VEX GPS Sensor C API

Note

For a pros-specific usage guide on the GPS, please check out our article here.

Functions

gps_initialize_full

Set the GPS’s offset relative to the center of turning in meters, as well as its initial position.

This function uses the following values of errno when an error state is reached:

  • ENXIO - The given value is not within the range of V5 ports (1-21).
  • ENODEV - The port cannot be configured as a GPS.
  • EAGAIN - The sensor is still calibrating.
int32_t gps_initialize_full(uint8_t port, double xInitial, double yInitial, double headingInitial, double xOffset,
                   double yOffset)
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#define GPS_PORT 1
#define X_OFFSET .225
#define Y_OFFSET .223
#define X_INITIAL 1.54
#define Y_INITIAL 1.14
#define HEADING_INITIAL 90

void initialize() {
    gps_initialize_full(GPS_PORT, X_OFFSET, Y_OFFSET, X_INITIAL, Y_INITIAL, HEADING_INITIAL);
}
Parameters  
port The V5 GPS port number from (1-21)
xOffset Cartesian 4-Quadrant X offset from center of turning (meters)
yOffset Cartesian 4-Quadrant Y offset from center of turning (meters)
xInitial Initial 4-Quadrant X Position, with (0,0) being at the center of the field (meters)
yInitial Initial 4-Quadrant Y Position, with (0,0) being at the center of the field (meters)
headingInitial Heading with 0 being north on the field, in degrees [0,360) going clockwise

Returns: 1 if the operation was successful or PROS_ERR if the operation failed, setting errno.


gps_set_offset

Set the GPS’s offset relative to the center of turning in meters.

This function uses the following values of errno when an error state is reached:

  • ENXIO - The given value is not within the range of V5 ports (1-21).
  • ENODEV - The port cannot be configured as a GPS.
  • EAGAIN - The sensor is still calibrating.
int32_t gps_set_offset(uint8_t port, double xOffset, double yOffset)
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#define GPS_PORT 1
#define X_OFFSET -.225
#define Y_OFFSET .225

void initialize() {
    gps_set_offset(GPS_PORT, X_OFFSET, Y_OFFSET);
}
Parameters  
port The V5 GPS port number from (1-21)
xOffset Cartesian 4-Quadrant X offset from center of turning (meters)
yOffset Cartesian 4-Quadrant Y offset from center of turning (meters)

Returns: 1 if the operation was successful or PROS_ERR if the operation failed, setting errno.


gps_get_offset

Get the GPS’s location relative to the center of turning/origin in meters.

This function uses the following values of errno when an error state is reached:

  • ENXIO - The given value is not within the range of V5 ports (1-21).
  • ENODEV - The port cannot be configured as a GPS.
  • EAGAIN - The sensor is still calibrating.
int32_t gps_get_offset(uint8_t port, double* xOffset, double* yOffset)
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#define GPS_PORT 1

void opcontrol() {
    int *x;
    int *y;

    while (true) {
        gps_get_offset(GPS_PORT, x, y);
        screen_print(TEXT_MEDIUM, 1, "X Offset: %4d, Y Offset: %4d", *x, *y);
        delay(20);
    }
}
Parameters  
port The V5 GPS port number from (1-21)
xOffset Pointer to cartesian 4-Quadrant X offset from center of turning (meters)
yOffset Pointer to cartesian 4-Quadrant X offset from center of turning (meters)

Returns: 1 if the operation was successful or PROS_ERR if the operation failed, setting errno.


gps_set_position

Sets the robot’s location relative to the center of the field in meters.

This function uses the following values of errno when an error state is reached:

  • ENXIO - The given value is not within the range of V5 ports (1-21).
  • ENODEV - The port cannot be configured as a GPS.
  • EAGAIN - The sensor is still calibrating.
int32_t gps_set_position(uint8_t port, double xInitial, double yInitial, double headingInitial)
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#define GPS_PORT 1
#define X_INITIAL -1.15
#define Y_INITIAL 1.45
#define HEADING_INITIAL 90

void initialize() {
    gps_set_position(GPS_PORT, X_INITIAL, Y_INITIAL, HEADING_INITIAL);
}
Parameters  
port The V5 GPS port number from (1-21)
xInitial Initial 4-Quadrant X Position, with (0,0) being at the center of the field (meters)
yInitial Initial 4-Quadrant Y Position, with (0,0) being at the center of the field (meters)
headingInitial Heading with 0 being north on the field, in degrees [0,360) going clockwise

Returns: 1 if the operation was successful or PROS_ERR if the operation failed, setting errno.


gps_set_data_rate

Set the GPS sensor’s data rate in milliseconds, only applies to IMU on GPS.

This function uses the following values of errno when an error state is reached:

  • ENXIO - The given value is not within the range of V5 ports (1-21).
  • ENODEV - The port cannot be configured as a GPS.
  • EAGAIN - The sensor is still calibrating.
int32_t gps_set_data_rate(uint8_t port, uint32_t rate)
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#define GPS_PORT 1
#define GPS_DATA_RATE 5

void initialize() {
    gps_set_data_rate(GPS_PORT, GPS_DATA_RATE);
}
Parameters  
port The V5 GPS port number from (1-21)
rate Data rate in milliseconds (Minimum: 5 ms)

Returns: 1 if the operation was successful or PROS_ERR if the operation failed, setting errno.


gps_get_error

Get the possible RMS (Root Mean Squared) error in meters for GPS position.

This function uses the following values of errno when an error state is reached:

  • ENXIO - The given value is not within the range of V5 ports (1-21).
  • ENODEV - The port cannot be configured as a GPS.
  • EAGAIN - The sensor is still calibrating.
double gps_get_error(uint8_t port)
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#define GPS_PORT 1

void opcontrol() {
    double error;
    error = gps_get_error(GPS_PORT);
}
Parameters  
port The V5 GPS port number from (1-21)

Returns: Possible RMS (Root Mean Squared) error in meters for GPS position. If the operation failed, returns PROS_ERR_F and errno is set.


gps_get_status

Gets the position and roll, yaw, and pitch of the GPS.

This function uses the following values of errno when an error state is reached:

  • ENXIO - The given value is not within the range of V5 ports (1-21).
  • ENODEV - The port cannot be configured as a GPS.
  • EAGAIN - The sensor is still calibrating.
gps_status_s_t gps_get_status(uint8_t port)
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#define GPS_PORT 1

void opcontrol() {
    struct gps_status_s_t status;

    while (true) {
        status = gps_get_status(GPS_PORT);
        screen_print(TEXT_MEDIUM, 1, "x: %3f, y: %3f, pitch: %3f, status.x, status.y);
        screen_print(TEXT_MEDIUM, 2, "yaw: %3f, roll: %3f", status.pitch, status.yaw);
        screen_print(TEXT_MEDIUM, 3, "roll: %3f", status.roll);
        delay(20);
    }
}
Parameters  
port The V5 GPS port number from (1-21)

Returns: A struct (gps_status_s_t) containing values mentioned above. If the operation failed, all the structure’s members are filled with PROS_ERR_F and errno is set.


gps_get_heading

Get the heading in [0,360) degree values.

This function uses the following values of errno when an error state is reached:

  • ENXIO - The given value is not within the range of V5 ports (1-21).
  • ENODEV - The port cannot be configured as a GPS.
  • EAGAIN - The sensor is still calibrating.
double gps_get_heading(uint8_t port)
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#define GPS_PORT 1

void opcontrol() {
    double heading;

    while (true) {
        heading = gps_get_heading(GPS_PORT);
        delay(20);
    }
}
Parameters  
port The V5 GPS port number from (1-21)

Returns: The heading in [0,360) degree values. If the operation failed, returns PROS_ERR_F and errno is set.


gps_get_heading_raw

Get the heading in the max double value and min double value scale.

This function uses the following values of errno when an error state is reached:

  • ENXIO - The given value is not within the range of V5 ports (1-21).
  • ENODEV - The port cannot be configured as a GPS.
  • EAGAIN - The sensor is still calibrating.
double gps_get_heading_raw(uint8_t port)
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#define GPS_PORT 1

void opcontrol() {
    double heading;

    while (true) {
        heading = gps_get_heading_raw(GPS_PORT);
        delay(20);
    }
}
Parameters  
port The V5 GPS port number from (1-21)

Returns: The heading in [DOUBLE_MIN, DOUBLE_MAX] values. If the operation fails, returns PROS_ERR_F and errno is set.


gps_get_rotation

Gets the GPS sensor’s elapsed rotation value.

This function uses the following values of errno when an error state is reached:

  • ENXIO - The given value is not within the range of V5 ports (1-21).
  • ENODEV - The port cannot be configured as a GPS.
  • EAGAIN - The sensor is still calibrating.
double gps_get_rotation(uint8_t port)
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#define GPS_PORT 1

void opcontrol() {
    double elapsed_rotation;

    elapsed_rotation = gps_get_rotation(GPS_PORT);
}
Parameters  
port The V5 GPS port number from (1-21)

Returns: The elased heading in degrees. If the operation fails, returns PROS_ERR_F and errno is set.


gps_set_rotation

Set the GPS sensor’s rotation value to target value

This function uses the following values of errno when an error state is reached:

  • ENXIO - The given value is not within the range of V5 ports (1-21).
  • ENODEV - The port cannot be configured as a GPS.
  • EAGAIN - The sensor is still calibrating.
int32_t gps_set_rotation(uint8_t port, double target)
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#define GPS_PORT 1

void opcontrol() {
    gps_set_rotation(GPS_PORT, 60);
}
Parameters  
port The V5 GPS port number from (1-21)
target Target rotation value to set rotation value to

Returns: 1 if the operation was successful or PROS_ERR if the operation failed, setting errno.


gps_tare_rotation

Tare the GPS sensor’s rotation value.

This function uses the following values of errno when an error state is reached:

  • ENXIO - The given value is not within the range of V5 ports (1-21).
  • ENODEV - The port cannot be configured as a GPS.
  • EAGAIN - The sensor is still calibrating.
int32_t gps_tare_rotation(uint8_t port)
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#define GPS_PORT 1

void initialize() {
    gps_tare_rotation(GPS_PORT);
}
Parameters  
port The V5 GPS port number from (1-21)

Returns: 1 if the operation was successful or PROS_ERR if the operation failed, setting errno.


gps_get_gyro_rate

Get the GPS’s raw gyroscope values.

This function uses the following values of errno when an error state is reached:

  • ENXIO - The given value is not within the range of V5 ports (1-21).
  • ENODEV - The port cannot be configured as a GPS.
  • EAGAIN - The sensor is still calibrating.
gps_gyro_s_t gps_get_gyro_rate(uint8_t port)
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#define GPS_PORT 1

void opcontrol() {
    struct gps_gyro_s_t gyro;

    while (true) {
        gyro = gps_get_gyro_rate(GPS_PORT);
        screen_print(TEXT_MEDIUM, 1, "gyroscope- x: %3f, y: %3f, z: %3f", gyro.x, gyro.y, gyro.z);
        delay(20);
    }
}
Parameters  
port The V5 GPS port number from (1-21)

Returns: The raw gyroscope values. If the operation failed, all the structure’s members are filled with PROS_ERR_F and errno is set.


gps_get_accel

Get the GPS’s raw accelerometer values.

This function uses the following values of errno when an error state is reached:

  • ENXIO - The given value is not within the range of V5 ports (1-21).
  • ENODEV - The port cannot be configured as a GPS.
  • EAGAIN - The sensor is still calibrating.
gps_accel_s_t gps_get_accel(uint8_t port)
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#define GPS_PORT 1

void opcontrol() {
    struct gps_accel_s_t accel;

    while (true) {
        accel = gps_get_accel(GPS_PORT);
        screen_print(TEXT_MEDIUM, 1, "accleration- x: %3f, y: %3f, z: %3f", accel.x, accel.y, accel.z);
    }
}
Parameters  
port The V5 GPS port number from (1-21)

Returns: The raw accelerometer values. If the operation failed, all the structure’s members are filled with PROS_ERR_F and errno is set.


Macros

None.

Structures

gps_status_s_t

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typedef struct __attribute__((__packed__)) gps_status_s {
      double x;
      double y;
      double pitch;
      double roll;
      double yaw;
} gps_status_s_t;
Value  
x X Position (meters)
y Y Position (meters)
pitch Percieved Pitch based on GPS and IMU
roll Percieved Roll based on GPS and IMU
yaw Percieved Yaw based on GPS and IMU

gps_raw_s

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struct gps_raw_s {
      double x;
      double y;
      double z;
};
Value  
x Raw GPS Pitch
y Raw GPS Roll
z Raw GPS Yaw

gps_accel_s_t

typedef struct gps_raw_s gps_accel_s_t;

gps_gyro_s_t

typedef struct gps_raw_s gps_gyro_s_t;