mirror of https://github.com/ArduPilot/ardupilot
222 lines
6.2 KiB
C++
222 lines
6.2 KiB
C++
// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: t -*-
|
|
//
|
|
// DIYDrones Custom Mediatek GPS driver for ArduPilot and ArduPilotMega.
|
|
// Code by Michael Smith, Jordi Munoz and Jose Julio, DIYDrones.com
|
|
//
|
|
// This library is free software; you can redistribute it and / or
|
|
// modify it under the terms of the GNU Lesser General Public
|
|
// License as published by the Free Software Foundation; either
|
|
// version 2.1 of the License, or (at your option) any later version.
|
|
//
|
|
// GPS configuration : Custom protocol per "DIYDrones Custom Binary Sentence Specification V1.1"
|
|
//
|
|
|
|
#include "AP_GPS_MTK.h"
|
|
#include <stdint.h>
|
|
|
|
// Constructors ////////////////////////////////////////////////////////////////
|
|
AP_GPS_MTK::AP_GPS_MTK(Stream *s) : GPS(s)
|
|
{
|
|
}
|
|
|
|
// Public Methods //////////////////////////////////////////////////////////////
|
|
void
|
|
AP_GPS_MTK::init(enum GPS_Engine_Setting nav_setting)
|
|
{
|
|
_port->flush();
|
|
// initialize serial port for binary protocol use
|
|
// XXX should assume binary, let GPS_AUTO handle dynamic config?
|
|
_port->print(MTK_SET_BINARY);
|
|
|
|
// set 5Hz update rate
|
|
_port->print(MTK_OUTPUT_5HZ);
|
|
|
|
// set SBAS on
|
|
_port->print(SBAS_ON);
|
|
|
|
// set WAAS on
|
|
_port->print(WAAS_ON);
|
|
|
|
// Set Nav Threshold to 0 m/s
|
|
_port->print(MTK_NAVTHRES_OFF);
|
|
|
|
// set initial epoch code
|
|
_epoch = TIME_OF_DAY;
|
|
|
|
idleTimeout = 1200;
|
|
}
|
|
|
|
// Process bytes available from the stream
|
|
//
|
|
// The stream is assumed to contain only our custom message. If it
|
|
// contains other messages, and those messages contain the preamble bytes,
|
|
// it is possible for this code to become de-synchronised. Without
|
|
// buffering the entire message and re-processing it from the top,
|
|
// this is unavoidable.
|
|
//
|
|
// The lack of a standard header length field makes it impossible to skip
|
|
// unrecognised messages.
|
|
//
|
|
bool
|
|
AP_GPS_MTK::read(void)
|
|
{
|
|
uint8_t data;
|
|
int16_t numc;
|
|
bool parsed = false;
|
|
|
|
numc = _port->available();
|
|
for (int16_t i = 0; i < numc; i++) { // Process bytes received
|
|
|
|
// read the next byte
|
|
data = _port->read();
|
|
|
|
restart:
|
|
switch(_step) {
|
|
|
|
// Message preamble, class, ID detection
|
|
//
|
|
// If we fail to match any of the expected bytes, we
|
|
// reset the state machine and re-consider the failed
|
|
// byte as the first byte of the preamble. This
|
|
// improves our chances of recovering from a mismatch
|
|
// and makes it less likely that we will be fooled by
|
|
// the preamble appearing as data in some other message.
|
|
//
|
|
case 0:
|
|
if(PREAMBLE1 == data)
|
|
_step++;
|
|
break;
|
|
case 1:
|
|
if (PREAMBLE2 == data) {
|
|
_step++;
|
|
break;
|
|
}
|
|
_step = 0;
|
|
goto restart;
|
|
case 2:
|
|
if (MESSAGE_CLASS == data) {
|
|
_step++;
|
|
_ck_b = _ck_a = data; // reset the checksum accumulators
|
|
} else {
|
|
_step = 0; // reset and wait for a message of the right class
|
|
goto restart;
|
|
}
|
|
break;
|
|
case 3:
|
|
if (MESSAGE_ID == data) {
|
|
_step++;
|
|
_ck_b += (_ck_a += data);
|
|
_payload_counter = 0;
|
|
} else {
|
|
_step = 0;
|
|
goto restart;
|
|
}
|
|
break;
|
|
|
|
// Receive message data
|
|
//
|
|
case 4:
|
|
_buffer.bytes[_payload_counter++] = data;
|
|
_ck_b += (_ck_a += data);
|
|
if (_payload_counter == sizeof(_buffer))
|
|
_step++;
|
|
break;
|
|
|
|
// Checksum and message processing
|
|
//
|
|
case 5:
|
|
_step++;
|
|
if (_ck_a != data) {
|
|
_error("GPS_MTK: checksum error\n");
|
|
_step = 0;
|
|
}
|
|
break;
|
|
case 6:
|
|
_step = 0;
|
|
if (_ck_b != data) {
|
|
_error("GPS_MTK: checksum error\n");
|
|
break;
|
|
}
|
|
|
|
fix = _buffer.msg.fix_type == FIX_3D;
|
|
latitude = _swapl(&_buffer.msg.latitude) * 10;
|
|
longitude = _swapl(&_buffer.msg.longitude) * 10;
|
|
altitude = _swapl(&_buffer.msg.altitude);
|
|
ground_speed = _swapl(&_buffer.msg.ground_speed);
|
|
ground_course = _swapl(&_buffer.msg.ground_course) / 10000;
|
|
num_sats = _buffer.msg.satellites;
|
|
|
|
// time from gps is UTC, but convert here to msToD
|
|
int32_t time_utc = _swapl(&_buffer.msg.utc_time);
|
|
int32_t temp = (time_utc/10000000);
|
|
time_utc -= temp*10000000;
|
|
time = temp * 3600000;
|
|
temp = (time_utc/100000);
|
|
time_utc -= temp*100000;
|
|
time += temp * 60000 + time_utc;
|
|
|
|
parsed = true;
|
|
}
|
|
}
|
|
return parsed;
|
|
}
|
|
|
|
/*
|
|
detect a MTK GPS
|
|
*/
|
|
bool
|
|
AP_GPS_MTK::_detect(uint8_t data)
|
|
{
|
|
static uint8_t payload_counter;
|
|
static uint8_t step;
|
|
static uint8_t ck_a, ck_b;
|
|
|
|
switch(step) {
|
|
case 1:
|
|
if (PREAMBLE2 == data) {
|
|
step++;
|
|
break;
|
|
}
|
|
step = 0;
|
|
case 0:
|
|
ck_b = ck_a = payload_counter = 0;
|
|
if(PREAMBLE1 == data)
|
|
step++;
|
|
break;
|
|
case 2:
|
|
if (MESSAGE_CLASS == data) {
|
|
step++;
|
|
ck_b = ck_a = data;
|
|
} else {
|
|
step = 0;
|
|
}
|
|
break;
|
|
case 3:
|
|
if (MESSAGE_ID == data) {
|
|
step++;
|
|
ck_b += (ck_a += data);
|
|
payload_counter = 0;
|
|
} else {
|
|
step = 0;
|
|
}
|
|
break;
|
|
case 4:
|
|
ck_b += (ck_a += data);
|
|
if (++payload_counter == sizeof(struct diyd_mtk_msg))
|
|
step++;
|
|
break;
|
|
case 5:
|
|
step++;
|
|
if (ck_a != data) {
|
|
step = 0;
|
|
}
|
|
break;
|
|
case 6:
|
|
step = 0;
|
|
if (ck_b == data) {
|
|
return true;
|
|
}
|
|
}
|
|
return false;
|
|
}
|