mirror of https://github.com/ArduPilot/ardupilot
239 lines
7.9 KiB
C++
239 lines
7.9 KiB
C++
/* #################################################################################################################
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* LightTelemetry protocol (LTM)
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*
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* Ghettostation one way telemetry protocol for really low bitrates (2400 bauds).
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*
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* Protocol details: 3 different frames, little endian.
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* G Frame (GPS position) (2 Hz): 18BYTES
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* 0x24 0x54 0x47 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xC0
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* $ T G --------LAT-------- -------LON--------- SPD --------ALT-------- SAT/FIX CRC
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* A Frame (Attitude) (5 Hz): 10BYTES
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* 0x24 0x54 0x41 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xC0
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* $ T A --PITCH-- --ROLL--- -HEADING- CRC
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* S Frame (Sensors) (2 Hz): 11BYTES
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* 0x24 0x54 0x53 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xC0
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* $ T S VBAT(mV) Current(mA) RSSI AIRSPEED ARM/FS/FMOD CRC
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* ################################################################################################################# */
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#include "AP_LTM_Telem.h"
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#if AP_LTM_TELEM_ENABLED
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#include <AP_AHRS/AP_AHRS.h>
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#include <AP_GPS/AP_GPS.h>
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#include <AP_BattMonitor/AP_BattMonitor.h>
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#include <AP_Notify/AP_Notify.h>
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#include <AP_RSSI/AP_RSSI.h>
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#include <AP_SerialManager/AP_SerialManager.h>
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extern const AP_HAL::HAL& hal;
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// init - perform required initialisation
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void AP_LTM_Telem::init()
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{
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const AP_SerialManager &serial_manager = AP::serialmanager();
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// check for LTM_Port
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if ((_port = serial_manager.find_serial(
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AP_SerialManager::SerialProtocol_LTM_Telem, 0))) {
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_port->set_flow_control(AP_HAL::UARTDriver::FLOW_CONTROL_DISABLE);
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// initialise UART
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_port->begin(0, AP_SERIALMANAGER_LTM_BUFSIZE_RX,
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AP_SERIALMANAGER_LTM_BUFSIZE_TX);
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hal.scheduler->register_io_process(
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FUNCTOR_BIND_MEMBER(&AP_LTM_Telem::tick, void));
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}
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}
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void AP_LTM_Telem::send_LTM(uint8_t lt_packet[], uint8_t lt_packet_size)
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{
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// check space before write
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if (_port->txspace() < lt_packet_size) {
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return;
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}
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// calculate checksum
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uint8_t lt_crc = 0x00;
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for (uint8_t i = 3; i < lt_packet_size - 1; i++) {
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lt_crc ^= lt_packet[i];
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}
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lt_packet[lt_packet_size - 1] = lt_crc;
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_port->write(lt_packet, lt_packet_size);
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}
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// GPS frame
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void AP_LTM_Telem::send_Gframe(void)
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{
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const AP_GPS &gps = AP::gps();
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const uint8_t sats_visible = gps.num_sats();
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const uint8_t fix_type = (uint8_t)gps.status();
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int32_t lat = 0; // latitude
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int32_t lon = 0; // longtitude
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uint8_t gndspeed = 0; // gps ground speed (m/s)
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int32_t alt = 0;
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#if AP_AHRS_ENABLED
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{
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AP_AHRS &ahrs = AP::ahrs();
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WITH_SEMAPHORE(ahrs.get_semaphore());
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float alt_ahrs;
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ahrs.get_relative_position_D_home(alt_ahrs);
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alt = (int32_t) roundf(-alt_ahrs * 100.0); // altitude (cm)
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Location loc;
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if (ahrs.get_location(loc)) {
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lat = loc.lat;
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lon = loc.lng;
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gndspeed = (uint8_t) roundf(gps.ground_speed());
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}
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}
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#endif
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uint8_t lt_buff[LTM_GFRAME_SIZE];
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// protocol: START(2 bytes)FRAMEID(1byte)LAT(cm,4 bytes)LON(cm,4bytes)SPEED(m/s,1bytes)ALT(cm,4bytes)SATS(6bits)FIX(2bits)CRC(xor,1byte)
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// START
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lt_buff[0] = 0x24; //$
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lt_buff[1] = 0x54; //T
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// FRAMEID
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lt_buff[2] = 0x47; // G ( gps frame at 5hz )
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// PAYLOAD
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lt_buff[3] = (lat >> 8 * 0) & 0xFF;
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lt_buff[4] = (lat >> 8 * 1) & 0xFF;
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lt_buff[5] = (lat >> 8 * 2) & 0xFF;
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lt_buff[6] = (lat >> 8 * 3) & 0xFF;
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lt_buff[7] = (lon >> 8 * 0) & 0xFF;
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lt_buff[8] = (lon >> 8 * 1) & 0xFF;
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lt_buff[9] = (lon >> 8 * 2) & 0xFF;
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lt_buff[10] = (lon >> 8 * 3) & 0xFF;
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lt_buff[11] = (gndspeed >> 8 * 0) & 0xFF;
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lt_buff[12] = (alt >> 8 * 0) & 0xFF;
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lt_buff[13] = (alt >> 8 * 1) & 0xFF;
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lt_buff[14] = (alt >> 8 * 2) & 0xFF;
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lt_buff[15] = (alt >> 8 * 3) & 0xFF;
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lt_buff[16] = ((sats_visible << 2) & 0xFF)
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| ((fix_type > 3 ? 3 : fix_type) & 0b00000011); // last 6 bits: sats number, first 2:fix type (0, 1, 2, 3)
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send_LTM(lt_buff, LTM_GFRAME_SIZE);
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_ltm_scheduler++;
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}
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// Sensors frame
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void AP_LTM_Telem::send_Sframe(void)
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{
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#if AP_BATTERY_ENABLED
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const AP_BattMonitor &battery = AP::battery();
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const uint16_t volt = (uint16_t) roundf(battery.voltage() * 1000.0f); // battery voltage (expects value in mV)
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float current;
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if (!battery.current_amps(current)) {
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current = 0;
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}
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// note: max. current value we can send is 65.536 A
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const uint16_t amp = (uint16_t) roundf(current * 100.0f); // current sensor (expects value in hundredth of A)
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#else
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const uint16_t volt = 0;
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const uint16_t amp = 0;
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#endif
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// airspeed in m/s if available and enabled - even if not used - otherwise send 0
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uint8_t airspeed = 0; // airspeed sensor (m/s)
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#if AP_AIRSPEED_ENABLED
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const AP_Airspeed *aspeed = AP::airspeed();
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if (aspeed && aspeed->enabled()) {
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airspeed = (uint8_t) roundf(aspeed->get_airspeed());
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}
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#endif
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const uint8_t flightmode = AP_Notify::flags.flight_mode; // flight mode
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uint8_t rssi = 0; // radio RSSI (%a)
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#if AP_RSSI_ENABLED
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AP_RSSI *ap_rssi = AP_RSSI::get_singleton();
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if (ap_rssi) {
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rssi = ap_rssi->read_receiver_rssi_uint8();
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}
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#endif
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const uint8_t armstat = AP_Notify::flags.armed; // 0: disarmed, 1: armed
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const uint8_t failsafe = AP_Notify::flags.failsafe_radio; // 0: normal, 1: failsafe
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uint8_t lt_buff[LTM_SFRAME_SIZE];
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// START
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lt_buff[0] = 0x24; //$
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lt_buff[1] = 0x54; //T
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// FRAMEID
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lt_buff[2] = 0x53; //S
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// PAYLOAD
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lt_buff[3] = (volt >> 8 * 0) & 0xFF; // VBAT converted to mV
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lt_buff[4] = (volt >> 8 * 1) & 0xFF;
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lt_buff[5] = (amp >> 8 * 0) & 0xFF; // actual current instead of consumed mAh in regular LTM
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lt_buff[6] = (amp >> 8 * 1) & 0xFF;
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lt_buff[7] = (rssi >> 8 * 0) & 0xFF;
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lt_buff[8] = (airspeed >> 8 * 0) & 0xFF;
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lt_buff[9] = ((flightmode << 2) & 0xFF)
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| ((failsafe << 1) & 0b00000010) | (armstat & 0b00000001); // last 6 bits: flight mode, 2nd bit: failsafe, 1st bit: arm status.
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send_LTM(lt_buff, LTM_SFRAME_SIZE);
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_ltm_scheduler++;
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}
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// Attitude frame
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void AP_LTM_Telem::send_Aframe(void)
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{
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int16_t pitch;
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int16_t roll;
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int16_t heading;
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#if AP_AHRS_ENABLED
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{
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AP_AHRS &ahrs = AP::ahrs();
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WITH_SEMAPHORE(ahrs.get_semaphore());
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pitch = roundf(ahrs.pitch_sensor * 0.01); // attitude pitch in degrees
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roll = roundf(ahrs.roll_sensor * 0.01); // attitude roll in degrees
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heading = roundf(ahrs.yaw_sensor * 0.01); // heading in degrees
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}
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#else
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pitch = 0;
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roll = 0;
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heading = 0;
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#endif
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uint8_t lt_buff[LTM_AFRAME_SIZE];
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// A Frame: $T(2 bytes)A(1byte)PITCH(2 bytes)ROLL(2bytes)HEADING(2bytes)CRC(xor,1byte)
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// START
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lt_buff[0] = 0x24; //$
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lt_buff[1] = 0x54; //T
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// FRAMEID
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lt_buff[2] = 0x41; //A
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// PAYLOAD
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lt_buff[3] = (pitch >> 8 * 0) & 0xFF;
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lt_buff[4] = (pitch >> 8 * 1) & 0xFF;
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lt_buff[5] = (roll >> 8 * 0) & 0xFF;
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lt_buff[6] = (roll >> 8 * 1) & 0xFF;
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lt_buff[7] = (heading >> 8 * 0) & 0xFF;
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lt_buff[8] = (heading >> 8 * 1) & 0xFF;
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send_LTM(lt_buff, LTM_AFRAME_SIZE);
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_ltm_scheduler++;
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}
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// send LTM
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void AP_LTM_Telem::generate_LTM(void)
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{
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if (_ltm_scheduler & 1) { // is odd
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send_Aframe();
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} else { // is even
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if (_ltm_scheduler % 4 == 0) {
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send_Sframe();
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} else {
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send_Gframe();
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}
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}
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if (_ltm_scheduler > 9) {
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_ltm_scheduler = 1;
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}
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}
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void AP_LTM_Telem::tick(void)
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{
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uint32_t now = AP_HAL::millis();
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if (now - _last_frame_ms >= 100) {
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_last_frame_ms = now;
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generate_LTM();
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}
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}
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#endif // AP_LTM_TELEM_ENABLED
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