ardupilot/libraries/AP_RangeFinder/AP_RangeFinder_Benewake.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_RangeFinder_Benewake.h"
#include <AP_HAL/AP_HAL.h>
#include <AP_HAL/utility/sparse-endian.h>
#include <ctype.h>
extern const AP_HAL::HAL& hal;
#define BENEWAKE_FRAME_HEADER 0x59
#define BENEWAKE_FRAME_LENGTH 9
#define BENEWAKE_DIST_MAX_CM 32768
#define BENEWAKE_OUT_OF_RANGE_ADD_CM 100
// format of serial packets received from benewake lidar
//
// Data Bit Definition Description
// ------------------------------------------------
// byte 0 Frame header 0x59
// byte 1 Frame header 0x59
// byte 2 DIST_L Distance (in cm) low 8 bits
// byte 3 DIST_H Distance (in cm) high 8 bits
// byte 4 STRENGTH_L Strength low 8 bits
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// bute 4 (TF03) (Reserved)
// byte 5 STRENGTH_H Strength high 8 bits
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// bute 5 (TF03) (Reserved)
// byte 6 (TF02) SIG Reliability in 8 levels, 7 & 8 means reliable
// byte 6 (TFmini) Distance Mode 0x02 for short distance (mm), 0x07 for long distance (cm)
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// byte 6 (TF03) (Reserved)
// byte 7 (TF02 only) TIME Exposure time in two levels 0x03 and 0x06
// byte 8 Checksum Checksum byte, sum of bytes 0 to bytes 7
// distance returned in reading_m, signal_ok is set to true if sensor reports a strong signal
bool AP_RangeFinder_Benewake::get_reading(float &reading_m)
{
if (uart == nullptr) {
return false;
}
float sum_cm = 0;
uint16_t count = 0;
uint16_t count_out_of_range = 0;
// read any available lines from the lidar
int16_t nbytes = uart->available();
while (nbytes-- > 0) {
int16_t r = uart->read();
if (r < 0) {
continue;
}
uint8_t c = (uint8_t)r;
// if buffer is empty and this byte is 0x59, add to buffer
if (linebuf_len == 0) {
if (c == BENEWAKE_FRAME_HEADER) {
linebuf[linebuf_len++] = c;
}
} else if (linebuf_len == 1) {
// if buffer has 1 element and this byte is 0x59, add it to buffer
// if not clear the buffer
if (c == BENEWAKE_FRAME_HEADER) {
linebuf[linebuf_len++] = c;
} else {
linebuf_len = 0;
}
} else {
// add character to buffer
linebuf[linebuf_len++] = c;
// if buffer now has 9 items try to decode it
if (linebuf_len == BENEWAKE_FRAME_LENGTH) {
// calculate checksum
uint8_t checksum = 0;
for (uint8_t i=0; i<BENEWAKE_FRAME_LENGTH-1; i++) {
checksum += linebuf[i];
}
// if checksum matches extract contents
if (checksum == linebuf[BENEWAKE_FRAME_LENGTH-1]) {
// calculate distance
uint16_t dist = ((uint16_t)linebuf[3] << 8) | linebuf[2];
if (dist >= BENEWAKE_DIST_MAX_CM) {
// this reading is out of range
count_out_of_range++;
} else if (!has_signal_byte()) {
// no signal byte from TFmini so add distance to sum
sum_cm += dist;
count++;
} else {
// TF02 provides signal reliability (good = 7 or 8)
if (linebuf[6] >= 7) {
// add distance to sum
sum_cm += dist;
count++;
} else {
// this reading is out of range
count_out_of_range++;
}
}
}
// clear buffer
linebuf_len = 0;
}
}
}
if (count > 0) {
// return average distance of readings
reading_m = (sum_cm * 0.01f) / count;
return true;
}
if (count_out_of_range > 0) {
// if only out of range readings return larger of
// driver defined maximum range for the model and user defined max range + 1m
reading_m = MAX(model_dist_max_cm(), max_distance_cm() + BENEWAKE_OUT_OF_RANGE_ADD_CM) * 0.01f;
return true;
}
// no readings so return false
return false;
}