ardupilot/libraries/AP_HAL_AVR/RCInput_APM1.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 APM1RCInput::_pulse_capt[AVR_RC_INPUT_NUM_CHANNELS] = {0};
volatile uint8_t APM1RCInput::_num_channels = 0;
volatile bool APM1RCInput::_new_input = false;
/* private callback for input capture ISR */
void APM1RCInput::_timer4_capt_cb(void) {
static uint16_t icr4_prev;
static uint8_t channel_ctr;
const uint16_t icr4_current = ICR4;
uint16_t pulse_width;
if (icr4_current < icr4_prev) {
/* ICR4 rolls over at TOP=40000 */
pulse_width = icr4_current + 40000 - icr4_prev;
} else {
pulse_width = icr4_current - icr4_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 ) {
_num_channels = channel_ctr;
_new_input = true;
}
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) {
_num_channels = AVR_RC_INPUT_NUM_CHANNELS;
_new_input = true;
}
}
}
icr4_prev = icr4_current;
}
void APM1RCInput::init(void* _isrregistry) {
ISRRegistry* isrregistry = (ISRRegistry*) _isrregistry;
isrregistry->register_signal(ISR_REGISTRY_TIMER4_CAPT, _timer4_capt_cb);
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/* initialize overrides */
clear_overrides();
/* Arduino pin 49 is ICP4 / PL0, timer 4 input capture */
hal.gpio->pinMode(49, HAL_GPIO_INPUT);
/**
* WGM: 1 1 1 1. Fast WPM, TOP is in OCR4A
* COM all disabled
* CS41: prescale by 8 => 0.5us tick
* ICES4: input capture on rising edge
* OCR4A: 40000, 0.5us tick => 2ms period / 50hz freq for outbound
* fast PWM.
*/
uint8_t oldSREG = SREG;
cli();
/* Timer cleanup before configuring */
TCNT4 = 0;
TIFR4 = 0;
/* Set timer 8x prescaler fast PWM mode toggle compare at OCRA with rising edge input capture */
TCCR4A = _BV(WGM40) | _BV(WGM41);
TCCR4B |= _BV(WGM43) | _BV(WGM42) | _BV(CS41) | _BV(ICES4);
OCR4A = 40000 - 1; // -1 to correct for wrap
/* OCR4B and OCR4C will be used by RCOutput_APM1. Init to 0xFFFF to prevent premature PWM output */
OCR4B = 0xFFFF;
OCR4C = 0xFFFF;
/* Enable input capture interrupt */
TIMSK4 |= _BV(ICIE4);
SREG = oldSREG;
}
bool APM1RCInput::new_input() { return _new_input; }
uint8_t APM1RCInput::num_channels() { return _num_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 APM1RCInput::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*/
uint8_t oldSREG = SREG;
cli();
uint16_t capt = _pulse_capt[ch];
SREG = oldSREG;
_new_input = false;
/* 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 APM1RCInput::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 */
uint8_t oldSREG = SREG;
cli();
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for (uint8_t i = 0; i < len; i++) {
periods[i] = _pulse_capt[i];
}
SREG = oldSREG;
/* Outside of critical section, do the math (in place) to scale and
* constrain the pulse. */
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for (uint8_t 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];
}
}
_new_input = false;
return _num_channels;
}
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bool APM1RCInput::set_overrides(int16_t *overrides, uint8_t len) {
bool res = false;
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for (uint8_t i = 0; i < len; i++) {
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res |= set_override(i, overrides[i]);
}
return res;
}
bool APM1RCInput::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) {
_new_input = true;
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return true;
}
}
return false;
}
void APM1RCInput::clear_overrides() {
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for (uint8_t i = 0; i < AVR_RC_INPUT_NUM_CHANNELS; i++) {
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_override[i] = 0;
}
}
#endif