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Each packet sent during the communication is based on the following structure:

Byte #

Name

Description

0

Packet start (3Ah)

Data packet start

1

OpenMATID byte 1

Contains the low byte of the OpenMAT ID of the sensor to be communicated with. The default value of this ID is 1. The host sends out a GET / SET request to a specific LPMS sensor by using this ID, and the client answers to request also with the same ID. This ID can be adjusted by sending a SET command to the sensor firmware.

2

OpenMAT ID byte 2

High byte of the OpenMAT ID of the sensor.

3

Command # byte 1

Contains the low byte of the command to be performed by the data transmission.

4

Command # byte 2

High byte of the command number.

5

Packet data length byte 1

Contains the low byte of the packet data length to be transmitted in the packet data field.

6

Packet data length byte 2

High byte of the data length to be transmitted.

x

Packet data(n bytes)

If data length n not equal to zero, x = 6+1, 6+2…6+n.

Otherwise x = none.

This data field contains the packet data to be transferred with the transmission if the data length not equals to zero, otherwise the data field is empty.

7+n

LRC byte 1

The low byte of LRC checksum. To ensure the integrity of the transmitted data the LRC checksum is used. It is calculated in the following way:

LRC = sum(OpenMAT ID, Command, Package data length, and packet data byte no. 1 to no. x)

The calculated LRC is usually compared with the LRC transmitted from the remote device. If the two LRCs are not equal, and error is reported.

8+n

LRC byte 2

High byte of LRC check-sum.

9+n

Termination byte 1

0Dh

10+n

Termination byte 2

0Ah

Data Format in a Packet Data Field

Generally, data is sent in little-endian format, low order byte first, high order byte last. Data in the data fields of a packet can be encoded in several ways, depending on the type of information to be transmitted. In the following we list the most common data types. Other command-specific data types are explained in the command reference.

Identifier

Description

Int32

32-bit signed integer value

Int16

16-bit signed integer value

Float32

32-bit float value

Vector3f

3 element 32-bit float vector

Vector3i16

3 element 16-bit signed integer vector

Vector4f

4 element 32-bit float vector

Vector4i16

4 element 16-bit signed integer vector

Matrix3x3f

3x3 element float value matrix

Sensor Measurement Data in Streaming Mode

...

In 32-bit float transmission mode:

Chunk #

Data type

Sensor data

1

Float32

Timestamp (ms)

2

Vector3f

Raw (uncalibrated) gyroscope data (deg/s)

3

Vector3f

Raw (uncalibrated) accelerometer data (g)

4

Vector3f

Raw (uncalibrated) magnetometer data (T)

5

Vector3f

Angular velocity (rad/s)

6

Vector4f

Orientation quaternion (normalized)

7

Vector3f

Euler angle data (rad)

8

Vector3f

Linear acceleration data (m/s2)

9

Float32

Barometric pressure (mPa)

10

Float32

Altitude (m)

11

Float32

Temperature (°C)

12

Float32

Heave motion (m) (optional)

In 16-bit transmission mode values are transmitted to the host with a multiplication factor applied to increase precision:

Order #

Data type

Sensor data

Factor

1

uint32

Timestamp (s)

400

2

Vector3i16

Raw (uncalibrated) gyroscope data (rad/s)

1000

3

Vector3i16

Raw (uncalibrated) accelerometer data (g)

1000

4

Vector3i16

Raw (uncalibrated) magnetometer data (uT)

100

5

Vector3i16

Angular velocity (rad/s)

1000

6

Vector4i16

Orientation quaternion (normalized)

10000

7

Vector3i16

Euler angle data (rad)

10000

8

Vector3i16

Linear acceleration data (g)

1000

9

Int16

Barometric pressure (kPa)

100

10

Int16

Altitude (m)

10

11

Int16

Temperature (°C)

100

12

Int16

Heave motion (m) (optional)

1000

NOTE: Raw accelerometer data is transmitted with misalignment correction and scaling to g units applied. Raw gyroscope data is transmitted with misalignment correction, bias correction and scaling to rad/s applied. Raw magnetometer data is transmitted with misalignment correction and scaling to uT applied, hard and soft iron calibration is not applied to raw magnetometer data transmitted directly from sensor.

...

GET request (HOST -> SENSOR)

Packet byte no.

Content

Meaning

0

3Ah

Packet start

1

01h

OpenMAT ID LSB (ID = 1)

2

00h

OpenMAT ID MSB

3

04h

Command no. LSB (4d = GET_CONFIG)

4

00h

Command no. MSB

5

00h

Data length LSB (GET command = no data)

6

00h

Data length MSB

7

05h

Check sum LSB

8

00h

Check sum MSB

9

0Dh

Packet end 1

10

0Ah

Packet end 2

Reply data (SENSOR -> HOST)

Packet byte no.

Content

Meaning

0

3Ah

Packet start

1

01h

OpenMAT LSB (ID = 1)

2

00h

OpenMAT MSB

3

04h

Command no. LSB (4d = GET_CONFIG)

4

00h

Command no. MSB

5

04h

Data length LSB (32-bit integer = 4 bytes)

6

00h

Data length MSB

7

xxh

Configuration data byte 1 (LSB)

8

xxh

Configuration data byte 2

9

xxh

Configuration data byte 3

10

xxh

Configuration data byte 4 (MSB)

11

xxh

Check sum LSB

12

xxh

Check sum MSB

13

0Dh

Packet end 1

14

0Ah

Packet end 2

xx = Value depends on the current sensor configuration.

...

GET request (HOST -> SENSOR)

Packet byte no.

Content

Meaning

0

3Ah

Packet start

1

01h

OpenMAT ID LSB (ID = 1)

2

00h

OpenMAT ID MSB

3

1Ah

Command no. LSB (26d = GET_GYR_RANGE)

4

00h

Command no. MSB

5

00h

Data length LSB (GET command = no data)

6

00h

Data length MSB

7

1Bh

Check sum LSB

8

00h

Check sum MSB

9

0Dh

Packet end 1

10

0Ah

Packet end 2

Reply data (SENSOR -> HOST)

Packet byte no.

Content

Meaning

0

3Ah

Packet start

1

01h

OpenMAT ID LSB (ID = 1)

2

00h

OpenMAT ID MSB

3

1Ah

Command no. LSB (26d = GET_GYR_RANGE)

4

00h

Command no. MSB

5

04h

Data length LSB (32-bit integer = 4 bytes)

6

00h

Data length MSB

7

xxh

Range data byte 1 (LSB)

8

xxh

Range data byte 2

9

xxh

Range data byte 3

10

xxh

Range data byte 4 (MSB)

11

xxh

Check sum LSB

12

xxh

Check sum MSB

13

0Dh

Packet end 1

14

0Ah

Packet end 2

xx = Value depends on the current sensor configuration.

...

SET request (HOST -> SENSOR)

Packet byte no.

Content

Meaning

0

3Ah

Packet start

1

01h

OpenMAT ID LSB (ID = 1)

2

00h

OpenMAT ID MSB

3

1Fh

Command no. LSB (31d = SET_ACC_RANGE)

4

00h

Command no. MSB

5

04h

Data length LSB (32-bit integer = 4 bytes)

6

00h

Data length MSB

7

08h

Range data byte 1 (Range indicator 8g = 8d)

8

00h

Range data byte 2

9

00h

Range data byte 3

10

00h

Range data byte 4

11

2Bh

Check sum LSB

12

00h

Check sum MSB

13

0Dh

Packet end 1

14

0Ah

Packet end 2

Reply data (SENSOR -> HOST)

Packet byte no.

Content

Meaning

0

3Ah

Packet start

1

01h

OpenMAT ID LSB (ID = 1)

2

00h

OpenMAT ID MSB

3

00h

Command no. LSB (0d = REPLY_ACK)

4

00h

Command no. MSB

5

00h

Data length LSB (ACK reply = no data)

6

00h

Data length MSB

11

01h

Check sum LSB

12

00h

Check sum MSB

13

0Dh

Packet end 1

14

0Ah

Packet end 2

Read Sensor Data

Get request (HOST -> SENSOR)

Packet byte no.

Content

Meaning

0

3Ah

Packet start

1

01h

OpenMAT ID LSB (ID = 1)

2

00h

OpenMAT MSB

3

09h

Command no. LSB (9d = GET_SENSOR_DATA)

4

00h

Command no. MSB

5

00h

Data length LSB (GET command = no data)

6

00h

Data length MSB

7

0Ah

Check sum LSB

8

00h

Check sum MSB

9

0Dh

Packet end 1

10

0Ah

Packet end 2

Reply data (SENSOR -> HOST)

Packet byte no.

Content

Meaning

0

3Ah

Packet start

1

01h

OpenMAT ID LSB (ID = 1)

2

00h

OpenMAT ID MSB

3

09h

Command no. LSB (9d = GET_SENSOR_DATA)

4

00h

Command no. MSB

5

34h

Data length LSB (56 bytes)

6

00h

Data length MSB

7-10

xxxxxxxxh

Timestamp

11-14

xxxxxxxxh

Gyroscope data x-axis

15-18

xxxxxxxxh

Gyroscope data y-axis

19-22

xxxxxxxxh

Gyroscope data z-axis

23-26

xxxxxxxxh

Accelerometer x-axis

27-30

xxxxxxxxh

Accelerometer y-axis

31-34

xxxxxxxxh

Accelerometer z-axis

35-38

xxxxxxxxh

Magnetometer x-axis

39-42

xxxxxxxxh

Magnetometer y-axis

43-46

xxxxxxxxh

Magnetometer z-axis

47-50

xxxxxxxxh

Orientation quaternion q0

51-54

xxxxxxxxh

Orientation quaternion q1

55-58

xxxxxxxxh

Orientation quaternion q2

59-62

xxxxxxxxh

Orientation quaternion q3

63

xxh

Check sum LSB

64

xxh

Check sum MSB

65

0Dh

Message end byte 1

66

0Ah

Message end byte 2

xx = Value depends on the current configuration and measurement value.

...

In ASCII output mode sensor data is transmitted as plain ASCII numerical text. The output format for each number is generally 16-bit integer, but with a multiplication factor applied to increase precision. The following multiplication factors are used:

Chunk #

Data type

Sensor data

Factor

1

uint32

Timestamp (s)

10000

2

Vector3i16

Raw (

uncalibrated

bias calibrated) gyroscope data (

rad/s

dps)

1000

3

Vector3i16

Raw (uncalibrated) accelerometer data (g)

1000

4

Vector3i16

Raw (uncalibrated) magnetometer data (

T

uT)

1000

5

Vector3i16

Angular velocity (

rad/s

dps)

1000

6

Vector4i16

Orientation quaternion (normalized)

100000

7

Vector3i16

Euler angle data (

rad

deg)

1000

8

Vector3i16

Linear acceleration data (g)

1000

9

Int16

Barometric pressure (kPa)

1000

10

Int16

Altitude (m)

10

11

Int16

Temperature (°C)

100

12

Int16

Heave motion (m) (optional)

1000

LP-CAN Protocol

To exchange data with LPMS through the CAN Bus interface, the serial LP-BUS protocol is split into CAN bus messages. We call this CAN bus wrapper for the LP-BUS protocol: LP-CAN.

A regular LP-CAN message is structured as shown below:

11-bit CAN identifier

The CAN identifier of a CAN message. This identifier is set to the value 514h+OpenMAT ID of target sensor for all LP-CAN transmissions.

8 data bytes

Contains the actual data to be transmitted in a CAN message.

An example packet with 4 data bytes wrapping from LP-BUS to LP-CAN results in the following CAN messages:

CAN Message #1:

Byte #

Name

Description

0

Packet start (3Ah)

Mark of the beginning of a data packet.

1

OpenMATID - byte 1

Contains the low byte of the OpenMAT ID of the sensor to be communicated with. The default value of this ID is 1. The host sends out a GET / SET request to a specific sensor by using this ID, and the client answers to request alsowith the same ID. This ID can be adjusted by sending a SET command to the sensor firmware.

2

OpenMAT ID - byte 2

High byte of the OpenMAT ID of the sensor

3

Command no. - byte 1

Contains the low byte of the command to be performed by the data transmission

4

Command no. - byte 2

High byte of the command number

5

Packet data length - byte 1

Contains the low byte of the packet data length to be transmitted in the packet data field (in this example 4)

6

Packet data length - byte 2

High byte of the data length to be transmitted (in this example 0)

7

Packet data

Packet data byte 0

CAN Message #2:

Byte #

Name

Description

0

Packet data

Packet data byte 1

1

Packet data

Packet data byte 2

2

Packet data

Packet data byte 3

3

LRC byte 1

The low byte of LRC check-sum.

4

LRC byte 2

High byte of LRC check-sum.

5

Termination byte 1

0Dh

6

Termination byte 2

0Ah

7

Not used

0

The number of messages needed to contain the data depends on the length of the data to be transmitted. Each CAN message is 8 bytes long. Unused bytes of a message are filled with 0.

...

Therefore, using these parameters the following message formats can be adjusted:

Parameter settings

Resulting channel message setup

Channel mode = Sequential

Value mode = 16-bit fixed point (signed)

StartID = 514h

IMU ID = 1

CAN message #1:

Code Block
CAN ID = 514h
1st 16 bits: Channel 1 data
2nd 16 bits: Channel 2 data
3rd 16 bits: Channel 3 data
4th 16 bits: Channel 4 data

CAN message #2:

Code Block
CAN ID = 515h
1st 16 bits: Channel 5 data
2nd 16 bits: Channel 6 data
3rd 16 bits: Channel 7 data
4th 16 bits: Channel 8 data

CAN message #3:

Code Block
CAN ID = 516h
1st 16 bits: Channel 9 data
2nd 16 bits: Channel 10 data
3rd 16 bits: Channel 11 data
4th 16 bits: Channel 12 data

CAN message #4:

Code Block
CAN ID = 517h
1st 16 bits: Channel 13 data
2nd 16 bits: Channel 14 data
3rd 16 bits: Channel 15 data
4th 16 bits: Channel 16 data

Channel mode = Sequential

Value mode = 32-bit floating point

Start ID = 514h

IMU ID = 1

CAN message #1:

Code Block
CAN ID = 514h
1st 32 bits: Channel 1 data
2nd 32 bits: Channel 2 data

CAN message #2:

Code Block
CAN ID = 515h
1st 32 bits: Channel 3 data
2nd 32 bits: Channel 4 data

CAN message #3:

Code Block
CAN ID = 516h
1st 32 bits: Channel 5 data
2nd 32 bits: Channel 6 data

CAN message #4:

Code Block
CAN ID = 517h
1st 32 bits: Channel 7 data
2nd 32 bits: Channel 8 data

Channel mode = CANopen

Value mode = 16-bit fixed point (signed)

Start ID = 180h

IMU ID = 1

CAN message #1:

Code Block
CAN ID = 181h
1st 16 bits: Channel 1 data
2nd 16 bits: Channel 2 data
3rd 16 bits: Channel 3 data
4th 16 bits: Channel 4 data

CAN message #2:

Code Block
CAN ID = 281h
1st 16 bits: Channel 5 data
2nd 16 bits: Channel 6 data
3rd 16 bits: Channel 7 data
4th 16 bits: Channel 8 data

CAN message #3

Code Block
CAN ID = 381h
1st 16 bits: Channel 9 data
2nd 16 bits: Channel 10 data
3rd 16 bits: Channel 11 data
4th 16 bits: Channel 12 data

CAN message #4:

Code Block
CAN ID = 481h
1st 16 bits: Channel 13 data
2nd 16 bits: Channel 14 data
3rd 16 bits: Channel 15 data
4th 16 bits: Channel 16 data

Channel mode = CANopen

Value mode = 32-bit floating point

Start ID = 180h

IMU ID = 1

CAN message #1:

Code Block
CAN ID = 181h
1st 32 bits: Channel 1 data
2nd 32 bits: Channel 2 data

CAN message #2:

Code Block
CAN ID = 281h
1st 32 bits: Channel 3 data
2nd 32 bits: Channel 4 data

CAN message #3:

Code Block
CAN ID = 381h
1st 32 bits: Channel 5 data
2nd 32 bits: Channel 6 data

CAN message #4:

Code Block
CAN ID = 481h
1st 32 bits: Channel 7 data
2nd 32 bits: Channel 8 data

Transmitted units in 32-bit float mode:

Data type

Unit

Raw (uncalibrated) angular speed (gyroscope)

radians / s

Raw (uncalibrated) acceleration (accelerometer)

g

Raw (uncalibrated) magnetic field strength (magnetometer)

uT

Euler angle

radians

Linear acceleration

g

Quaternion

normalized units

In 16-bit integer modes values are multiplied with a constant factor after transmission to increase precision:

Data type

Unit

Factor

Raw (uncalibrated) angular speed (gyroscope)

radians / s

1000

Raw (uncalibrated) acceleration (accelerometer)

g

1000

Raw (uncalibrated) magnetic field strength (magnetometer)

uT

100

Angular Velocity

radians / s

1000

Quaternion

normalized units

10000

Euler angle

radians

10000

Linear acceleration

g

1000

Barometric pressure

kPa

100

Altitude

m

10

Temperature

°C

100

Heave motion (optional)

m

1000