ardupilot/libraries/AP_RangeFinder/AP_RangeFinder_Benewake.cpp

167 lines
6.4 KiB
C++

/*
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 "AP_RangeFinder_Benewake.h"
#include <AP_SerialManager/AP_SerialManager.h>
#include <ctype.h>
#include <AP_HAL/utility/sparse-endian.h>
extern const AP_HAL::HAL& hal;
#define BENEWAKE_FRAME_HEADER 0x59
#define BENEWAKE_FRAME_LENGTH 9
#define BENEWAKE_DIST_MAX_CM 32768
// 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
// byte 5 STRENGTH_H Strength high 8 bits
// 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)
// 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
/*
The constructor also initialises the rangefinder. Note that this
constructor is not called until detect() returns true, so we
already know that we should setup the rangefinder
*/
AP_RangeFinder_Benewake::AP_RangeFinder_Benewake(RangeFinder::RangeFinder_State &_state,
AP_SerialManager &serial_manager,
uint8_t serial_instance,
benewake_model_type model) :
AP_RangeFinder_Backend(_state),
model_type(model)
{
uart = serial_manager.find_serial(AP_SerialManager::SerialProtocol_Rangefinder, serial_instance);
if (uart != nullptr) {
uart->begin(serial_manager.find_baudrate(AP_SerialManager::SerialProtocol_Rangefinder, serial_instance));
}
}
/*
detect if a Benewake rangefinder is connected. We'll detect by
trying to take a reading on Serial. If we get a result the sensor is
there.
*/
bool AP_RangeFinder_Benewake::detect(AP_SerialManager &serial_manager, uint8_t serial_instance)
{
return serial_manager.find_serial(AP_SerialManager::SerialProtocol_Rangefinder, serial_instance) != nullptr;
}
// distance returned in reading_cm, signal_ok is set to true if sensor reports a strong signal
bool AP_RangeFinder_Benewake::get_reading(uint16_t &reading_cm, bool &signal_ok)
{
if (uart == nullptr) {
return false;
}
float sum_cm = 0;
uint16_t count = 0;
bool dist_reliable = false;
// read any available lines from the lidar
int16_t nbytes = uart->available();
while (nbytes-- > 0) {
char c = uart->read();
// 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;
dist_reliable = false;
}
} 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
uint16_t checksum = 0;
for (uint8_t i=0; i<BENEWAKE_FRAME_LENGTH-1; i++) {
checksum += linebuf[i];
}
// if checksum matches extract contents
if ((uint8_t)(checksum & 0xFF) == linebuf[BENEWAKE_FRAME_LENGTH-1]) {
// tell caller we are receiving packets
signal_ok = true;
// calculate distance and add to sum
uint16_t dist = ((uint16_t)linebuf[3] << 8) | linebuf[2];
if (dist < BENEWAKE_DIST_MAX_CM) {
// TFmini has short distance mode (mm)
if (model_type == BENEWAKE_TFmini) {
if (linebuf[6] == 0x02) {
dist *= 0.1f;
}
// no signal byte from TFmini
dist_reliable = true;
} else {
// TF02 provides signal reliability (good = 7 or 8)
dist_reliable = (linebuf[6] >= 7);
}
if (dist_reliable) {
sum_cm += dist;
count++;
}
}
}
// clear buffer
linebuf_len = 0;
dist_reliable = false;
}
}
}
if (count == 0) {
return false;
}
reading_cm = sum_cm / count;
return true;
}
/*
update the state of the sensor
*/
void AP_RangeFinder_Benewake::update(void)
{
bool signal_ok;
if (get_reading(state.distance_cm, signal_ok)) {
// update range_valid state based on distance measured
state.last_reading_ms = AP_HAL::millis();
if (signal_ok) {
update_status();
} else {
// if signal is weak set status to out-of-range
set_status(RangeFinder::RangeFinder_OutOfRangeHigh);
}
} else if (AP_HAL::millis() - state.last_reading_ms > 200) {
set_status(RangeFinder::RangeFinder_NoData);
}
}