ardupilot/libraries/AP_HAL_AVR/RCInput_APM2.cpp

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#include <AP_HAL.h>
#if (CONFIG_HAL_BOARD == HAL_BOARD_APM1 || CONFIG_HAL_BOARD == HAL_BOARD_APM2)
#include <avr/io.h>
#include <avr/interrupt.h>
#include <AP_HAL.h>
#include <AP_HAL_AVR.h>
#include "RCInput.h"
#include "utility/ISRRegistry.h"
using namespace AP_HAL;
using namespace AP_HAL_AVR;
extern const HAL& hal;
/* private variables to communicate with input capture isr */
volatile uint16_t APM2RCInput::_pulse_capt[AVR_RC_INPUT_NUM_CHANNELS] = {0};
volatile uint8_t APM2RCInput::_valid_channels = 0;
/* private callback for input capture ISR */
void APM2RCInput::_timer5_capt_cb(void) {
static uint16_t icr5_prev;
static uint8_t channel_ctr;
const uint16_t icr5_current = ICR5;
uint16_t pulse_width;
if (icr5_current < icr5_prev) {
/* ICR5 rolls over at TOP=40000 */
pulse_width = icr5_current + 40000 - icr5_prev;
} else {
pulse_width = icr5_current - icr5_prev;
}
if (pulse_width > 8000) {
// sync pulse detected. Pass through values if at least a minimum number of channels received
if( channel_ctr >= AVR_RC_INPUT_MIN_CHANNELS ) {
_valid_channels = channel_ctr;
}
channel_ctr = 0;
} else {
if (channel_ctr < AVR_RC_INPUT_NUM_CHANNELS) {
_pulse_capt[channel_ctr] = pulse_width;
channel_ctr++;
if (channel_ctr == AVR_RC_INPUT_NUM_CHANNELS) {
_valid_channels = AVR_RC_INPUT_NUM_CHANNELS;
}
}
}
icr5_prev = icr5_current;
}
void APM2RCInput::init(void* _isrregistry) {
ISRRegistry* isrregistry = (ISRRegistry*) _isrregistry;
isrregistry->register_signal(ISR_REGISTRY_TIMER5_CAPT, _timer5_capt_cb);
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/* initialize overrides */
clear_overrides();
/* Arduino pin 48 is ICP5 / PL1, timer 5 input capture */
hal.gpio->pinMode(48, GPIO_INPUT);
/**
* WGM: 1 1 1 1. Fast WPM, TOP is in OCR5A
* COM all disabled
* CS51: prescale by 8 => 0.5us tick
* ICES5: input capture on rising edge
* OCR5A: 40000, 0.5us tick => 2ms period / 50hz freq for outbound
* fast PWM.
*/
TCCR5A = _BV(WGM50) | _BV(WGM51);
TCCR5B = _BV(WGM53) | _BV(WGM52) | _BV(CS51) | _BV(ICES5);
OCR5A = 40000;
/* OCR5B and OCR5C will be used by RCOutput_APM2. init to nil output */
OCR5B = 0xFFFF;
OCR5C = 0xFFFF;
/* Enable input capture interrupt */
TIMSK5 |= _BV(ICIE5);
}
uint8_t APM2RCInput::valid_channels() { return _valid_channels; }
/* constrain captured pulse to be between min and max pulsewidth. */
static inline uint16_t constrain_pulse(uint16_t p) {
if (p > RC_INPUT_MAX_PULSEWIDTH) return RC_INPUT_MAX_PULSEWIDTH;
if (p < RC_INPUT_MIN_PULSEWIDTH) return RC_INPUT_MIN_PULSEWIDTH;
return p;
}
uint16_t APM2RCInput::read(uint8_t ch) {
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/* constrain ch */
if (ch >= AVR_RC_INPUT_NUM_CHANNELS) return 0;
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/* grab channel from isr's memory in critical section*/
cli();
uint16_t capt = _pulse_capt[ch];
sei();
_valid_channels = 0;
/* scale _pulse_capt from 0.5us units to 1us units. */
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uint16_t pulse = constrain_pulse(capt >> 1);
/* Check for override */
uint16_t over = _override[ch];
return (over == 0) ? pulse : over;
}
uint8_t APM2RCInput::read(uint16_t* periods, uint8_t len) {
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/* constrain len */
if (len > AVR_RC_INPUT_NUM_CHANNELS) { len = AVR_RC_INPUT_NUM_CHANNELS; }
/* grab channels from isr's memory in critical section */
cli();
for (int i = 0; i < len; i++) {
periods[i] = _pulse_capt[i];
}
sei();
/* Outside of critical section, do the math (in place) to scale and
* constrain the pulse. */
for (int i = 0; i < len; i++) {
/* scale _pulse_capt from 0.5us units to 1us units. */
periods[i] = constrain_pulse(periods[i] >> 1);
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/* check for override */
if (_override[i] != 0) {
periods[i] = _override[i];
}
}
uint8_t v = _valid_channels;
_valid_channels = 0;
return v;
}
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bool APM2RCInput::set_overrides(int16_t *overrides, uint8_t len) {
bool res = false;
for (int i = 0; i < len; i++) {
res |= set_override(i, overrides[i]);
}
return res;
}
bool APM2RCInput::set_override(uint8_t channel, int16_t override) {
if (override < 0) return false; /* -1: no change. */
if (channel < AVR_RC_INPUT_NUM_CHANNELS) {
_override[channel] = override;
if (override != 0) {
_valid_channels = 1;
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return true;
}
}
return false;
}
void APM2RCInput::clear_overrides() {
for (int i = 0; i < AVR_RC_INPUT_NUM_CHANNELS; i++) {
_override[i] = 0;
}
}
#endif