mirror of https://github.com/ArduPilot/ardupilot
144 lines
4.3 KiB
C++
144 lines
4.3 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_config.h"
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#if AP_RANGEFINDER_JRE_SERIAL_ENABLED
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#include "AP_RangeFinder_JRE_Serial.h"
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#include <AP_Math/AP_Math.h>
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#define FRAME_HEADER_1 'R' // 0x52
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#define FRAME_HEADER_2_A 'A' // 0x41
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#define FRAME_HEADER_2_B 'B' // 0x42
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#define FRAME_HEADER_2_C 'C' // 0x43
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#define DIST_MAX_CM 5000
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#define OUT_OF_RANGE_ADD_CM 100
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void AP_RangeFinder_JRE_Serial::move_preamble_in_buffer(uint8_t search_start_pos)
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{
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uint8_t i;
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for (i=search_start_pos; i<data_buff_ofs; i++) {
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if (data_buff[i] == FRAME_HEADER_1) {
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break;
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}
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}
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if (i == 0) {
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return;
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}
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memmove(data_buff, &data_buff[i], data_buff_ofs-i);
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data_buff_ofs = data_buff_ofs - i;
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}
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bool AP_RangeFinder_JRE_Serial::get_reading(float &reading_m)
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{
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// uart instance check
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if (uart == nullptr) {
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return false; // not update
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}
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uint16_t valid_count = 0; // number of valid readings
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uint16_t invalid_count = 0; // number of invalid readings
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float sum = 0;
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// read a maximum of 8192 bytes per call to this function:
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uint16_t bytes_available = MIN(uart->available(), 8192U);
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while (bytes_available > 0) {
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// fill buffer
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const auto num_bytes_to_read = MIN(bytes_available, ARRAY_SIZE(data_buff) - data_buff_ofs);
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const auto num_bytes_read = uart->read(&data_buff[data_buff_ofs], num_bytes_to_read);
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if (num_bytes_read == 0) {
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break;
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}
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if (bytes_available < num_bytes_read) {
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// this is a bug in the uart call.
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break;
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}
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bytes_available -= num_bytes_read;
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data_buff_ofs += num_bytes_read;
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// move header frame header in buffer
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move_preamble_in_buffer(0);
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// ensure we have a packet type:
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if (data_buff_ofs < 2) {
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continue;
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}
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// determine packet length for incoming packet:
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uint8_t packet_length;
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switch (data_buff[1]) {
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case FRAME_HEADER_2_A:
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packet_length = 16;
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break;
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case FRAME_HEADER_2_B:
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packet_length = 32;
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break;
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case FRAME_HEADER_2_C:
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packet_length = 48;
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break;
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default:
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move_preamble_in_buffer(1);
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continue;
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}
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// check there are enough bytes for message type
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if (data_buff_ofs < packet_length) {
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continue;
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}
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// check the checksum
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const uint16_t crc = crc16_ccitt_r(data_buff, packet_length - 2, 0xffff, 0xffff);
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if (crc != ((data_buff[packet_length-1] << 8) | data_buff[packet_length-2])) {
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// CRC failure
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move_preamble_in_buffer(1);
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continue;
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}
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// check random bit to for magic value:
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if (data_buff[packet_length-3] & 0x02) { // NTRK
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invalid_count++;
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// discard entire packet:
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move_preamble_in_buffer(packet_length);
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continue;
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}
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// good message, extract rangefinder reading:
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reading_m = (data_buff[4] * 256 + data_buff[5]) * 0.01f;
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sum += reading_m;
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valid_count++;
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move_preamble_in_buffer(packet_length);
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}
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// return average of all valid readings
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if (valid_count > 0) {
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no_signal = false;
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reading_m = sum / valid_count;
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return true;
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}
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// all readings were invalid so return out-of-range-high value
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if (invalid_count > 0) {
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no_signal = true;
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reading_m = MIN(MAX(DIST_MAX_CM, max_distance_cm() + OUT_OF_RANGE_ADD_CM), UINT16_MAX) * 0.01f;
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return true;
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}
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return false;
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}
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#endif // AP_RANGEFINDER_JRE_SERIAL_ENABLED
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