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ardupilot/libraries/AP_GPS/AP_GPS_ERB.cpp

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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/>.
*/
//
// Emlid Reach Binary (ERB) GPS driver for ArduPilot.
// ERB protocol: http://files.emlid.com/ERB.pdf
#include "AP_GPS.h"
#include "AP_GPS_ERB.h"
#define ERB_DEBUGGING 0
#define STAT_FIX_VALID 0x01
extern const AP_HAL::HAL& hal;
#if ERB_DEBUGGING
# define Debug(fmt, args ...) do {hal.console->printf("%s:%d: " fmt "\n", __FUNCTION__, __LINE__, ## args); hal.scheduler->delay(1); } while(0)
#else
# define Debug(fmt, args ...)
#endif
// 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_ERB::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();
reset:
switch(_step) {
// Message preamble detection
//
case 1:
if (PREAMBLE2 == data) {
_step++;
break;
}
_step = 0;
Debug("reset %u", __LINE__);
FALLTHROUGH;
case 0:
if(PREAMBLE1 == data)
_step++;
break;
// Message header processing
//
case 2:
_step++;
_msg_id = data;
_ck_b = _ck_a = data; // reset the checksum accumulators
break;
case 3:
_step++;
_ck_b += (_ck_a += data); // checksum byte
_payload_length = data; // payload length low byte
break;
case 4:
_step++;
_ck_b += (_ck_a += data); // checksum byte
_payload_length += (uint16_t)(data<<8);
_payload_counter = 0; // prepare to receive payload
break;
// Receive message data
//
case 5:
_ck_b += (_ck_a += data); // checksum byte
if (_payload_counter < sizeof(_buffer)) {
_buffer[_payload_counter] = data;
}
if (++_payload_counter == _payload_length)
_step++;
break;
// Checksum and message processing
//
case 6:
_step++;
if (_ck_a != data) {
Debug("bad cka %x should be %x", data, _ck_a);
_step = 0;
goto reset;
}
break;
case 7:
_step = 0;
if (_ck_b != data) {
Debug("bad ckb %x should be %x", data, _ck_b);
break; // bad checksum
}
if (_parse_gps()) {
parsed = true;
}
break;
}
}
return parsed;
}
bool
AP_GPS_ERB::_parse_gps(void)
{
switch (_msg_id) {
case MSG_VER:
Debug("Version of ERB protocol %u.%u.%u",
_buffer.ver.ver_high,
_buffer.ver.ver_medium,
_buffer.ver.ver_low);
break;
case MSG_POS:
Debug("Message POS");
_last_pos_time = _buffer.pos.time;
state.location.lng = (int32_t)(_buffer.pos.longitude * (double)1e7);
state.location.lat = (int32_t)(_buffer.pos.latitude * (double)1e7);
state.location.alt = (int32_t)(_buffer.pos.altitude_msl * 100);
state.status = next_fix;
_new_position = true;
state.horizontal_accuracy = _buffer.pos.horizontal_accuracy * 1.0e-3f;
state.vertical_accuracy = _buffer.pos.vertical_accuracy * 1.0e-3f;
state.have_horizontal_accuracy = true;
state.have_vertical_accuracy = true;
break;
case MSG_STAT:
Debug("Message STAT fix_status=%u fix_type=%u",
_buffer.stat.fix_status,
_buffer.stat.fix_type);
if (_buffer.stat.fix_status & STAT_FIX_VALID) {
if (_buffer.stat.fix_type == AP_GPS_ERB::FIX_FIX) {
next_fix = AP_GPS::GPS_OK_FIX_3D_RTK_FIXED;
} else if (_buffer.stat.fix_type == AP_GPS_ERB::FIX_FLOAT) {
next_fix = AP_GPS::GPS_OK_FIX_3D_RTK_FLOAT;
} else if (_buffer.stat.fix_type == AP_GPS_ERB::FIX_SINGLE) {
next_fix = AP_GPS::GPS_OK_FIX_3D;
} else {
next_fix = AP_GPS::NO_FIX;
state.status = AP_GPS::NO_FIX;
}
} else {
next_fix = AP_GPS::NO_FIX;
state.status = AP_GPS::NO_FIX;
}
state.num_sats = _buffer.stat.satellites;
if (next_fix >= AP_GPS::GPS_OK_FIX_3D) {
// use the uart receive time to make packet timestamps more accurate
set_uart_timestamp(_payload_length + sizeof(erb_header) + 2);
state.last_gps_time_ms = AP_HAL::millis();
state.time_week_ms = _buffer.stat.time;
state.time_week = _buffer.stat.week;
}
break;
case MSG_DOPS:
Debug("Message DOPS");
state.hdop = _buffer.dops.hDOP;
state.vdop = _buffer.dops.vDOP;
break;
case MSG_VEL:
Debug("Message VEL");
_last_vel_time = _buffer.vel.time;
state.ground_speed = _buffer.vel.speed_2d * 0.01f; // m/s
// Heading 2D deg * 100000 rescaled to deg * 100
state.ground_course = wrap_360(_buffer.vel.heading_2d * 1.0e-5f);
state.have_vertical_velocity = true;
state.velocity.x = _buffer.vel.vel_north * 0.01f;
state.velocity.y = _buffer.vel.vel_east * 0.01f;
state.velocity.z = _buffer.vel.vel_down * 0.01f;
state.have_speed_accuracy = true;
state.speed_accuracy = _buffer.vel.speed_accuracy * 0.01f;
_new_speed = true;
break;
case MSG_RTK:
Debug("Message RTK");
state.rtk_baseline_coords_type = RTK_BASELINE_COORDINATE_SYSTEM_NED;
state.rtk_num_sats = _buffer.rtk.base_num_sats;
if (_buffer.rtk.age_cs == 0xFFFF) {
state.rtk_age_ms = 0xFFFFFFFF;
} else {
state.rtk_age_ms = _buffer.rtk.age_cs * 10;
}
state.rtk_baseline_x_mm = _buffer.rtk.baseline_N_mm;
state.rtk_baseline_y_mm = _buffer.rtk.baseline_E_mm;
state.rtk_baseline_z_mm = _buffer.rtk.baseline_D_mm;
state.rtk_accuracy = _buffer.rtk.ar_ratio;
state.rtk_week_number = _buffer.rtk.base_week_number;
state.rtk_time_week_ms = _buffer.rtk.base_time_week_ms;
break;
default:
Debug("Unexpected message 0x%02x", (unsigned)_msg_id);
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 && _last_vel_time == _last_pos_time) {
_new_speed = _new_position = false;
_fix_count++;
return true;
}
return false;
}
/*
detect a ERB GPS. Adds one byte, and returns true if the stream
matches a ERB
*/
bool
AP_GPS_ERB::_detect(struct ERB_detect_state &state, uint8_t data)
{
reset:
switch (state.step) {
case 1:
if (PREAMBLE2 == data) {
state.step++;
break;
}
state.step = 0;
FALLTHROUGH;
case 0:
if (PREAMBLE1 == data)
state.step++;
break;
case 2:
state.step++;
state.ck_b = state.ck_a = data;
break;
case 3:
state.step++;
state.ck_b += (state.ck_a += data);
state.payload_length = data;
break;
case 4:
state.step++;
state.ck_b += (state.ck_a += data);
state.payload_counter = 0;
break;
case 5:
state.ck_b += (state.ck_a += data);
if (++state.payload_counter == state.payload_length)
state.step++;
break;
case 6:
state.step++;
if (state.ck_a != data) {
state.step = 0;
goto reset;
}
break;
case 7:
state.step = 0;
if (state.ck_b == data) {
return true;
} else {
goto reset;
}
}
return false;
}
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