mirror of https://github.com/ArduPilot/ardupilot
143 lines
4.3 KiB
C++
143 lines
4.3 KiB
C++
/*
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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/*
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* AP_RangeFinder_HC_SR04.cpp - rangefinder for HC_SR04 source
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*
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* https://cdn.sparkfun.com/datasheets/Sensors/Proximity/HCSR04.pdf
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*
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* There are two pins involved - one we attach an interrupt handler
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* to and use for measuring the supplied interval which is
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* proportional to distance.
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*
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* The second pin we use for triggering the ultransonic pulse
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*/
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#include <AP_HAL/AP_HAL.h>
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#include "AP_RangeFinder.h"
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#include "AP_RangeFinder_Params.h"
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#include "AP_RangeFinder_HC_SR04.h"
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#include <GCS_MAVLink/GCS.h>
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extern const AP_HAL::HAL& hal;
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AP_RangeFinder_HC_SR04::AP_RangeFinder_HC_SR04(RangeFinder::RangeFinder_State &_state, AP_RangeFinder_Params &_params) :
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AP_RangeFinder_Backend(_state, _params)
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{
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set_status(RangeFinder::Status::NoData);
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}
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bool AP_RangeFinder_HC_SR04::check_pins()
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{
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check_trigger_pin();
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return check_echo_pin() && trigger_pin > 0;
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}
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void AP_RangeFinder_HC_SR04::check_trigger_pin()
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{
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if (params.stop_pin == trigger_pin) {
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// no change
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return;
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}
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trigger_pin = params.stop_pin;
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}
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bool AP_RangeFinder_HC_SR04::check_echo_pin()
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{
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return pwm_source.set_pin(params.pin, "HC_SR04");
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}
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/*
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detect if an HC_SR04 rangefinder is connected. The only thing we
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can do is check if the pin number is valid. If it is, then assume
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that the device is connected
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*/
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bool AP_RangeFinder_HC_SR04::detect(AP_RangeFinder_Params &_params)
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{
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if (_params.pin == -1) {
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return false;
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}
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if (_params.stop_pin == -1) {
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return false;
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}
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return true;
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}
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/*
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update distance_cm
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*/
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void AP_RangeFinder_HC_SR04::update(void)
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{
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// check if pin has changed and configure interrupt handlers if required:
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if (!check_pins()) {
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// disabled (either by configuration or failure to attach interrupt)
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state.distance_cm = 0.0f;
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return;
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}
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const uint32_t value_us = pwm_source.get_pwm_us();
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const uint32_t now = AP_HAL::millis();
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if (value_us == 0) {
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// no reading; check for timeout:
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if (now - last_reading_ms > 1000) {
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// no reading for a second - something is broken
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state.distance_cm = 0.0f;
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}
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} else {
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// gcs().send_text(MAV_SEVERITY_WARNING, "Pong!");
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// a new reading - convert time to distance
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state.distance_cm = value_us * (1.0/58.0f); // 58 is from datasheet, mult for performance
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// glitch remover: measurement is greater than .5m from last.
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// the SR-04 seeems to suffer from single-measurement glitches
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// which can be removed by a simple filter.
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if (labs(state.distance_cm - last_distance_cm) > 50) {
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// if greater for 5 readings then pass it as new height,
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// otherwise use last reading
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if (glitch_count++ > 4) {
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last_distance_cm = state.distance_cm;
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} else {
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state.distance_cm = last_distance_cm;
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}
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} else {
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// is not greater 0.5m, pass on and reset glitch counter
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last_distance_cm = state.distance_cm;
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glitch_count = 0;
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}
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last_reading_ms = now;
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}
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// update range_valid state based on distance measured
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update_status();
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// consider sending new ping
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if (now - last_ping_ms > 67) { // read ~@15Hz - recommended 60ms delay from datasheet
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last_ping_ms = now;
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// gcs().send_text(MAV_SEVERITY_INFO, "Ping!");
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// raise stop pin for n-microseconds
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hal.gpio->pinMode(trigger_pin, HAL_GPIO_OUTPUT);
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hal.gpio->write(trigger_pin, 1);
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hal.scheduler->delay_microseconds(10);
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hal.gpio->write(trigger_pin, 0);
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}
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}
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