diff options
Diffstat (limited to 'src/avr/ao_pwmin.c')
| -rw-r--r-- | src/avr/ao_pwmin.c | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/src/avr/ao_pwmin.c b/src/avr/ao_pwmin.c new file mode 100644 index 00000000..84397357 --- /dev/null +++ b/src/avr/ao_pwmin.c @@ -0,0 +1,90 @@ +/* + * Copyright © 2012 Robert D. Garbee <robert@gag.com> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; version 2 of the License. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. + */ + +#include "ao.h" +#include "ao_pwmin.h" + +/* + * This code implements a PWM input using ICP3. + * + * The initial use is to measure wind speed in the ULA/Ball summer intern + * project payload developed at Challenger Middle School. + */ + +volatile __data uint16_t ao_icp3_count = 0; +volatile __data uint16_t ao_icp3_last = 0; + +uint16_t ao_icp3(void) +{ + uint16_t v; + ao_arch_critical( + v = ao_icp3_count; + ); + return v; +} + +static void +ao_pwmin_display(void) __reentrant +{ + /* display the most recent value */ + printf("icp 3: %5u\n", ao_icp3()); + +} + + +ISR(TIMER3_CAPT_vect) +{ + + uint8_t lo = ICR3L; + uint8_t hi = ICR3H; + uint16_t ao_icp3_this = (hi <<8) | lo; + + /* handling counter rollovers */ + if (ao_icp3_this >= ao_icp3_last) + ao_icp3_count = ao_icp3_this - ao_icp3_last; + else + ao_icp3_count = ao_icp3_this + (65536 - ao_icp3_last); + ao_icp3_last = ao_icp3_this; +} + +__code struct ao_cmds ao_pwmin_cmds[] = { + { ao_pwmin_display, "p\0PWM input" }, + { 0, NULL }, +}; + +void +ao_pwmin_init(void) +{ + /* do hardware setup here */ + TCCR3A = ((0 << WGM31) | /* normal mode, OCR3A */ + (0 << WGM30)); /* normal mode, OCR3A */ + TCCR3B = ((1 << ICNC3) | /* input capture noise canceler on */ + (0 << ICES3) | /* input capture on falling edge (don't care) */ + (0 << WGM33) | /* normal mode, OCR3A */ + (0 << WGM32) | /* normal mode, OCR3A */ + (3 << CS30)); /* clk/64 from prescaler */ + + + + TIMSK3 = (1 << ICIE3); /* Interrupt on input compare */ + + /* set the spike filter bit in the TCCR3B register */ + + ao_cmd_register(&ao_pwmin_cmds[0]); +} + + |