ardupilot/libraries/AP_RangeFinder/AP_RangeFinder_LightWareSer...

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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_LightWareSerial.h"
#include <AP_HAL/AP_HAL.h>
#include <ctype.h>
extern const AP_HAL::HAL& hal;
#define LIGHTWARE_DIST_MAX_CM 10000
#define LIGHTWARE_OUT_OF_RANGE_ADD_CM 100
// read - return last value measured by sensor
bool AP_RangeFinder_LightWareSerial::get_reading(float &reading_m)
{
if (uart == nullptr) {
return false;
}
float sum = 0; // sum of all readings taken
uint16_t valid_count = 0; // number of valid readings
uint16_t invalid_count = 0; // number of invalid readings
// max distance the sensor can reliably measure - read from parameters
const int16_t distance_cm_max = max_distance_cm();
// read any available lines from the lidar
int16_t nbytes = uart->available();
while (nbytes-- > 0) {
char c = uart->read();
// use legacy protocol
if (protocol_state == ProtocolState::UNKNOWN || protocol_state == ProtocolState::LEGACY) {
if (c == '\r') {
linebuf[linebuf_len] = 0;
const float dist = strtof(linebuf, nullptr);
if (!is_negative(dist) && !is_lost_signal_distance(dist * 100, distance_cm_max)) {
sum += dist;
valid_count++;
// if still determining protocol update legacy valid count
if (protocol_state == ProtocolState::UNKNOWN) {
legacy_valid_count++;
}
} else {
invalid_count++;
}
linebuf_len = 0;
} else if (isdigit(c) || c == '.' || c == '-') {
linebuf[linebuf_len++] = c;
if (linebuf_len == sizeof(linebuf)) {
// too long, discard the line
linebuf_len = 0;
}
}
}
// use binary protocol
if (protocol_state == ProtocolState::UNKNOWN || protocol_state == ProtocolState::BINARY) {
bool msb_set = BIT_IS_SET(c, 7);
if (msb_set) {
// received the high byte
high_byte = c;
high_byte_received = true;
} else {
// received the low byte which should be second
if (high_byte_received) {
const int16_t dist = (high_byte & 0x7f) << 7 | (c & 0x7f);
if (dist >= 0 && !is_lost_signal_distance(dist, distance_cm_max)) {
sum += dist * 0.01f;
valid_count++;
// if still determining protocol update binary valid count
if (protocol_state == ProtocolState::UNKNOWN) {
binary_valid_count++;
}
} else {
invalid_count++;
}
}
high_byte_received = false;
}
}
}
// protocol set after 10 successful reads
if (protocol_state == ProtocolState::UNKNOWN) {
if (binary_valid_count > 10) {
protocol_state = ProtocolState::BINARY;
} else if (legacy_valid_count > 10) {
protocol_state = ProtocolState::LEGACY;
}
}
uint32_t now = AP_HAL::millis();
if (last_init_ms == 0 ||
(now - last_init_ms > 1000 &&
now - state.last_reading_ms > 1000)) {
// send enough serial transitions to trigger LW20 into serial
// mode. It starts in dual I2C/serial mode, and wants to see
// enough transitions to switch into serial mode.
uart->write("www\r\n");
last_init_ms = now;
} else {
uart->write('d');
}
// return average of all valid readings
if (valid_count > 0) {
reading_m = sum / valid_count;
no_signal = false;
return true;
}
// all readings were invalid so return out-of-range-high value
if (invalid_count > 0) {
reading_m = MIN(MAX(LIGHTWARE_DIST_MAX_CM, distance_cm_max + LIGHTWARE_OUT_OF_RANGE_ADD_CM), UINT16_MAX) * 0.01f;
no_signal = true;
return true;
}
// no readings so return false
return false;
}
// check to see if distance returned by the LiDAR is a known lost-signal distance flag
bool AP_RangeFinder_LightWareSerial::is_lost_signal_distance(int16_t distance_cm, int16_t distance_cm_max)
{
if (distance_cm < distance_cm_max + LIGHTWARE_OUT_OF_RANGE_ADD_CM) {
// in-range
return false;
}
const int16_t bad_distances[] { 13000, 16000, 23000, 25000 };
for (const auto bad_distance_cm : bad_distances) {
if (distance_cm == bad_distance_cm) {
return true;
}
}
return false;
}