ardupilot/libraries/AP_WheelEncoder/WheelEncoder_Quadrature.cpp

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/*
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, either version 3 of the License, or
(at your option) any later version.
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, see <http://www.gnu.org/licenses/>.
*/
#include <AP_HAL/AP_HAL.h>
#include "WheelEncoder_Quadrature.h"
#include <GCS_MAVLink/GCS.h>
extern const AP_HAL::HAL& hal;
// constructor
AP_WheelEncoder_Quadrature::AP_WheelEncoder_Quadrature(AP_WheelEncoder &frontend, uint8_t instance, AP_WheelEncoder::WheelEncoder_State &state) :
AP_WheelEncoder_Backend(frontend, instance, state)
{
}
// check if pin has changed and initialise gpio event callback
void AP_WheelEncoder_Quadrature::update_pin(uint8_t &pin,
uint8_t new_pin,
uint8_t &pin_value)
{
if (new_pin == pin) {
// no change
return;
}
// remove old gpio event callback if present
if (pin != (uint8_t)-1 &&
!hal.gpio->detach_interrupt(pin)) {
gcs().send_text(MAV_SEVERITY_WARNING, "WEnc: Failed to detach from pin %u", pin);
// ignore this failure or the user may be stuck
}
pin = new_pin;
// install interrupt handler on rising or falling edge of gpio for pin a
if (new_pin != (uint8_t)-1) {
hal.gpio->pinMode(pin, HAL_GPIO_INPUT);
if (!hal.gpio->attach_interrupt(
pin,
FUNCTOR_BIND_MEMBER(&AP_WheelEncoder_Quadrature::irq_handler,
void,
uint8_t,
bool,
uint32_t),
AP_HAL::GPIO::INTERRUPT_BOTH)) {
gcs().send_text(MAV_SEVERITY_WARNING, "WEnc: Failed to attach to pin %u", pin);
}
pin_value = hal.gpio->read(pin);
}
}
void AP_WheelEncoder_Quadrature::update(void)
{
update_pin(last_pin_a, get_pin_a(), last_pin_a_value);
update_pin(last_pin_b, get_pin_b(), last_pin_b_value);
// disable interrupts to prevent race with irq_handler
void *irqstate = hal.scheduler->disable_interrupts_save();
// copy distance and error count so it is accessible to front end
copy_state_to_frontend(irq_state.distance_count,
irq_state.total_count,
irq_state.error_count,
irq_state.last_reading_ms);
// restore interrupts
hal.scheduler->restore_interrupts(irqstate);
}
// convert pin a and pin b state to a wheel encoder phase
uint8_t AP_WheelEncoder_Quadrature::pin_ab_to_phase(bool pin_a, bool pin_b)
{
if (!pin_a) {
if (!pin_b) {
// A = 0, B = 0
return 0;
} else {
// A = 0, B = 1
return 1;
}
} else {
if (!pin_b) {
// A = 1, B = 0
return 3;
} else {
// A = 1, B = 1
return 2;
}
}
return (uint8_t)pin_a << 1 | (uint8_t)pin_b;
}
void AP_WheelEncoder_Quadrature::update_phase_and_error_count()
{
// convert pin state before and after to phases
uint8_t phase_after = pin_ab_to_phase(last_pin_a_value, last_pin_b_value);
// look for invalid changes
uint8_t step_forward = irq_state.phase < 3 ? irq_state.phase+1 : 0;
uint8_t step_back = irq_state.phase > 0 ? irq_state.phase-1 : 3;
if (phase_after == step_forward) {
irq_state.phase = phase_after;
irq_state.distance_count++;
} else if (phase_after == step_back) {
irq_state.phase = phase_after;
irq_state.distance_count--;
} else {
irq_state.error_count++;
}
irq_state.total_count++;
}
void AP_WheelEncoder_Quadrature::irq_handler(uint8_t pin,
bool pin_value,
uint32_t timestamp)
{
// sanity check
if (last_pin_a == 0 || last_pin_b == 0) {
return;
}
// update distance and error counts
if (pin == last_pin_a) {
last_pin_a_value = pin_value;
} else if (pin == last_pin_b) {
last_pin_b_value = pin_value;
} else {
return;
};
update_phase_and_error_count();
// record update time
irq_state.last_reading_ms = timestamp;
}