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ardupilot/libraries/AP_GPS/AP_GPS_UBLOX.cpp

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// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: t -*-
//
// u-blox UBX 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.
//
#include <stdint.h>
#include <AP_HAL.h>
#define UBLOX_DEBUGGING 0
#if UBLOX_DEBUGGING
# define Debug(fmt, args ...) do {Serial.printf("%s:%d: " fmt "\n", __FUNCTION__, __LINE__, ## args); delay(0); } while(0)
#else
# define Debug(fmt, args ...)
#endif
#include "AP_GPS_UBLOX.h"
extern const AP_HAL::HAL& hal;
const prog_char AP_GPS_UBLOX::_ublox_set_binary[] PROGMEM = UBLOX_SET_BINARY;
const uint8_t AP_GPS_UBLOX::_ublox_set_binary_size = sizeof(AP_GPS_UBLOX::_ublox_set_binary);
// Public Methods //////////////////////////////////////////////////////////////
void
AP_GPS_UBLOX::init(AP_HAL::UARTDriver *s, enum GPS_Engine_Setting nav_setting)
{
_port = s;
// XXX it might make sense to send some CFG_MSG,CFG_NMEA messages to get the
// right reporting configuration.
Debug("uBlox nav_setting=%u\n", nav_setting);
_port->flush();
_epoch = TIME_OF_WEEK;
idleTimeout = 1200;
// configure the GPS for the messages we want
_configure_gps();
_nav_setting = nav_setting;
}
// Process bytes available from the stream
//
// The stream is assumed to contain only messages we recognise. If it
// contains other messages, and those messages contain the preamble
// bytes, it is possible for this code to fail to synchronise to the
// stream immediately. Without buffering the entire message and
// re-processing it from the top, this is unavoidable. The parser
// attempts to avoid this when possible.
//
bool
AP_GPS_UBLOX::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();
switch(_step) {
// Message preamble 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 1:
if (PREAMBLE2 == data) {
_step++;
break;
}
_step = 0;
Debug("reset %u", __LINE__);
// FALLTHROUGH
case 0:
if(PREAMBLE1 == data)
_step++;
break;
// Message header processing
//
// We sniff the class and message ID to decide whether we
// are going to gather the message bytes or just discard
// them.
//
// We always collect the length so that we can avoid being
// fooled by preamble bytes in messages.
//
case 2:
_step++;
_class = data;
_ck_b = _ck_a = data; // reset the checksum accumulators
break;
case 3:
_step++;
_ck_b += (_ck_a += data); // checksum byte
_msg_id = data;
break;
case 4:
_step++;
_ck_b += (_ck_a += data); // checksum byte
_payload_length = data; // payload length low byte
break;
case 5:
_step++;
_ck_b += (_ck_a += data); // checksum byte
_payload_length += (uint16_t)(data<<8);
if (_payload_length > 512) {
Debug("large payload %u", (unsigned)_payload_length);
// assume very large payloads are line noise
_payload_length = 0;
_step = 0;
}
_payload_counter = 0; // prepare to receive payload
break;
// Receive message data
//
case 6:
_ck_b += (_ck_a += data); // checksum byte
if (_payload_counter < sizeof(_buffer)) {
_buffer.bytes[_payload_counter] = data;
}
if (++_payload_counter == _payload_length)
_step++;
break;
// Checksum and message processing
//
case 7:
_step++;
if (_ck_a != data) {
Debug("bad cka %x should be %x", data, _ck_a);
_step = 0; // bad checksum
}
break;
case 8:
_step = 0;
if (_ck_b != data) {
Debug("bad ckb %x should be %x", data, _ck_b);
break; // bad checksum
}
if (_parse_gps()) {
parsed = true;
}
}
}
return parsed;
}
// Private Methods /////////////////////////////////////////////////////////////
bool
AP_GPS_UBLOX::_parse_gps(void)
{
if (_class == CLASS_ACK) {
Debug("ACK %u", (unsigned)_msg_id);
return false;
}
if (_class == CLASS_CFG && _msg_id == MSG_CFG_NAV_SETTINGS) {
Debug("Got engine settings %u\n", (unsigned)_buffer.nav_settings.dynModel);
if (_nav_setting != GPS_ENGINE_NONE &&
_buffer.nav_settings.dynModel != _nav_setting) {
// we've received the current nav settings, change the engine
// settings and send them back
Debug("Changing engine setting from %u to %u\n",
(unsigned)_buffer.nav_settings.dynModel, (unsigned)_nav_setting);
_buffer.nav_settings.dynModel = _nav_setting;
_send_message(CLASS_CFG, MSG_CFG_NAV_SETTINGS,
&_buffer.nav_settings,
sizeof(_buffer.nav_settings));
}
return false;
}
if (_class != CLASS_NAV) {
Debug("Unexpected message 0x%02x 0x%02x", (unsigned)_class, (unsigned)_msg_id);
if (++_disable_counter == 0) {
// disable future sends of this message id, but
// only do this every 256 messages, as some
// message types can't be disabled and we don't
// want to get into an ack war
Debug("Disabling message 0x%02x 0x%02x", (unsigned)_class, (unsigned)_msg_id);
_configure_message_rate(_class, _msg_id, 0);
}
return false;
}
switch (_msg_id) {
case MSG_POSLLH:
Debug("MSG_POSLLH next_fix=%u", next_fix);
time = _buffer.posllh.time;
longitude = _buffer.posllh.longitude;
latitude = _buffer.posllh.latitude;
altitude = _buffer.posllh.altitude_msl / 10;
fix = next_fix;
_new_position = true;
break;
case MSG_STATUS:
Debug("MSG_STATUS fix_status=%u fix_type=%u",
_buffer.status.fix_status,
_buffer.status.fix_type);
next_fix = (_buffer.status.fix_status & NAV_STATUS_FIX_VALID) && (_buffer.status.fix_type == FIX_3D);
if (!next_fix) {
fix = false;
}
break;
case MSG_SOL:
Debug("MSG_SOL fix_status=%u fix_type=%u",
_buffer.solution.fix_status,
_buffer.solution.fix_type);
next_fix = (_buffer.solution.fix_status & NAV_STATUS_FIX_VALID) && (_buffer.solution.fix_type == FIX_3D);
if (!next_fix) {
fix = false;
}
num_sats = _buffer.solution.satellites;
hdop = _buffer.solution.position_DOP;
break;
case MSG_VELNED:
Debug("MSG_VELNED");
speed_3d = _buffer.velned.speed_3d; // cm/s
ground_speed = _buffer.velned.speed_2d; // cm/s
ground_course = _buffer.velned.heading_2d / 1000; // Heading 2D deg * 100000 rescaled to deg * 100
_have_raw_velocity = true;
_vel_north = _buffer.velned.ned_north;
_vel_east = _buffer.velned.ned_east;
_vel_down = _buffer.velned.ned_down;
_new_speed = true;
break;
default:
Debug("Unexpected NAV message 0x%02x", (unsigned)_msg_id);
if (++_disable_counter == 0) {
Debug("Disabling NAV message 0x%02x", (unsigned)_msg_id);
_configure_message_rate(CLASS_NAV, _msg_id, 0);
}
return false;
}
// we only return true when we get new position and speed data
// this ensures we don't use stale data
if (_new_position && _new_speed) {
_new_speed = _new_position = false;
_fix_count++;
if (_fix_count == 100) {
// ask for nav settings every 20 seconds
Debug("Asking for engine setting\n");
_send_message(CLASS_CFG, MSG_CFG_NAV_SETTINGS, NULL, 0);
}
return true;
}
return false;
}
// UBlox auto configuration
/*
* update checksum for a set of bytes
*/
void
AP_GPS_UBLOX::_update_checksum(uint8_t *data, uint8_t len, uint8_t &ck_a, uint8_t &ck_b)
{
while (len--) {
ck_a += *data;
ck_b += ck_a;
data++;
}
}
/*
* send a ublox message
*/
void
AP_GPS_UBLOX::_send_message(uint8_t msg_class, uint8_t msg_id, void *msg, uint8_t size)
{
struct ubx_header header;
uint8_t ck_a=0, ck_b=0;
header.preamble1 = PREAMBLE1;
header.preamble2 = PREAMBLE2;
header.msg_class = msg_class;
header.msg_id = msg_id;
header.length = size;
_update_checksum((uint8_t *)&header.msg_class, sizeof(header)-2, ck_a, ck_b);
_update_checksum((uint8_t *)msg, size, ck_a, ck_b);
_port->write((const uint8_t *)&header, sizeof(header));
_port->write((const uint8_t *)msg, size);
_port->write((const uint8_t *)&ck_a, 1);
_port->write((const uint8_t *)&ck_b, 1);
}
/*
* configure a UBlox GPS for the given message rate for a specific
* message class and msg_id
*/
void
AP_GPS_UBLOX::_configure_message_rate(uint8_t msg_class, uint8_t msg_id, uint8_t rate)
{
struct ubx_cfg_msg_rate msg;
msg.msg_class = msg_class;
msg.msg_id = msg_id;
msg.rate = rate;
_send_message(CLASS_CFG, MSG_CFG_SET_RATE, &msg, sizeof(msg));
}
/*
* configure a UBlox GPS for the given message rate
*/
void
AP_GPS_UBLOX::_configure_gps(void)
{
struct ubx_cfg_nav_rate msg;
const unsigned baudrates[4] = {9600U, 19200U, 38400U, 57600U};
// the GPS may be setup for a different baud rate. This ensures
// it gets configured correctly
for (uint8_t i=0; i<4; i++) {
_port->begin(baudrates[i]);
_write_progstr_block(_port, _ublox_set_binary, _ublox_set_binary_size);
while (_port->tx_pending()) {
hal.scheduler->delay(1);
}
}
_port->begin(38400U);
// ask for navigation solutions every 200ms
msg.measure_rate_ms = 200;
msg.nav_rate = 1;
msg.timeref = 0; // UTC time
_send_message(CLASS_CFG, MSG_CFG_RATE, &msg, sizeof(msg));
// ask for the messages we parse to be sent on every navigation solution
_configure_message_rate(CLASS_NAV, MSG_POSLLH, 1);
_configure_message_rate(CLASS_NAV, MSG_STATUS, 1);
_configure_message_rate(CLASS_NAV, MSG_SOL, 1);
_configure_message_rate(CLASS_NAV, MSG_VELNED, 1);
// ask for the current navigation settings
Debug("Asking for engine setting\n");
_send_message(CLASS_CFG, MSG_CFG_NAV_SETTINGS, NULL, 0);
}
/*
detect a Ublox GPS. Adds one byte, and returns true if the stream
matches a UBlox
*/
bool
AP_GPS_UBLOX::_detect(uint8_t data)
{
static uint8_t payload_length, 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:
if (PREAMBLE1 == data)
step++;
break;
case 2:
step++;
ck_b = ck_a = data;
break;
case 3:
step++;
ck_b += (ck_a += data);
break;
case 4:
step++;
ck_b += (ck_a += data);
payload_length = data;
break;
case 5:
step++;
ck_b += (ck_a += data);
payload_counter = 0;
break;
case 6:
ck_b += (ck_a += data);
if (++payload_counter == payload_length)
step++;
break;
case 7:
step++;
if (ck_a != data) {
step = 0;
}
break;
case 8:
step = 0;
if (ck_b == data) {
// a valid UBlox packet
return true;
}
}
return false;
}
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