Line data    Source code

       1             : /*
       2             :    This program is free software: you can redistribute it and/or modify
       3             :    it under the terms of the GNU General Public License as published by
       4             :    the Free Software Foundation, either version 3 of the License, or
       5             :    (at your option) any later version.
       6             : 
       7             :    This program is distributed in the hope that it will be useful,
       8             :    but WITHOUT ANY WARRANTY; without even the implied warranty of
       9             :    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      10             :    GNU General Public License for more details.
      11             : 
      12             :    You should have received a copy of the GNU General Public License
      13             :    along with this program.  If not, see <http://www.gnu.org/licenses/>.
      14             :  */
      15             : 
      16             : /*
      17             :  *   AP_RangeFinder_HC_SR04.cpp - rangefinder for HC_SR04 source
      18             :  *
      19             :  *   https://cdn.sparkfun.com/datasheets/Sensors/Proximity/HCSR04.pdf
      20             :  *
      21             :  *   There are two pins involved - one we attach an interrupt handler
      22             :  *   to and use for measuring the supplied interval which is
      23             :  *   proportional to distance.
      24             :  *
      25             :  *   The second pin we use for triggering the ultransonic pulse
      26             :  */
      27             : 
      28             : #include "AP_RangeFinder_HC_SR04.h"
      29             : 
      30             : #if AP_RANGEFINDER_HC_SR04_ENABLED
      31             : 
      32             : #include <AP_HAL/AP_HAL.h>
      33             : #include "AP_RangeFinder.h"
      34             : #include "AP_RangeFinder_Params.h"
      35             : 
      36             : #include <GCS_MAVLink/GCS.h>
      37             : 
      38             : extern const AP_HAL::HAL& hal;
      39             : 
      40           0 : AP_RangeFinder_HC_SR04::AP_RangeFinder_HC_SR04(RangeFinder::RangeFinder_State &_state, AP_RangeFinder_Params &_params) :
      41           0 :     AP_RangeFinder_Backend(_state, _params)
      42             : {
      43           0 :     set_status(RangeFinder::Status::NoData);
      44           0 : }
      45             : 
      46           0 : bool AP_RangeFinder_HC_SR04::check_pins()
      47             : {
      48           0 :     check_trigger_pin();
      49           0 :     return check_echo_pin() && trigger_pin > 0;
      50             : }
      51             : 
      52           0 : void AP_RangeFinder_HC_SR04::check_trigger_pin()
      53             : {
      54           0 :     if (params.stop_pin == trigger_pin) {
      55             :         // no change
      56           0 :         return;
      57             :     }
      58           0 :     trigger_pin = params.stop_pin;
      59             : }
      60             : 
      61           0 : bool AP_RangeFinder_HC_SR04::check_echo_pin()
      62             : {
      63           0 :     return pwm_source.set_pin(params.pin, "HC_SR04");
      64             : }
      65             : 
      66             : 
      67             : 
      68             : /*
      69             :    detect if an HC_SR04 rangefinder is connected. The only thing we
      70             :    can do is check if the pin number is valid. If it is, then assume
      71             :    that the device is connected
      72             : */
      73           0 : bool AP_RangeFinder_HC_SR04::detect(AP_RangeFinder_Params &_params)
      74             : {
      75           0 :     if (_params.pin == -1) {
      76           0 :         return false;
      77             :     }
      78           0 :     if (_params.stop_pin == -1) {
      79           0 :         return false;
      80             :     }
      81           0 :     return true;
      82             : }
      83             : 
      84             : 
      85             : /*
      86             :   update distance_cm
      87             :  */
      88           0 : void AP_RangeFinder_HC_SR04::update(void)
      89             : {
      90             :     // check if pin has changed and configure interrupt handlers if required:
      91           0 :     if (!check_pins()) {
      92             :         // disabled (either by configuration or failure to attach interrupt)
      93           0 :         state.distance_m = 0.0f;
      94           0 :         return;
      95             :     }
      96             : 
      97           0 :     const uint32_t value_us = pwm_source.get_pwm_us();
      98             : 
      99           0 :     const uint32_t now = AP_HAL::millis();
     100           0 :     if (value_us == 0) {
     101             :         // no reading; check for timeout:
     102           0 :         if (now - state.last_reading_ms > 1000) {
     103             :             // no reading for a second - something is broken
     104           0 :             state.distance_m = 0.0f;
     105             :         }
     106             :     } else {
     107             :         // GCS_SEND_TEXT(MAV_SEVERITY_WARNING, "Pong!");
     108             :         // a new reading - convert time to distance
     109           0 :         state.distance_m = (value_us * (1.0/58.0f)) * 0.01f;  // 58 is from datasheet, mult for performance
     110             : 
     111             :         // glitch remover: measurement is greater than .5m from last.
     112             :         // the SR-04 seeems to suffer from single-measurement glitches
     113             :         // which can be removed by a simple filter.
     114           0 :         if (fabsf(state.distance_m - last_distance_m) > 0.5f) {
     115             :             // if greater for 5 readings then pass it as new height,
     116             :             // otherwise use last reading
     117           0 :             if (glitch_count++ > 4) {
     118           0 :                  last_distance_m = state.distance_m;
     119             :             } else {
     120           0 :                  state.distance_m = last_distance_m;
     121             :             }
     122             :         } else {
     123             :             // is not greater 0.5m, pass on and reset glitch counter
     124           0 :             last_distance_m = state.distance_m;
     125           0 :             glitch_count = 0;
     126             :         }
     127             : 
     128           0 :         state.last_reading_ms = now;
     129             :     }
     130             : 
     131             :     // update range_valid state based on distance measured
     132           0 :     update_status();
     133             : 
     134             :     // consider sending new ping
     135           0 :     if (now - last_ping_ms > 67) { // read ~@15Hz - recommended 60ms delay from datasheet
     136           0 :         last_ping_ms = now;
     137             :         // GCS_SEND_TEXT(MAV_SEVERITY_INFO, "Ping!");
     138             :         // raise stop pin for n-microseconds
     139           0 :         hal.gpio->pinMode(trigger_pin, HAL_GPIO_OUTPUT);
     140           0 :         hal.gpio->write(trigger_pin, 1);
     141           0 :         hal.scheduler->delay_microseconds(10);
     142           0 :         hal.gpio->write(trigger_pin, 0);
     143             :     }
     144             : }
     145             : 
     146             : #endif  // AP_RANGEFINDER_HC_SR04_ENABLED