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GPS.cpp
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GPS.cpp
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#include "Arduino.h"
#include "config.h"
#include "def.h"
#include "types.h"
#include "GPS.h"
#include "Serial.h"
#include "Sensors.h"
#include "MultiWii.h"
#if GPS
bool GPS_newFrame(char c);
#if defined(NMEA)
bool GPS_NMEA_newFrame(char c);
#endif
#if defined(UBLOX)
bool GPS_UBLOX_newFrame(uint8_t data);
bool UBLOX_parse_gps(void);
#endif
#if defined(MTK_BINARY16) || defined(MTK_BINARY19)
bool GPS_MTK_newFrame(uint8_t data);
#endif
void GPS_distance_cm_bearing(int32_t* lat1, int32_t* lon1, int32_t* lat2, int32_t* lon2,uint32_t* dist, int32_t* bearing);
static void GPS_calc_velocity(void);
static void GPS_calc_location_error( int32_t* target_lat, int32_t* target_lng, int32_t* gps_lat, int32_t* gps_lng );
static void GPS_calc_poshold(void);
static uint16_t GPS_calc_desired_speed(uint16_t max_speed, bool _slow);
static void GPS_calc_nav_rate(uint16_t max_speed);
int32_t wrap_18000(int32_t ang);
static bool check_missed_wp(void);
void GPS_calc_longitude_scaling(int32_t lat);
static void GPS_update_crosstrack(void);
int32_t wrap_36000(int32_t ang);
#if defined(INIT_MTK_GPS)
#define MTK_SET_BINARY PSTR("$PGCMD,16,0,0,0,0,0*6A\r\n")
#define MTK_SET_NMEA PSTR("$PGCMD,16,1,1,1,1,1*6B\r\n")
#define MTK_SET_NMEA_SENTENCES PSTR("$PMTK314,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0*28\r\n")
#define MTK_OUTPUT_4HZ PSTR("$PMTK220,250*29\r\n")
#define MTK_OUTPUT_5HZ PSTR("$PMTK220,200*2C\r\n")
#define MTK_OUTPUT_10HZ PSTR("$PMTK220,100*2F\r\n")
#define MTK_NAVTHRES_OFF PSTR("$PMTK397,0*23\r\n") // Set Nav Threshold (the minimum speed the GPS must be moving to update the position) to 0 m/s
#define SBAS_ON PSTR("$PMTK313,1*2E\r\n")
#define WAAS_ON PSTR("$PMTK301,2*2E\r\n")
#define SBAS_TEST_MODE PSTR("$PMTK319,0*25\r\n") //Enable test use of sbas satelite in test mode (usually PRN124 is in test mode)
#endif
#if defined(GPS_LEAD_FILTER)
// Set up gps lag
#if defined(UBLOX)
#define GPS_LAG 0.5f //UBLOX GPS has a smaller lag than MTK and other
#else
#define GPS_LAG 1.0f //We assumes that MTK GPS has a 1 sec lag
#endif
static int32_t GPS_coord_lead[2]; // Lead filtered gps coordinates
class LeadFilter {
public:
LeadFilter() :
_last_velocity(0) {
}
// setup min and max radio values in CLI
int32_t get_position(int32_t pos, int16_t vel, float lag_in_seconds = 1.0);
void clear() { _last_velocity = 0; }
private:
int16_t _last_velocity;
};
int32_t LeadFilter::get_position(int32_t pos, int16_t vel, float lag_in_seconds)
{
int16_t accel_contribution = (vel - _last_velocity) * lag_in_seconds * lag_in_seconds;
int16_t vel_contribution = vel * lag_in_seconds;
// store velocity for next iteration
_last_velocity = vel;
return pos + vel_contribution + accel_contribution;
}
LeadFilter xLeadFilter; // Long GPS lag filter
LeadFilter yLeadFilter; // Lat GPS lag filter
#endif
typedef struct PID_PARAM_ {
float kP;
float kI;
float kD;
float Imax;
} PID_PARAM;
PID_PARAM posholdPID_PARAM;
PID_PARAM poshold_ratePID_PARAM;
PID_PARAM navPID_PARAM;
typedef struct PID_ {
float integrator; // integrator value
int32_t last_input; // last input for derivative
float lastderivative; // last derivative for low-pass filter
float output;
float derivative;
} PID;
PID posholdPID[2];
PID poshold_ratePID[2];
PID navPID[2];
int32_t get_P(int32_t error, struct PID_PARAM_* pid) {
return (float)error * pid->kP;
}
int32_t get_I(int32_t error, float* dt, struct PID_* pid, struct PID_PARAM_* pid_param) {
pid->integrator += ((float)error * pid_param->kI) * *dt;
pid->integrator = constrain(pid->integrator,-pid_param->Imax,pid_param->Imax);
return pid->integrator;
}
int32_t get_D(int32_t input, float* dt, struct PID_* pid, struct PID_PARAM_* pid_param) { // dt in milliseconds
pid->derivative = (input - pid->last_input) / *dt;
/// Low pass filter cut frequency for derivative calculation.
float filter = 7.9577e-3; // Set to "1 / ( 2 * PI * f_cut )";
// Examples for _filter:
// f_cut = 10 Hz -> _filter = 15.9155e-3
// f_cut = 15 Hz -> _filter = 10.6103e-3
// f_cut = 20 Hz -> _filter = 7.9577e-3
// f_cut = 25 Hz -> _filter = 6.3662e-3
// f_cut = 30 Hz -> _filter = 5.3052e-3
// discrete low pass filter, cuts out the
// high frequency noise that can drive the controller crazy
pid->derivative = pid->lastderivative + (*dt / ( filter + *dt)) * (pid->derivative - pid->lastderivative);
// update state
pid->last_input = input;
pid->lastderivative = pid->derivative;
// add in derivative component
return pid_param->kD * pid->derivative;
}
void reset_PID(struct PID_* pid) {
pid->integrator = 0;
pid->last_input = 0;
pid->lastderivative = 0;
}
#define _X 1
#define _Y 0
#define RADX100 0.000174532925
#define CROSSTRACK_GAIN 1
#define NAV_SPEED_MIN 100 // cm/sec
#define NAV_SPEED_MAX 300 // cm/sec
#define NAV_SLOW_NAV true
#define NAV_BANK_MAX 3000 //30deg max banking when navigating (just for security and testing)
static float dTnav; // Delta Time in milliseconds for navigation computations, updated with every good GPS read
static uint16_t GPS_wp_radius = GPS_WP_RADIUS;
static int16_t actual_speed[2] = {0,0};
static float GPS_scaleLonDown; // this is used to offset the shrinking longitude as we go towards the poles
// The difference between the desired rate of travel and the actual rate of travel
// updated after GPS read - 5-10hz
static int16_t rate_error[2];
static int32_t error[2];
//Currently used WP
static int32_t GPS_WP[2];
////////////////////////////////////////////////////////////////////////////////
// Location & Navigation
////////////////////////////////////////////////////////////////////////////////
// This is the angle from the copter to the "next_WP" location in degrees * 100
static int32_t target_bearing;
////////////////////////////////////////////////////////////////////////////////
// Crosstrack
////////////////////////////////////////////////////////////////////////////////
// deg * 100, The original angle to the next_WP when the next_WP was set
// Also used to check when we pass a WP
static int32_t original_target_bearing;
// The amount of angle correction applied to target_bearing to bring the copter back on its optimum path
static int16_t crosstrack_error;
////////////////////////////////////////////////////////////////////////////////
// The location of the copter in relation to home, updated every GPS read (1deg - 100)
// static int32_t home_to_copter_bearing; /* unused */
// distance between plane and home in cm
// static int32_t home_distance; /* unused */
// distance between plane and next_WP in cm
static uint32_t wp_distance;
// used for slow speed wind up when start navigation;
static uint16_t waypoint_speed_gov;
////////////////////////////////////////////////////////////////////////////////////
// moving average filter variables
//
#define GPS_FILTER_VECTOR_LENGTH 5
static uint8_t GPS_filter_index = 0;
static int32_t GPS_filter[2][GPS_FILTER_VECTOR_LENGTH];
static int32_t GPS_filter_sum[2];
static int32_t GPS_read[2];
static int32_t GPS_filtered[2];
static int32_t GPS_degree[2]; //the lat lon degree without any decimals (lat/10 000 000)
static uint16_t fraction3[2];
// This is the angle from the copter to the "next_WP" location
// with the addition of Crosstrack error in degrees * 100
static int32_t nav_bearing;
// saves the bearing at takeof (1deg = 1) used to rotate to takeoff direction when arrives at home
static int16_t nav_takeoff_bearing;
#if defined(GPS_SERIAL)
#if defined(INIT_MTK_GPS) || defined(UBLOX)
uint32_t init_speed[5] = {9600,19200,38400,57600,115200};
void SerialGpsPrint(const char PROGMEM * str) {
char b;
while(str && (b = pgm_read_byte(str++))) {
SerialWrite(GPS_SERIAL, b);
#if defined(UBLOX)
delay(5);
#endif
}
}
#endif
#if defined(UBLOX)
prog_char UBLOX_INIT[] PROGMEM = { // PROGMEM array must be outside any function !!!
0xB5,0x62,0x06,0x01,0x03,0x00,0xF0,0x05,0x00,0xFF,0x19, //disable all default NMEA messages
0xB5,0x62,0x06,0x01,0x03,0x00,0xF0,0x03,0x00,0xFD,0x15,
0xB5,0x62,0x06,0x01,0x03,0x00,0xF0,0x01,0x00,0xFB,0x11,
0xB5,0x62,0x06,0x01,0x03,0x00,0xF0,0x00,0x00,0xFA,0x0F,
0xB5,0x62,0x06,0x01,0x03,0x00,0xF0,0x02,0x00,0xFC,0x13,
0xB5,0x62,0x06,0x01,0x03,0x00,0xF0,0x04,0x00,0xFE,0x17,
0xB5,0x62,0x06,0x01,0x03,0x00,0x01,0x02,0x01,0x0E,0x47, //set POSLLH MSG rate
0xB5,0x62,0x06,0x01,0x03,0x00,0x01,0x03,0x01,0x0F,0x49, //set STATUS MSG rate
0xB5,0x62,0x06,0x01,0x03,0x00,0x01,0x06,0x01,0x12,0x4F, //set SOL MSG rate
0xB5,0x62,0x06,0x01,0x03,0x00,0x01,0x12,0x01,0x1E,0x67, //set VELNED MSG rate
0xB5,0x62,0x06,0x16,0x08,0x00,0x03,0x07,0x03,0x00,0x51,0x08,0x00,0x00,0x8A,0x41, //set WAAS to EGNOS
0xB5, 0x62, 0x06, 0x08, 0x06, 0x00, 0xC8, 0x00, 0x01, 0x00, 0x01, 0x00, 0xDE, 0x6A //set rate to 5Hz
};
#endif
void GPS_SerialInit(void) {
SerialOpen(GPS_SERIAL,GPS_BAUD);
delay(1000);
#if defined(UBLOX)
for(uint8_t i=0;i<5;i++){
SerialOpen(GPS_SERIAL,init_speed[i]); // switch UART speed for sending SET BAUDRATE command (NMEA mode)
#if (GPS_BAUD==19200)
SerialGpsPrint(PSTR("$PUBX,41,1,0003,0001,19200,0*23\r\n")); // 19200 baud - minimal speed for 5Hz update rate
#endif
#if (GPS_BAUD==38400)
SerialGpsPrint(PSTR("$PUBX,41,1,0003,0001,38400,0*26\r\n")); // 38400 baud
#endif
#if (GPS_BAUD==57600)
SerialGpsPrint(PSTR("$PUBX,41,1,0003,0001,57600,0*2D\r\n")); // 57600 baud
#endif
#if (GPS_BAUD==115200)
SerialGpsPrint(PSTR("$PUBX,41,1,0003,0001,115200,0*1E\r\n")); // 115200 baud
#endif
while(!SerialTXfree(GPS_SERIAL)) delay(10);
}
delay(200);
SerialOpen(GPS_SERIAL,GPS_BAUD);
for(uint8_t i=0; i<sizeof(UBLOX_INIT); i++) { // send configuration data in UBX protocol
SerialWrite(GPS_SERIAL, pgm_read_byte(UBLOX_INIT+i));
delay(5); //simulating a 38400baud pace (or less), otherwise commands are not accepted by the device.
}
#elif defined(INIT_MTK_GPS) // MTK GPS setup
for(uint8_t i=0;i<5;i++){
SerialOpen(GPS_SERIAL,init_speed[i]); // switch UART speed for sending SET BAUDRATE command
#if (GPS_BAUD==19200)
SerialGpsPrint(PSTR("$PMTK251,19200*22\r\n")); // 19200 baud - minimal speed for 5Hz update rate
#endif
#if (GPS_BAUD==38400)
SerialGpsPrint(PSTR("$PMTK251,38400*27\r\n")); // 38400 baud
#endif
#if (GPS_BAUD==57600)
SerialGpsPrint(PSTR("$PMTK251,57600*2C\r\n")); // 57600 baud
#endif
#if (GPS_BAUD==115200)
SerialGpsPrint(PSTR("$PMTK251,115200*1F\r\n")); // 115200 baud
#endif
while(!SerialTXfree(GPS_SERIAL)) delay(80);
}
// at this point we have GPS working at selected (via #define GPS_BAUD) baudrate
// So now we have to set the desired mode and update rate (which depends on the NMEA or MTK_BINARYxx settings)
SerialOpen(GPS_SERIAL,GPS_BAUD);
SerialGpsPrint(MTK_NAVTHRES_OFF);
while(!SerialTXfree(GPS_SERIAL)) delay(80);
SerialGpsPrint(SBAS_ON);
while(!SerialTXfree(GPS_SERIAL)) delay(80);
SerialGpsPrint(WAAS_ON);
while(!SerialTXfree(GPS_SERIAL)) delay(80);
SerialGpsPrint(SBAS_TEST_MODE);
while(!SerialTXfree(GPS_SERIAL)) delay(80);
SerialGpsPrint(MTK_OUTPUT_5HZ); // 5 Hz update rate
#if defined(NMEA)
SerialGpsPrint(MTK_SET_NMEA_SENTENCES); // only GGA and RMC sentence
#endif
#if defined(MTK_BINARY19) || defined(MTK_BINARY16)
SerialGpsPrint(MTK_SET_BINARY);
#endif
#endif //elif init_mtk_gps
}
#endif //gps_serial
uint8_t GPS_NewData(void) {
uint8_t axis;
#if defined(I2C_GPS)
static uint8_t _i2c_gps_status;
//Do not use i2c_writereg, since writing a register does not work if an i2c_stop command is issued at the end
//Still investigating, however with separated i2c_repstart and i2c_write commands works... and did not caused i2c errors on a long term test.
GPS_numSat = (_i2c_gps_status & 0xf0) >> 4;
_i2c_gps_status = i2c_readReg(I2C_GPS_ADDRESS,I2C_GPS_STATUS_00); //Get status register
uint8_t *varptr;
#if defined(I2C_GPS_SONAR)
i2c_rep_start(I2C_GPS_ADDRESS<<1);
i2c_write(I2C_GPS_SONAR_ALT);
i2c_rep_start((I2C_GPS_ADDRESS<<1)|1);
varptr = (uint8_t *)&sonarAlt; // altitude (in cm? maybe)
*varptr++ = i2c_readAck();
*varptr = i2c_readNak();
#endif
if (_i2c_gps_status & I2C_GPS_STATUS_3DFIX) { //Check is we have a good 3d fix (numsats>5)
f.GPS_FIX = 1;
if (_i2c_gps_status & I2C_GPS_STATUS_NEW_DATA) { //Check about new data
GPS_Frame = 1;
i2c_rep_start(I2C_GPS_ADDRESS<<1);
i2c_write(I2C_GPS_LOCATION); //Start read from here 2x2 bytes distance and direction
i2c_rep_start((I2C_GPS_ADDRESS<<1)|1);
varptr = (uint8_t *)&GPS_coord[LAT]; // for latitude displaying
*varptr++ = i2c_readAck();
*varptr++ = i2c_readAck();
*varptr++ = i2c_readAck();
*varptr = i2c_readAck();
varptr = (uint8_t *)&GPS_coord[LON]; // for longitude displaying
*varptr++ = i2c_readAck();
*varptr++ = i2c_readAck();
*varptr++ = i2c_readAck();
*varptr = i2c_readNak();
i2c_rep_start(I2C_GPS_ADDRESS<<1);
i2c_write(I2C_GPS_GROUND_SPEED);
i2c_rep_start((I2C_GPS_ADDRESS<<1)|1);
varptr = (uint8_t *)&GPS_speed; // speed in cm/s for OSD
*varptr++ = i2c_readAck();
*varptr = i2c_readAck();
varptr = (uint8_t *)&GPS_altitude; // altitude in meters for OSD
*varptr++ = i2c_readAck();
*varptr = i2c_readAck();
varptr = (uint8_t *)&GPS_ground_course;
*varptr++ = i2c_readAck();
*varptr = i2c_readNak();
} else {
return 0;
}
} else {
f.GPS_FIX = 0;
return 0;
}
#endif
#if defined(GPS_SERIAL) || defined(GPS_FROM_OSD)
#if defined(GPS_SERIAL)
uint8_t c = SerialAvailable(GPS_SERIAL);
if (c==0) return 0;
while (c--) {
if (GPS_newFrame(SerialRead(GPS_SERIAL))) {
#elif defined(GPS_FROM_OSD)
{
if(GPS_update & 2) { // Once second bit of GPS_update is set, indicate new GPS datas is readed from OSD - all in right format.
GPS_update &= 1; // We have: GPS_fix(0-2), GPS_numSat(0-15), GPS_coord[LAT & LON](signed, in 1/10 000 000 degres), GPS_altitude(signed, in meters) and GPS_speed(in cm/s)
#endif
GPS_Frame = 1;
}
}
#endif
return 1;
}
uint8_t GPS_Compute(void) {
if (GPS_Frame == 0) return 0; else GPS_Frame = 0;
if (GPS_update == 1) GPS_update = 0; else GPS_update = 1;
if (f.GPS_FIX && GPS_numSat >= 5) {
#if !defined(DONT_RESET_HOME_AT_ARM)
if (!f.ARMED) {f.GPS_FIX_HOME = 0;}
#endif
if (!f.GPS_FIX_HOME && f.ARMED) {
GPS_reset_home_position();
}
//Apply moving average filter to GPS data
#if defined(GPS_FILTERING)
GPS_filter_index = (GPS_filter_index+1) % GPS_FILTER_VECTOR_LENGTH;
for (axis = 0; axis< 2; axis++) {
GPS_read[axis] = GPS_coord[axis]; //latest unfiltered data is in GPS_latitude and GPS_longitude
GPS_degree[axis] = GPS_read[axis] / 10000000; // get the degree to assure the sum fits to the int32_t
// How close we are to a degree line ? its the first three digits from the fractions of degree
// later we use it to Check if we are close to a degree line, if yes, disable averaging,
fraction3[axis] = (GPS_read[axis]- GPS_degree[axis]*10000000) / 10000;
GPS_filter_sum[axis] -= GPS_filter[axis][GPS_filter_index];
GPS_filter[axis][GPS_filter_index] = GPS_read[axis] - (GPS_degree[axis]*10000000);
GPS_filter_sum[axis] += GPS_filter[axis][GPS_filter_index];
GPS_filtered[axis] = GPS_filter_sum[axis] / GPS_FILTER_VECTOR_LENGTH + (GPS_degree[axis]*10000000);
if ( nav_mode == NAV_MODE_POSHOLD) { //we use gps averaging only in poshold mode...
if ( fraction3[axis]>1 && fraction3[axis]<999 ) GPS_coord[axis] = GPS_filtered[axis];
}
}
#endif
//dTnav calculation
//Time for calculating x,y speed and navigation pids
static uint32_t nav_loopTimer;
dTnav = (float)(millis() - nav_loopTimer)/ 1000.0;
nav_loopTimer = millis();
// prevent runup from bad GPS
dTnav = min(dTnav, 1.0);
//calculate distance and bearings for gui and other stuff continously - From home to copter
uint32_t dist;
int32_t dir;
GPS_distance_cm_bearing(&GPS_coord[LAT],&GPS_coord[LON],&GPS_home[LAT],&GPS_home[LON],&dist,&dir);
GPS_distanceToHome = dist/100;
GPS_directionToHome = dir/100;
if (!f.GPS_FIX_HOME) { //If we don't have home set, do not display anything
GPS_distanceToHome = 0;
GPS_directionToHome = 0;
}
//calculate the current velocity based on gps coordinates continously to get a valid speed at the moment when we start navigating
GPS_calc_velocity();
if (f.GPS_HOLD_MODE || f.GPS_HOME_MODE){ //ok we are navigating
//do gps nav calculations here, these are common for nav and poshold
#if defined(GPS_LEAD_FILTER)
GPS_distance_cm_bearing(&GPS_coord_lead[LAT],&GPS_coord_lead[LON],&GPS_WP[LAT],&GPS_WP[LON],&wp_distance,&target_bearing);
GPS_calc_location_error(&GPS_WP[LAT],&GPS_WP[LON],&GPS_coord_lead[LAT],&GPS_coord_lead[LON]);
#else
GPS_distance_cm_bearing(&GPS_coord[LAT],&GPS_coord[LON],&GPS_WP[LAT],&GPS_WP[LON],&wp_distance,&target_bearing);
GPS_calc_location_error(&GPS_WP[LAT],&GPS_WP[LON],&GPS_coord[LAT],&GPS_coord[LON]);
#endif
switch (nav_mode) {
case NAV_MODE_POSHOLD:
//Desired output is in nav_lat and nav_lon where 1deg inclination is 100
GPS_calc_poshold();
break;
case NAV_MODE_WP:
int16_t speed = GPS_calc_desired_speed(NAV_SPEED_MAX, NAV_SLOW_NAV); //slow navigation
// use error as the desired rate towards the target
//Desired output is in nav_lat and nav_lon where 1deg inclination is 100
GPS_calc_nav_rate(speed);
//Tail control
if (NAV_CONTROLS_HEADING) {
if (NAV_TAIL_FIRST) {
magHold = wrap_18000(nav_bearing-18000)/100;
} else {
magHold = nav_bearing/100;
}
}
// Are we there yet ?(within 2 meters of the destination)
if ((wp_distance <= GPS_wp_radius) || check_missed_wp()){ //if yes switch to poshold mode
nav_mode = NAV_MODE_POSHOLD;
if (NAV_SET_TAKEOFF_HEADING) { magHold = nav_takeoff_bearing; }
}
break;
}
} //end of gps calcs
}
}
void GPS_reset_home_position(void) {
if (f.GPS_FIX && GPS_numSat >= 5) {
GPS_home[LAT] = GPS_coord[LAT];
GPS_home[LON] = GPS_coord[LON];
GPS_calc_longitude_scaling(GPS_coord[LAT]); //need an initial value for distance and bearing calc
nav_takeoff_bearing = att.heading; //save takeoff heading
//Set ground altitude
f.GPS_FIX_HOME = 1;
}
}
//reset navigation (stop the navigation processor, and clear nav)
void GPS_reset_nav(void) {
uint8_t i;
for(i=0;i<2;i++) {
nav_rated[i] = 0;
nav[i] = 0;
reset_PID(&posholdPID[i]);
reset_PID(&poshold_ratePID[i]);
reset_PID(&navPID[i]);
nav_mode = NAV_MODE_NONE;
}
}
//Get the relevant P I D values and set the PID controllers
void GPS_set_pids(void) {
posholdPID_PARAM.kP = (float)conf.pid[PIDPOS].P8/100.0;
posholdPID_PARAM.kI = (float)conf.pid[PIDPOS].I8/100.0;
posholdPID_PARAM.Imax = POSHOLD_RATE_IMAX * 100;
poshold_ratePID_PARAM.kP = (float)conf.pid[PIDPOSR].P8/10.0;
poshold_ratePID_PARAM.kI = (float)conf.pid[PIDPOSR].I8/100.0;
poshold_ratePID_PARAM.kD = (float)conf.pid[PIDPOSR].D8/1000.0;
poshold_ratePID_PARAM.Imax = POSHOLD_RATE_IMAX * 100;
navPID_PARAM.kP = (float)conf.pid[PIDNAVR].P8/10.0;
navPID_PARAM.kI = (float)conf.pid[PIDNAVR].I8/100.0;
navPID_PARAM.kD = (float)conf.pid[PIDNAVR].D8/1000.0;
navPID_PARAM.Imax = POSHOLD_RATE_IMAX * 100;
}
//It was moved here since even i2cgps code needs it
int32_t wrap_18000(int32_t ang) {
if (ang > 18000) ang -= 36000;
if (ang < -18000) ang += 36000;
return ang;
}
// here is the onboard GPS code
////////////////////////////////////////////////////////////////////////////////////
//PID based GPS navigation functions
//Author : EOSBandi
//Based on code and ideas from the Arducopter team: Jason Short,Randy Mackay, Pat Hickey, Jose Julio, Jani Hirvinen
//Andrew Tridgell, Justin Beech, Adam Rivera, Jean-Louis Naudin, Roberto Navoni
////////////////////////////////////////////////////////////////////////////////////
// this is used to offset the shrinking longitude as we go towards the poles
// It's ok to calculate this once per waypoint setting, since it changes a little within the reach of a multicopter
//
void GPS_calc_longitude_scaling(int32_t lat) {
float rads = (abs((float)lat) / 10000000.0) * 0.0174532925;
GPS_scaleLonDown = cos(rads);
}
////////////////////////////////////////////////////////////////////////////////////
// Sets the waypoint to navigate, reset neccessary variables and calculate initial values
//
void GPS_set_next_wp(int32_t* lat, int32_t* lon) {
GPS_WP[LAT] = *lat;
GPS_WP[LON] = *lon;
GPS_calc_longitude_scaling(*lat);
GPS_distance_cm_bearing(&GPS_coord[LAT],&GPS_coord[LON],&GPS_WP[LAT],&GPS_WP[LON],&wp_distance,&target_bearing);
nav_bearing = target_bearing;
GPS_calc_location_error(&GPS_WP[LAT],&GPS_WP[LON],&GPS_coord[LAT],&GPS_coord[LON]);
original_target_bearing = target_bearing;
waypoint_speed_gov = NAV_SPEED_MIN;
}
////////////////////////////////////////////////////////////////////////////////////
// Check if we missed the destination somehow
//
static bool check_missed_wp(void) {
int32_t temp;
temp = target_bearing - original_target_bearing;
temp = wrap_18000(temp);
return (abs(temp) > 10000); // we passed the waypoint by 100 degrees
}
////////////////////////////////////////////////////////////////////////////////////
// Get distance between two points in cm
// Get bearing from pos1 to pos2, returns an 1deg = 100 precision
void GPS_distance_cm_bearing(int32_t* lat1, int32_t* lon1, int32_t* lat2, int32_t* lon2,uint32_t* dist, int32_t* bearing) {
float dLat = *lat2 - *lat1; // difference of latitude in 1/10 000 000 degrees
float dLon = (float)(*lon2 - *lon1) * GPS_scaleLonDown;
*dist = sqrt(sq(dLat) + sq(dLon)) * 1.113195;
*bearing = 9000.0f + atan2(-dLat, dLon) * 5729.57795f; //Convert the output redians to 100xdeg
if (*bearing < 0) *bearing += 36000;
}
//*******************************************************************************************************
// calc_velocity_and_filtered_position - velocity in lon and lat directions calculated from GPS position
// and accelerometer data
// lon_speed expressed in cm/s. positive numbers mean moving east
// lat_speed expressed in cm/s. positive numbers when moving north
// Note: we use gps locations directly to calculate velocity instead of asking gps for velocity because
// this is more accurate below 1.5m/s
// Note: even though the positions are projected using a lead filter, the velocities are calculated
// from the unaltered gps locations. We do not want noise from our lead filter affecting velocity
//*******************************************************************************************************
static void GPS_calc_velocity(void){
static int16_t speed_old[2] = {0,0};
static int32_t last[2] = {0,0};
static uint8_t init = 0;
if (init) {
float tmp = 1.0/dTnav;
actual_speed[_X] = (float)(GPS_coord[LON] - last[LON]) * GPS_scaleLonDown * tmp;
actual_speed[_Y] = (float)(GPS_coord[LAT] - last[LAT]) * tmp;
#if !defined(GPS_LEAD_FILTER)
actual_speed[_X] = (actual_speed[_X] + speed_old[_X]) / 2;
actual_speed[_Y] = (actual_speed[_Y] + speed_old[_Y]) / 2;
speed_old[_X] = actual_speed[_X];
speed_old[_Y] = actual_speed[_Y];
#endif
}
init=1;
last[LON] = GPS_coord[LON];
last[LAT] = GPS_coord[LAT];
#if defined(GPS_LEAD_FILTER)
GPS_coord_lead[LON] = xLeadFilter.get_position(GPS_coord[LON], actual_speed[_X], GPS_LAG);
GPS_coord_lead[LAT] = yLeadFilter.get_position(GPS_coord[LAT], actual_speed[_Y], GPS_LAG);
#endif
}
////////////////////////////////////////////////////////////////////////////////////
// Calculate a location error between two gps coordinates
// Because we are using lat and lon to do our distance errors here's a quick chart:
// 100 = 1m
// 1000 = 11m = 36 feet
// 1800 = 19.80m = 60 feet
// 3000 = 33m
// 10000 = 111m
//
static void GPS_calc_location_error( int32_t* target_lat, int32_t* target_lng, int32_t* gps_lat, int32_t* gps_lng ) {
error[LON] = (float)(*target_lng - *gps_lng) * GPS_scaleLonDown; // X Error
error[LAT] = *target_lat - *gps_lat; // Y Error
}
////////////////////////////////////////////////////////////////////////////////////
// Calculate nav_lat and nav_lon from the x and y error and the speed
//
static void GPS_calc_poshold(void) {
int32_t d;
int32_t target_speed;
uint8_t axis;
for (axis=0;axis<2;axis++) {
target_speed = get_P(error[axis], &posholdPID_PARAM); // calculate desired speed from lat/lon error
target_speed = constrain(target_speed,-100,100); // Constrain the target speed in poshold mode to 1m/s it helps avoid runaways..
rate_error[axis] = target_speed - actual_speed[axis]; // calc the speed error
nav[axis] =
get_P(rate_error[axis], &poshold_ratePID_PARAM)
+get_I(rate_error[axis] + error[axis], &dTnav, &poshold_ratePID[axis], &poshold_ratePID_PARAM);
d = get_D(error[axis], &dTnav, &poshold_ratePID[axis], &poshold_ratePID_PARAM);
d = constrain(d, -2000, 2000);
// get rid of noise
if(abs(actual_speed[axis]) < 50) d = 0;
nav[axis] +=d;
nav[axis] = constrain(nav[axis], -NAV_BANK_MAX, NAV_BANK_MAX);
navPID[axis].integrator = poshold_ratePID[axis].integrator;
}
}
////////////////////////////////////////////////////////////////////////////////////
// Calculate the desired nav_lat and nav_lon for distance flying such as RTH
//
static void GPS_calc_nav_rate(uint16_t max_speed) {
float trig[2];
uint8_t axis;
// push us towards the original track
GPS_update_crosstrack();
// nav_bearing includes crosstrack
float temp = (9000l - nav_bearing) * RADX100;
trig[_X] = cos(temp);
trig[_Y] = sin(temp);
for (axis=0;axis<2;axis++) {
rate_error[axis] = (trig[axis] * max_speed) - actual_speed[axis];
rate_error[axis] = constrain(rate_error[axis], -1000, 1000);
// P + I + D
nav[axis] =
get_P(rate_error[axis], &navPID_PARAM)
+get_I(rate_error[axis], &dTnav, &navPID[axis], &navPID_PARAM)
+get_D(rate_error[axis], &dTnav, &navPID[axis], &navPID_PARAM);
nav[axis] = constrain(nav[axis], -NAV_BANK_MAX, NAV_BANK_MAX);
poshold_ratePID[axis].integrator = navPID[axis].integrator;
}
}
////////////////////////////////////////////////////////////////////////////////////
// Calculating cross track error, this tries to keep the copter on a direct line
// when flying to a waypoint.
//
static void GPS_update_crosstrack(void) {
if (abs(wrap_18000(target_bearing - original_target_bearing)) < 4500) { // If we are too far off or too close we don't do track following
float temp = (target_bearing - original_target_bearing) * RADX100;
crosstrack_error = sin(temp) * (wp_distance * CROSSTRACK_GAIN); // Meters we are off track line
nav_bearing = target_bearing + constrain(crosstrack_error, -3000, 3000);
nav_bearing = wrap_36000(nav_bearing);
}else{
nav_bearing = target_bearing;
}
}
////////////////////////////////////////////////////////////////////////////////////
// Determine desired speed when navigating towards a waypoint, also implement slow
// speed rampup when starting a navigation
//
// |< WP Radius
// 0 1 2 3 4 5 6 7 8m
// ...|...|...|...|...|...|...|...|
// 100 | 200 300 400cm/s
// | +|+
// |< we should slow to 1.5 m/s as we hit the target
//
static uint16_t GPS_calc_desired_speed(uint16_t max_speed, bool _slow) {
// max_speed is default 400 or 4m/s
if(_slow){
max_speed = min(max_speed, wp_distance / 2);
//max_speed = max(max_speed, 0);
}else{
max_speed = min(max_speed, wp_distance);
max_speed = max(max_speed, NAV_SPEED_MIN); // go at least 100cm/s
}
// limit the ramp up of the speed
// waypoint_speed_gov is reset to 0 at each new WP command
if(max_speed > waypoint_speed_gov){
waypoint_speed_gov += (int)(100.0 * dTnav); // increase at .5/ms
max_speed = waypoint_speed_gov;
}
return max_speed;
}
////////////////////////////////////////////////////////////////////////////////////
// Utilities
//
int32_t wrap_36000(int32_t ang) {
if (ang > 36000) ang -= 36000;
if (ang < 0) ang += 36000;
return ang;
}
// This code is used for parsing NMEA data
#if defined(GPS_SERIAL)
/*
The latitude or longitude is coded this way in NMEA frames
dm.f coded as degrees + minutes + minute decimal
Where:
- d can be 1 or more char long. generally: 2 char long for latitude, 3 char long for longitude
- m is always 2 char long
- f can be 1 or more char long
This function converts this format in a unique unsigned long where 1 degree = 10 000 000
EOS increased the precision here, even if we think that the gps is not precise enough, with 10e5 precision it has 76cm resolution
with 10e7 it's around 1 cm now. Increasing it further is irrelevant, since even 1cm resolution is unrealistic, however increased
resolution also increased precision of nav calculations
*/
#define DIGIT_TO_VAL(_x) (_x - '0')
uint32_t GPS_coord_to_degrees(char* s) {
char *p, *q;
uint8_t deg = 0, min = 0;
unsigned int frac_min = 0;
uint8_t i;
// scan for decimal point or end of field
for (p = s; isdigit(*p); p++) ;
q = s;
// convert degrees
while ((p - q) > 2) {
if (deg)
deg *= 10;
deg += DIGIT_TO_VAL(*q++);
}
// convert minutes
while (p > q) {
if (min)
min *= 10;
min += DIGIT_TO_VAL(*q++);
}
// convert fractional minutes
// expect up to four digits, result is in
// ten-thousandths of a minute
if (*p == '.') {
q = p + 1;
for (i = 0; i < 4; i++) {
frac_min *= 10;
if (isdigit(*q))
frac_min += *q++ - '0';
}
}
return deg * 10000000UL + (min * 1000000UL + frac_min*100UL) / 6;
}
// helper functions
uint16_t grab_fields(char* src, uint8_t mult) { // convert string to uint16
uint8_t i;
uint16_t tmp = 0;
for(i=0; src[i]!=0; i++) {
if(src[i] == '.') {
i++;
if(mult==0) break;
else src[i+mult] = 0;
}
tmp *= 10;
if(src[i] >='0' && src[i] <='9') tmp += src[i]-'0';
}
return tmp;
}
uint8_t hex_c(uint8_t n) { // convert '0'..'9','A'..'F' to 0..15
n -= '0';
if(n>9) n -= 7;
n &= 0x0F;
return n;
}
bool GPS_newFrame(char c) {
#if defined(NMEA)
return GPS_NMEA_newFrame(c);
#endif
#if defined(UBLOX)
return GPS_UBLOX_newFrame(c);
#endif
#if defined(MTK_BINARY16) || defined(MTK_BINARY19)
return GPS_MTK_newFrame(c);
#endif
}
#if defined(NMEA)
/* This is a light implementation of a GPS frame decoding
This should work with most of modern GPS devices configured to output NMEA frames.
It assumes there are some NMEA GGA frames to decode on the serial bus
Here we use only the following data :
- latitude
- longitude
- GPS fix is/is not ok
- GPS num sat (4 is enough to be +/- reliable)
- GPS altitude
- GPS speed
*/
#define FRAME_GGA 1
#define FRAME_RMC 2
bool GPS_NMEA_newFrame(char c) {
uint8_t frameOK = 0;
static uint8_t param = 0, offset = 0, parity = 0;
static char string[15];
static uint8_t checksum_param, frame = 0;
if (c == '$') {
param = 0; offset = 0; parity = 0;
} else if (c == ',' || c == '*') {
string[offset] = 0;
if (param == 0) { //frame identification
frame = 0;
if (string[0] == 'G' && string[1] == 'P' && string[2] == 'G' && string[3] == 'G' && string[4] == 'A') frame = FRAME_GGA;
if (string[0] == 'G' && string[1] == 'P' && string[2] == 'R' && string[3] == 'M' && string[4] == 'C') frame = FRAME_RMC;
} else if (frame == FRAME_GGA) {
if (param == 2) {GPS_coord[LAT] = GPS_coord_to_degrees(string);}
else if (param == 3 && string[0] == 'S') GPS_coord[LAT] = -GPS_coord[LAT];
else if (param == 4) {GPS_coord[LON] = GPS_coord_to_degrees(string);}
else if (param == 5 && string[0] == 'W') GPS_coord[LON] = -GPS_coord[LON];
else if (param == 6) {f.GPS_FIX = (string[0] > '0');}
else if (param == 7) {GPS_numSat = grab_fields(string,0);}
else if (param == 9) {GPS_altitude = grab_fields(string,0);} // altitude in meters added by Mis
} else if (frame == FRAME_RMC) {
if (param == 7) {GPS_speed = ((uint32_t)grab_fields(string,1)*5144L)/1000L;} //gps speed in cm/s will be used for navigation
else if (param == 8) {GPS_ground_course = grab_fields(string,1); } //ground course deg*10
}
param++; offset = 0;
if (c == '*') checksum_param=1;
else parity ^= c;
} else if (c == '\r' || c == '\n') {
if (checksum_param) { //parity checksum
uint8_t checksum = hex_c(string[0]);
checksum <<= 4;
checksum += hex_c(string[1]);
if (checksum == parity) frameOK = 1;
}
checksum_param=0;
} else {
if (offset < 15) string[offset++] = c;
if (!checksum_param) parity ^= c;
}
if (frame) GPS_Present = 1;
return frameOK && (frame==FRAME_GGA);
}
#endif //NMEA
#if defined(UBLOX)
struct ubx_header {
uint8_t preamble1;
uint8_t preamble2;
uint8_t msg_class;
uint8_t msg_id;
uint16_t length;
};
struct ubx_nav_posllh {
uint32_t time; // GPS msToW
int32_t longitude;
int32_t latitude;
int32_t altitude_ellipsoid;
int32_t altitude_msl;
uint32_t horizontal_accuracy;
uint32_t vertical_accuracy;
};
struct ubx_nav_solution {
uint32_t time;
int32_t time_nsec;
int16_t week;
uint8_t fix_type;
uint8_t fix_status;
int32_t ecef_x;
int32_t ecef_y;
int32_t ecef_z;
uint32_t position_accuracy_3d;
int32_t ecef_x_velocity;
int32_t ecef_y_velocity;
int32_t ecef_z_velocity;
uint32_t speed_accuracy;
uint16_t position_DOP;
uint8_t res;
uint8_t satellites;
uint32_t res2;
};
struct ubx_nav_velned {
uint32_t time; // GPS msToW
int32_t ned_north;
int32_t ned_east;
int32_t ned_down;
uint32_t speed_3d;
uint32_t speed_2d;
int32_t heading_2d;
uint32_t speed_accuracy;
uint32_t heading_accuracy;
};
enum ubs_protocol_bytes {
PREAMBLE1 = 0xb5,
PREAMBLE2 = 0x62,
CLASS_NAV = 0x01,
CLASS_ACK = 0x05,
CLASS_CFG = 0x06,
MSG_ACK_NACK = 0x00,
MSG_ACK_ACK = 0x01,
MSG_POSLLH = 0x2,
MSG_STATUS = 0x3,
MSG_SOL = 0x6,
MSG_VELNED = 0x12,
MSG_CFG_PRT = 0x00,
MSG_CFG_RATE = 0x08,
MSG_CFG_SET_RATE = 0x01,
MSG_CFG_NAV_SETTINGS = 0x24
};
enum ubs_nav_fix_type {
FIX_NONE = 0,
FIX_DEAD_RECKONING = 1,
FIX_2D = 2,
FIX_3D = 3,
FIX_GPS_DEAD_RECKONING = 4,
FIX_TIME = 5
};
enum ubx_nav_status_bits {
NAV_STATUS_FIX_VALID = 1
};
// Packet checksum accumulators
static uint8_t _ck_a;
static uint8_t _ck_b;
// State machine state