mirror of https://github.com/ArduPilot/ardupilot
121 lines
4.1 KiB
C++
121 lines
4.1 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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#include "AP_RangeFinder_TeraRanger_Serial.h"
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#if AP_RANGEFINDER_TERARANGER_SERIAL_ENABLED
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#include <AP_HAL/AP_HAL.h>
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#include <AP_HAL/utility/sparse-endian.h>
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#include <AP_Math/AP_Math.h>
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#include <ctype.h>
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extern const AP_HAL::HAL& hal;
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#define FRAME_HEADER 0x54
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#define FRAME_LENGTH 5
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#define DIST_MAX_CM 3000
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#define OUT_OF_RANGE_ADD_CM 1000
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#define STATUS_MASK 0x1F
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#define DISTANCE_ERROR 0x0001
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// format of serial packets received from rangefinder
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//
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// Data Bit Definition Description
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// ------------------------------------------------
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// byte 0 Frame header 0x54
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// byte 1 DIST_H Distance (in mm) high 8 bits
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// byte 2 DIST_L Distance (in mm) low 8 bits
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// byte 3 STATUS Status,Strengh,OverTemp
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// byte 4 CRC8 packet CRC
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// distance returned in reading_m, set to true if sensor reports a good reading
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bool AP_RangeFinder_TeraRanger_Serial::get_reading(float &reading_m)
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{
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if (uart == nullptr) {
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return false;
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}
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float sum_mm = 0;
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uint16_t count = 0;
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uint16_t bad_read = 0;
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// read any available lines from the lidar
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int16_t nbytes = uart->available();
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while (nbytes-- > 0) {
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int16_t r = uart->read();
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if (r < 0) {
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continue;
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}
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uint8_t c = (uint8_t)r;
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// if buffer is empty and this byte is 0x57, add to buffer
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if (linebuf_len == 0) {
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if (c == FRAME_HEADER) {
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linebuf[linebuf_len++] = c;
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}
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// buffer is not empty, add byte to buffer
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} else {
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// add character to buffer
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linebuf[linebuf_len++] = c;
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// if buffer now has 5 items try to decode it
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if (linebuf_len == FRAME_LENGTH) {
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// calculate CRC8 (tbd)
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uint8_t crc = 0;
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crc =crc_crc8(linebuf,FRAME_LENGTH-1);
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// if crc matches, extract contents
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if (crc == linebuf[FRAME_LENGTH-1]) {
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// calculate distance
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uint16_t dist = ((uint16_t)linebuf[1] << 8) | linebuf[2];
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if (dist >= DIST_MAX_CM *10) {
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// this reading is out of range and a bad read
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bad_read++;
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} else {
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// check if reading is good, no errors, no overtemp, reading is not the special case of 1mm
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if ((STATUS_MASK & linebuf[3]) == 0 && (dist != DISTANCE_ERROR)) {
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// add distance to sum
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sum_mm += dist;
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count++;
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} else {
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// this reading is bad
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bad_read++;
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}
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}
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}
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// clear buffer
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linebuf_len = 0;
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}
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}
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}
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if (count > 0) {
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// return average distance of readings since last update
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reading_m = (sum_mm * 0.001f) / count;
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return true;
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}
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if (bad_read > 0) {
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// if a bad read has occurred this update overwrite return with larger of
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// driver defined maximum range for the model and user defined max range + 1m
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reading_m = MAX(DIST_MAX_CM, max_distance_cm() + OUT_OF_RANGE_ADD_CM) * 0.01f;
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return true;
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}
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// no readings so return false
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return false;
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}
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#endif // AP_RANGEFINDER_TERARANGER_SERIAL_ENABLED
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