's in + 'idle' mode after the initial five second startup + period. + endif::telemini[] + + ifdef::gps[] + === GPS + + TeleMetrum and TeleMega include a complete GPS receiver. A + complete explanation of how GPS works is beyond the scope of + this manual, but the bottom line is that the GPS receiver + needs to lock onto at least four satellites to obtain a solid + 3 dimensional position fix and know what time it is. + + The flight computers provide backup power to the GPS chip any time a + battery is connected. This allows the receiver to “warm start” on + the launch rail much faster than if every power-on were a GPS + “cold start”. In typical operations, powering up + on the flight line in idle mode while performing final air-frame + preparation will be sufficient to allow the GPS receiver to cold + start and acquire lock. Then the board can be powered down during + RSO review and installation on a launch rod or rail. When the board + is turned back on, the GPS system should lock very quickly, typically + long before igniter installation and return to the flight line are + complete. + endif::gps[] + + ifdef::radio[] + === Controlling An Altimeter Over The Radio Link + + One of the unique features of the Altus Metrum system is the + ability to create a two way command link between TeleDongle + and an altimeter using the digital radio transceivers + built into each device. This allows you to interact with the + altimeter from afar, as if it were directly connected to the + computer. + + Any operation which can be performed with a flight computer can + either be done with the device directly connected to the + computer via the USB cable, or through the radio + link. TeleMini v1.0 doesn't provide a USB connector and so it is + always communicated with over radio. Select the appropriate + TeleDongle device when the list of devices is presented and + AltosUI will interact with an altimeter over the radio link. + + One oddity in the current interface is how AltosUI selects the + frequency for radio communications. Instead of providing + an interface to specifically configure the frequency, it uses + whatever frequency was most recently selected for the target + TeleDongle device in Monitor Flight mode. If you haven't ever + used that mode with the TeleDongle in question, select the + Monitor Flight button from the top level UI, and pick the + appropriate TeleDongle device. Once the flight monitoring + window is open, select the desired frequency and then close it + down again. All radio communications will now use that frequency. + + * Save Flight Data—Recover flight data from the + rocket without opening it up. + + * Configure altimeter apogee delays, main deploy + heights and additional pyro event conditions to + respond to changing launch conditions. You can also + 'reboot' the altimeter. Use this to remotely enable + the flight computer by turning TeleMetrum or + TeleMega on in “idle” mode, then once the air-frame + is oriented for launch, you can reboot the + altimeter and have it restart in pad mode without + having to climb the scary ladder. + + * Fire Igniters—Test your deployment charges without snaking + wires out through holes in the air-frame. Simply assemble the + rocket as if for flight with the apogee and main charges + loaded, then remotely command the altimeter to fire the + igniters. + + Operation over the radio link for configuring an + altimeter, ground testing igniters, and so forth uses + the same RF frequencies as flight telemetry. To + configure the desired TeleDongle frequency, select the + monitor flight tab, then use the frequency selector + and close the window before performing other desired + radio operations. + + The flight computers only enable radio commanding in + 'idle' mode. TeleMetrum and TeleMega use the + accelerometer to detect which orientation they start + up in, so make sure you have the flight computer lying + horizontally when you turn it on. Otherwise, it will + start in 'pad' mode ready for flight, and will not be + listening for command packets from TeleDongle. + + TeleMini listens for a command packet for five seconds + after first being turned on, if it doesn't hear + anything, it enters 'pad' mode, ready for flight and + will no longer listen for command packets. The easiest + way to connect to TeleMini is to initiate the command + and select the TeleDongle device. At this point, the + TeleDongle will be attempting to communicate with the + TeleMini. Now turn TeleMini on, and it should + immediately start communicating with the TeleDongle + and the desired operation can be performed. + + You can monitor the operation of the radio link by watching the + lights on the devices. The red LED will flash each time a packet + is transmitted, while the green LED will light up on TeleDongle when + it is waiting to receive a packet from the altimeter. + endif::radio[] + + === Ground Testing + + An important aspect of preparing a rocket using electronic deployment + for flight is ground testing the recovery system. + ifdef::radio[] + Thanks + to the bi-directional radio link central to the Altus Metrum system, + this can be accomplished in a TeleMega, TeleMetrum or TeleMini equipped rocket + with less work than you may be accustomed to with other systems. It + can even be fun! + endif::radio[] + + Just prep the rocket for flight, then power up the altimeter + in “idle” + ifdef::telemetrum,telemega,telemini[] + mode (placing air-frame horizontal for TeleMetrum or TeleMega, or + selecting the Configure Altimeter tab for TeleMini). + This will cause + the firmware to go into “idle” mode, in which the normal flight + state machine is disabled and charges will not fire without + manual command. + endif::telemetrum,telemega,telemini[] + ifndef::telemetrum,telemega,telemini[] + mode. + endif::telemetrum,telemega,telemini[] + You can now command the altimeter to fire the apogee + or main charges from a safe distance using your + computer and the Fire Igniter tab to complete ejection testing. + + ifdef::radio[] + === Radio Link + + TeleMetrum, TeleMini and TeleMega all incorporate an + RF transceiver, but it's not a full duplex system; + each end can only be transmitting or receiving at any + given moment. So we had to decide how to manage the + link. + + By design, the altimeter firmware listens for the + radio link when it's in “idle mode”, which allows us + to use the radio link to configure the rocket, do + things like ejection tests, and extract data after a + flight without having to crack open the air-frame. + However, when the board is in “flight mode”, the + altimeter only transmits and doesn't listen at all. + That's because we want to put ultimate priority on + event detection and getting telemetry out of the + rocket through the radio in case the rocket crashes + and we aren't able to extract data later. + + We don't generally use a 'normal packet radio' mode + like APRS because they're just too inefficient. The + GFSK modulation we use is FSK with the base-band + pulses passed through a Gaussian filter before they go + into the modulator to limit the transmitted bandwidth. + When combined with forward error correction and + interleaving, this allows us to have a very robust + 19.2 kilobit data link with only 10-40 milliwatts of + transmit power, a whip antenna in the rocket, and a + hand-held Yagi on the ground. We've had flights to + above 21k feet AGL with great reception, and + calculations suggest we should be good to well over + 40k feet AGL with a 5-element yagi on the ground with + our 10mW units and over 100k feet AGL with the 40mW + devices. We hope to fly boards to higher altitudes + over time, and would of course appreciate customer + feedback on performance in higher altitude flights! + endif::radio[] + + ifdef::gps+radio[] + :aprsdevices: TeleMetrum v2.0 and TeleMega + :configure_section: _configure_altimeter + include::aprs-operation.raw[] + endif::gps+radio[] + + === Configurable Parameters + + Configuring an Altus Metrum altimeter for flight is + very simple. Even on our baro-only TeleMini and + EasyMini boards, the use of a Kalman filter means + there is no need to set a “mach delay”. All of the + configurable parameters can be set using AltosUI. Read + <<_configure_altimeter>> for more information. |