mirror of https://github.com/ArduPilot/ardupilot
109 lines
3.0 KiB
C++
109 lines
3.0 KiB
C++
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include <AP_HAL.h>
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#include <AP_HAL_AVR.h>
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#include "RCInput.h"
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#include "utility/ISRRegistry.h"
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using namespace AP_HAL;
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using namespace AP_HAL_AVR;
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extern const HAL& hal;
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/* private variables to communicate with input capture isr */
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volatile uint16_t APM2RCInput::_pulse_capt[AVR_RC_INPUT_NUM_CHANNELS] = {0};
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volatile uint8_t APM2RCInput::_valid = 0;
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/* private callback for input capture ISR */
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void APM2RCInput::_timer5_capt_cb(void) {
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static uint16_t icr5_prev;
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static uint8_t channel_ctr;
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const uint16_t icr5_current = ICR5;
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uint16_t pulse_width;
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if (icr5_current < icr5_prev) {
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/* ICR5 rolls over at TOP=40000 */
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pulse_width = icr5_current + 40000 - icr5_prev;
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} else {
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pulse_width = icr5_current - icr5_prev;
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}
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if (pulse_width > 8000) {
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/* sync pulse detected */
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channel_ctr = 0;
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} else {
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if (channel_ctr < AVR_RC_INPUT_NUM_CHANNELS) {
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_pulse_capt[channel_ctr] = pulse_width;
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channel_ctr++;
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if (channel_ctr == AVR_RC_INPUT_NUM_CHANNELS) {
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_valid = AVR_RC_INPUT_NUM_CHANNELS;
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}
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}
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}
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icr5_prev = icr5_current;
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}
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void APM2RCInput::init(void* _isrregistry) {
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ISRRegistry* isrregistry = (ISRRegistry*) _isrregistry;
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isrregistry->register_signal(ISR_REGISTRY_TIMER5_CAPT, _timer5_capt_cb);
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/* Arduino pin 48 is ICP5 / PL1, timer 5 input capture */
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hal.gpio->pinMode(48, GPIO_INPUT);
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/**
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* WGM: 1 1 1 1. Fast WPM, TOP is in OCR5A
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* COM all disabled
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* CS51: prescale by 8 => 0.5us tick
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* ICES5: input capture on rising edge
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* OCR5A: 40000, 0.5us tick => 2ms period / 50hz freq for outbound
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* fast PWM.
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*/
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TCCR5A = _BV(WGM50) | _BV(WGM51);
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TCCR5B = _BV(WGM53) | _BV(WGM52) | _BV(CS51) | _BV(ICES5);
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OCR5A = 40000;
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/* OCR5B and OCR5C will be used by RCOutput_APM2. init to nil output */
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OCR5B = 0xFFFF;
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OCR5C = 0xFFFF;
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/* Enable input capture interrupt */
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TIMSK5 |= _BV(ICIE5);
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}
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uint8_t APM2RCInput::valid() { return _valid; }
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/* constrain captured pulse to be between min and max pulsewidth. */
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static inline uint16_t constrain_pulse(uint16_t p) {
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if (p > RC_INPUT_MAX_PULSEWIDTH) return RC_INPUT_MAX_PULSEWIDTH;
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if (p < RC_INPUT_MIN_PULSEWIDTH) return RC_INPUT_MIN_PULSEWIDTH;
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return p;
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}
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uint16_t APM2RCInput::read(uint8_t ch) {
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cli();
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uint16_t capt = _pulse_capt[ch];
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sei();
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_valid = 0;
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/* scale _pulse_capt from 0.5us units to 1us units. */
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return constrain_pulse(capt >> 1);
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}
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uint8_t APM2RCInput::read(uint16_t* periods, uint8_t len) {
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cli();
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for (int i = 0; i < len; i++) {
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periods[i] = _pulse_capt[i];
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}
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sei();
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/* Outside of critical section, do the math (in place) to scale and
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* constrain the pulse. */
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for (int i = 0; i < len; i++) {
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/* scale _pulse_capt from 0.5us units to 1us units. */
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periods[i] = constrain_pulse(periods[i] >> 1);
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}
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uint8_t v = _valid;
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_valid = 0;
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return v;
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}
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