ardupilot/libraries/AP_WindVane/AP_WindVane_NMEA.cpp

211 lines
6.1 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_WindVane_NMEA.h"
#include <AP_SerialManager/AP_SerialManager.h>
/*
NMEA wind vane library, tested with Calypso Wired sensor,
should also work with other NMEA wind sensors using the MWV message,
heavily based on RangeFinder NMEA library
*/
// constructor
AP_WindVane_NMEA::AP_WindVane_NMEA(AP_WindVane &frontend) :
AP_WindVane_Backend(frontend)
{
}
// init - performs any required initialization for this instance
void AP_WindVane_NMEA::init(const AP_SerialManager& serial_manager)
{
uart = serial_manager.find_serial(AP_SerialManager::SerialProtocol_WindVane, 0);
if (uart != nullptr) {
uart->begin(serial_manager.find_baudrate(AP_SerialManager::SerialProtocol_WindVane, 0));
}
}
void AP_WindVane_NMEA::update_direction()
{
// Only call update from here if it has not been called already by update speed
if (_frontend._speed_sensor_type.get() != _frontend.Speed_type::WINDSPEED_NMEA) {
update();
}
}
void AP_WindVane_NMEA::update_speed()
{
update();
}
void AP_WindVane_NMEA::update()
{
if (uart == nullptr) {
return;
}
// read any available lines from the windvane
int16_t nbytes = uart->available();
while (nbytes-- > 0) {
char c = uart->read();
if (decode(c)) {
// user may not have NMEA selected for both speed and direction
if (_frontend._direction_type.get() == _frontend.WindVaneType::WINDVANE_NMEA) {
direction_update_frontend(wrap_PI(radians(_wind_dir_deg + _frontend._dir_analog_bearing_offset.get()) + AP::ahrs().yaw));
}
if (_frontend._speed_sensor_type.get() == _frontend.Speed_type::WINDSPEED_NMEA) {
speed_update_frontend(_speed_ms);
}
}
}
}
// add a single character to the buffer and attempt to decode
// returns true if a complete sentence was successfully decoded
bool AP_WindVane_NMEA::decode(char c)
{
switch (c) {
case ',':
// end of a term, add to checksum
_checksum ^= c;
FALLTHROUGH;
case '\r':
case '\n':
case '*':
{
// null terminate and decode latest term
_term[_term_offset] = 0;
bool valid_sentence = decode_latest_term();
// move onto next term
_term_number++;
_term_offset = 0;
_term_is_checksum = (c == '*');
return valid_sentence;
}
case '$': // sentence begin
_sentence_valid = false;
_term_number = 0;
_term_offset = 0;
_checksum = 0;
_term_is_checksum = false;
_wind_dir_deg = -1.0f;
_speed_ms = -1.0f;
return false;
}
// ordinary characters are added to term
if (_term_offset < sizeof(_term) - 1) {
_term[_term_offset++] = c;
}
if (!_term_is_checksum) {
_checksum ^= c;
}
return false;
}
// decode the most recently consumed term
// returns true if new sentence has just passed checksum test and is validated
bool AP_WindVane_NMEA::decode_latest_term()
{
// handle the last term in a message
if (_term_is_checksum) {
uint8_t checksum = 16 * char_to_hex(_term[0]) + char_to_hex(_term[1]);
return ((checksum == _checksum) && _sentence_valid);
}
// the first term determines the sentence type
if (_term_number == 0) {
// the first two letters of the NMEA term are the talker ID.
// we accept any two characters here.
if (_term[0] < 'A' || _term[0] > 'Z' ||
_term[1] < 'A' || _term[1] > 'Z') {
// unknown ID (we are actually expecting II)
return false;
}
const char *term_type = &_term[2];
if (strcmp(term_type, "MWV") == 0) {
// we found the sentence type for wind
_sentence_valid = true;
}
return false;
}
// if this is not the sentence we want then wait for another
if (!_sentence_valid) {
return false;
}
switch (_term_number) {
case 1:
_wind_dir_deg = strtof(_term, NULL);
// check for sensible value
if (is_negative(_wind_dir_deg) || _wind_dir_deg > 360.0f) {
_sentence_valid = false;
}
break;
case 2:
// we are expecting R for relative wind
// (could be T for true wind, maybe add in the future...)
if (_term[0] != 'R') {
_sentence_valid = false;
}
break;
case 3:
_speed_ms = strtof(_term, NULL);
break;
case 4:
if (_term[0] == 'K') {
// convert from km/h to m/s
_speed_ms *= KM_PER_HOUR_TO_M_PER_SEC;
} else if (_term[0] == 'N') {
// convert from Knots to m/s
_speed_ms *= KNOTS_TO_M_PER_SEC;
}
// could also be M for m/s, but we want that anyway so nothing to do
// check for sensible value
if (is_negative(_speed_ms) || _speed_ms > 100.0f) {
_sentence_valid = false;
}
break;
case 5:
// expecting A for data valid
if (_term[0] != 'A') {
_sentence_valid = false;
}
break;
}
return false;
}
// return the numeric value of an ascii hex character
int16_t AP_WindVane_NMEA::char_to_hex(char a)
{
if (a >= 'A' && a <= 'F')
return a - 'A' + 10;
else if (a >= 'a' && a <= 'f')
return a - 'a' + 10;
else
return a - '0';
}