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CAN Protocol

The CAN interface allows the output of the the µINS, µAHRS, and µIMU to be published on a CAN bus. The Inertial Sense CAN implementation is based on CAN2.0b specification and follows a specific structure and format which is outlined below. All of the CAN configuration is done using the data set DID_CAN_CONFIG.

Enable CAN

To enable the CAN bus interface on the uINS, set bit IO_CONFIG_G1G2_CAN_BUS in DID_FLASH_CONFIG.ioConfig. This bit can be set using the EvalTool >> Settings >> General >> DID_FLASH_CONFIG >> ioConfig >> Enable CAN Bus on G1,G2 option.

A CAN message is enabled by entering a non-zero value in the DID_CAN_CONFIG.can_period_mult field of the desired message. The can_period_mult field is an integer which is multiplied by the Data Source Update Rate to determine the message broadcast period. Set can_period_mult to zero disable message broadcasting.

In the image below the CID_INS_TIME message is set to broadcast data at 10 times the data source rate.

image-20191114164046742

The baud rate is configurable by setting the field DID_CAN_CONFIG.can_baudrate_kbps. The following standard baud rates are supported:

  • 20 kbps
  • 33 kbps
  • 50 kbps
  • 83 kbps
  • 100 kbps
  • 125 kbps
  • 200 kbps
  • 250 kbps
  • 500 kbps
  • 1000 kbps

The message ID for each message can be entered into the can_transmit_address field corresponding to the desired message.

*Note: Any message ID greater than 0x7FF will be transmitted in the extended ID format.

The values set in any field of DID_CAN_CONFIG are saved to flash when a 'Save Persistent' command is received by the module. For example, this can be done in the EvalTool by clicking the Save Persistent button in the Data Logs tab. When the module is turned on, all the fields will be repopulated with the saved values.

All messages are disabled when a Stop Streaming message is received by the module. However, the values in each field will be repopulated to the values present when a 'Save Persistent' command was last received.

Hardware

Inertial Sense module exposes the RxCAN and TxCAN pins. The selection and implementation of a CAN transceiver is left to the user.

Line Function
G1 RxCAN
G2 TxCAN

The Inertial Sense evaluation boards and Rugged unit have a built in transceiver.

CAN Data Sets (CIDs)

The CAN Data Sets, in the form of C structures, define the format of the output data. The data sets are defined in SDK\hw-libs\communications\CAN_comm.h of the InertialSense SDK. The CID data is selected data from the standard Inertial Sense DIDs. The data types generally have been changed and scaled to fit the CAN2.0 8 byte payload restrictions.

CID_INS_TIME

INS time output

is_can_time

GMT information

Field Type Description
week uint32_t GPS number of weeks since January 6th, 1980
timeOfWeek float GPS time of week (since Sunday morning) in seconds

CID_INS_STATUS

is_can_ins_status

INS status flags

Field Type Description
insStatus uint32_t INS status flags (see eInsStatusFlags)
hdwStatus uint32_t Hardware status flags (see eHdwStatusFlags)

CID_INS_EULER

is_can_ins_euler

Euler angles: roll, pitch, yaw in radians with respect to NED (scaled by 10000)

Field Type Description
theta1 int16_t Roll (4 decimal places precision)
theta2 int16_t Pitch (4 decimal places precision)
theta3 int16_t Yaw (4 decimal places precision)

CID_INS_QUATN2B

is_can_ins_quatn2b

Quaternion body rotation with respect to NED: W, X, Y, Z (scaled by 10000)

Field Type Description
qn2b1 int16_t W (4 decimal places precision)
qn2b2 int16_t X (4 decimal places precision)
qn2b3 int16_t Y (4 decimal places precision)
qn2b4 int16_t Z (4 decimal places precision)

CID_INS_QUATE2B

is_can_ins_quate2b

Quaternion body rotation with respect to ECEF: W, X, Y, Z (scaled by 10000)

Field Type Description
qe2b1 int16_t W (4 decimal places precision)
qe2b2 int16_t X (4 decimal places precision)
qe2b3 int16_t Y (4 decimal places precision)
qe2b4 int16_t Z (4 decimal places precision)

CID_INS_UVW

is_can_uvw

Velocity U, V, W in body frame in meters per second (scaled by 100).

Field Type Description
uvw1 int16_t U (2 decimal places precision)
uvw2 int16_t V (2 decimal places precision)
uvw3 int16_t W (2 decimal places precision)

CID_INS_VE

is_can_ve

Velocity in ECEF (earth-centered earth-fixed) frame in meters per second (scaled by 100).

Field Type Description
ve1 int16_t ve1 (2 decimal places precision)
ve2 int16_t ve2 (2 decimal places precision)
ve3 int16_t ve3 (2 decimal places precision)

CID_INS_LAT

is_can_ins_lat

WGS84 latitude.

Field Type Description
lat double Latitude (degrees) (more than 8 decimal places precision)

CID_INS_LON

is_can_ins_lon

WGS84 longitude.

Field Type Description
lon double Longitude (degrees) (more than 8 decimal places precision)

CID_INS_ALT

is_can_ins_alt

WGS84 height above ellipsoid and GPS status flags

Field Type Description
alt float Altitude (meters) (more than 8 decimal places precision)
status uint32_t (see eGpsStatus) GPS status: [0x000000xx] number of satellites used, [0x0000xx00] fix type, [0x00xx0000] status flags

CID_INS_NORTH_EAST

is_can_north_east

Offset from reference latitude, longitude, and altitude to current latitude, longitude, and altitude.

Type Field Description
float ned1 North (meters)
float ned2 East (meters)

CID_INS_DOWN

is_can_down

Down offset from reference LLA and INS status flags

Type Field Description
float ned3 Down (meters)
float insStatus INS status flags

CID_INS_ECEF_X

is_can_ecef_x

X Position in ECEF (earth-centered earth-fixed) frame.

Type Field Description
ecef1 double X (meters)

CID_INS_ECEF_Y

is_can_ecef_y

Y Position in ECEF (earth-centered earth-fixed) frame.

Type Field Description
ecef2 double Y (meters)

CID_INS_ECEF_Z

is_can_ecef_z

Z Position in ECEF (earth-centered earth-fixed) frame.

Type Field Description
ecef2 double Z (meters)

CID_INS_MSL

ins_can_msl

Height above Mean Sea Level

Type Field Description
msl float MSL (meters)

CID_PREINT_PX

is_can_preint_imu_px

Preintegrated IMU values delta theta and delta velocity (X axis), and Integral period in body/IMU frame of accelerometer 0.

Type Field Description
theta0 int16_t Delta theta (rad, scaled by 1000, 3 decimal places precision)
vel0 int16_t Delta velocity (m/s, scaled by 100, 2 decimal places precision)
dt uints16_t Integral Period (meters, scaled by 1000)

CID_PREINT_QY

is_can_preint_imu_qy

Preintegrated IMU values delta theta and delta velocity (Y axis), and Integral period in body/IMU frame of accelerometer 0.

Type Field Description
theta1 int16_t Delta theta (rad, scaled by 1000, 3 decimal places precision)
vel1 int16_t Delta velocity (m/s, scaled by 100, 2 decimal places precision)
dt uints16_t Integral Period (meters, scaled by 1000)

CID_PREINT_RZ

is_can_preint_imu_rz

Preintegrated IMU values delta theta and delta velocity (Z axis), and Integral period in body/IMU frame of accelerometer 0.

Type Field Description
theta2 int16_t Delta theta (rad, scaled by 1000, 3 decimal places precision)
vel2 int16_t Delta velocity (m/s, scaled by 100, 2 decimal places precision)
dt uints16_t Integral Period (meters, scaled by 1000)

CID_DUAL_PX

is_can_dual_imu_px

Dual IMU gyro and accelerometer values from accelerometer 0

Type Field Description
theta0 int16_t Theta (rad/s, scaled by 1000, 3 decimal places precision)
vel0 int16_t Acceleration (m/s2, scaled by 100, 2 decimal places precision)
status uints32_t IMU status (see eImuStatus)

CID_DUAL_QY

is_can_dual_imu_qy

Dual IMU gyro and accelerometer values from accelerometer 0

Type Field Description
theta1 int16_t Theta (rad/s, scaled by 1000, 3 decimal places precision)
vel1 int16_t Acceleration (m/s2, scaled by 100, 2 decimal places precision)
status uints32_t IMU status (see eImuStatus)

CID_DUAL_RZ

is_can_dual_imu_rz

Dual IMU gyro and accelerometer values from accelerometer 0

Type Field Description
theta2 int16_t Theta (rad/s, scaled by 1000, 3 decimal places precision)
vel2 int16_t Acceleration (m/s2, scaled by 100, 2 decimal places precision)
status uints32_t IMU status (see eImuStatus)

CID_GPS1_POS

is_can_gps1_pos_status

GPS CNO Mean and GPS status flags

Type Field Description
status uint32_t (see eGpsStatus) GPS status: [0x000000xx] number of satellites used, [0x0000xx00] fix type, [0x00xx0000] status flags
cnoMean uint32_t (dBHz) Average of all satellite carrier to noise ratios (signal strengths) that are non-zero

CID_GPS1_RTK_REL

is_can_gps1_rtk_rel

RTK-GPS performance metrics

Type Field Description
arRatio uint8_t Ambiguity resolution ratio factor for validation
differentialAge uint8_t Age of differential (seconds)
distanceToBase float Distance to Base (m)
headingToBase int16_t Angle from north to vectorToBase in local tangent plane. (rad, scaled by 1000)

CID_ROLL_ROLLRATE

is_can_roll_rollRate

Combination or INS roll estimation and preintegrated IMU of both accelerometers

Type Field Description
insRoll int16_t INS Roll (scaled by 10000, 4 decimal places precision)
pImu1 int16_t Delta theta (rad, scaled by 1000, 3 decimal places precision)
pImu2 int16_t Delta theta (rad, scaled by 1000, 3 decimal places precision)