LPMS3 CAN Bus data parsing

1 CANOpen and Sequential CAN Protocols
2 CAN Data Output Format
3 Example

LPMS CAN sensors can be configurde to output sensor data in either CANOpen or sequential CAN transmission mode to hte CAN Bus. The following sections explains the details of the output data.

CANOpen and Sequential CAN Protocols

In CANOpen and sequential CAN transmission modes, two or more output words of measurement data can be assigned to a CAN channel. In sequential CAN mode the channel addressing can be individually controlled. In CANOpen mode, 4 TPDO (Transmission Data Process Object) messages and a heartbeat message are transmitted.

NOTE: In CANOpen mode a heartbeat message is transmitted with a frequency between 0.1 Hz and 2 Hz.

In CANOpen mode, the message base address is calculated in the following way:
CAN ID1 = Base CAN ID = Start ID + IMU ID
CAN ID2 = CAN ID1 + 100h
CAN ID3 = CAN ID2 + 100h
CAN ID4 = CAN ID3 + 100h
CAN ID5 = 700h + IMU ID

Note: In CANOpen mode, Start ID is fixed at 180h

In sequential CAN mode, the message base address is calculated in the following way:
CAN ID1 = Base CAN ID = Start ID + IMU ID
CAN ID2 = CAN ID1 + 1h
CAN ID3 = CAN ID2 + 1h
CAN ID4 = CAN ID3 + 1h

NOTE: In sequential CAN mode, Start ID is set to 514h (1300d) by default. This value can be changed via LpmsControl2 interface

CAN Data Output Format

Each CAN message can be assigned multiple channels representing the sensor data. The number of assignable sensor data will depend on the data output precision, i.e. 32bit data or 16bit data output. By utilizing 4 CAN message with 16bit sensor data precision, the sensor can output a maximum of 16 different sensor data for a given instance.

CAN channel mapping (16bit data output)

CANOpen ID	Sequential CAN	Output data
181h	515h	channel 1	channel 2	channel 3	channel 4
281h	516h	channel 5	channel 6	channel 7	channel 8
381h	517h	channel 9	channel 10	channel 11	channel 12
481h	518h	channel 13	channel 14	channel 15	channel 16
701h	-	(heartbeat)

CAN channel mapping (32bit data output)

CANOpen ID	Sequential CAN	Output data
181h	515h	channel 1	channel 2
281h	516h	channel 3	channel 4
381h	517h	channel 5	channel 6
481h	518h	channel 7	channel 8
701h	-	(heartbeat)

CAN Mapping

Each channel can be assigned different sensor data by changing the CAN mapping via LpmsControl2. The table below summarizes the available sensor output data.

Mapping index	Data	Unit	16bit data scaling factor
0	Not assigned
1	Raw Accelerometer X	g	1000
2	Raw Accelerometer Y	g	1000
3	Raw Accelerometer Z	g	1000
4	Calibrated Accelerometer X	g	1000
5	Calibrated Accelerometer Y	g	1000
6	Calibrated Accelerometer Z	g	1000
7	Raw GyroI X	Not available
8	Raw GyroI Y	Not available
9	Raw GyroI Z	Not available
10	Raw GyroII X	dps or rad/s	10 (dps), 100 (rad/s)
11	Raw GyroII Y	dps or rad/s	10 (dps), 100 (rad/s)
12	Raw GyroII Z	dps or rad/s	10 (dps), 100 (rad/s)
13	Bias calibrated GyroI X	Not available
14	Bias calibrated GyroI Y	Not available
15	Bias calibrated GyroI Z	Not available
16	Bias calibrated GyroII X	dps or rad/s	10 (dps), 100 (rad/s)
17	Bias calibrated GyroII Y	dps or rad/s	10 (dps), 100 (rad/s)
18	Bias calibrated GyroII Z	dps or rad/s	10 (dps), 100 (rad/s)
19	Alignment calibrated GyroI X	Not available
20	Alignment calibrated GyroI Y	Not available
21	Alignment calibrated GyroI Z	Not available
22	Alignment calibrated GyroII X	dps or rad/s	10 (dps), 100 (rad/s)
23	Alignment calibrated GyroII Y	dps or rad/s	10 (dps), 100 (rad/s)
24	Alignment calibrated GyroII Z	dps or rad/s	10 (dps), 100 (rad/s)
25	Raw magnetometer X	uT	100
26	Raw magnetometer Y	uT	100
27	Raw magnetometer Z	uT	100
28	Calibrated magnetometer X	uT	100
29	Calibrated magnetometer Y	uT	100
30	Calibrated magnetometer Z	uT	100
31	Angular Velocity X	dps or rad/s	10 (dps), 100 (rad/s)
32	Angular Velocity Y	dps or rad/s	10 (dps), 100 (rad/s)
33	Angular Velocity Z	dps or rad/s	10 (dps), 100 (rad/s)
34	Quaternion W		10000
35	Quaternion X		10000
36	Quaternion Y		10000
37	Quaternion Z		10000
38	Euler X	deg or rad	100 (deg), 10000 (rad)
39	Euler X	deg or rad	100 (deg), 10000 (rad)
40	Euler Z	deg or rad	100 (deg), 10000 (rad)
41	Linear Acceleration X	g	1000
42	Linear Acceleration Y	g	1000
43	Linear Acceleration Z	g	1000
44	Pressure	kPa	100
45	Temperature	°C	100

Example

Assuming default sensor settings, the CAN bus settings and corresponding data output are shown below:

Here we can decode the data for CAN-ID 181h as follow:

181h	Byte [0:1]	Byte [2:3]	Byte [4:5]	Byte [6:7]

181h	Byte [0:1]	Byte [2:3]	Byte [4:5]	Byte [6:7]
Byte	22 FF	39 00	C9 03	FA FF
Integer value	-222	57	969	-6
Corresponding data	Acc Calibrated X	Acc Calibrated Y	Acc Calibrated Z	GyroII Align. Calibrated X
Scaled data	-0.222g	-0.057g	0.969g	-0.6dps

Like wise, the raw data can be decoded for 281h, 381h, 481h as follow:

281h	Byte [0:1]	Byte [2:3]	Byte [4:5]	Byte [6:7]

281h	Byte [0:1]	Byte [2:3]	Byte [4:5]	Byte [6:7]
Byte	FF FF	00 00	75 07	75 09
Integer value	-1	1	1909	2421
Corresponding data	GyroII Align. Calibrated Y	GyroII Align. Calibrated Z	Mag Calibrated X	Mag Calibrated Y
Scaled data	-0.1dps	0.1dps	19.09uT	24.21uT

381h	Byte [0:1]	Byte [2:3]	Byte [4:5]	Byte [6:7]

381h	Byte [0:1]	Byte [2:3]	Byte [4:5]	Byte [6:7]
Byte	DD 02	4F 01	0D 05	73 FB
Integer value	733	335	1293	-1165
Corresponding data	Mag Calibrated Z	Euler X	Euler Y	Euler Z
Scaled data	7.33uT	3.35deg	12.93deg	-11.65deg

481h	Byte [0:1]	Byte [2:3]	Byte [4:5]	Byte [6:7]

481h	Byte [0:1]	Byte [2:3]	Byte [4:5]	Byte [6:7]
Byte	96 26	93 01	42 04	EF FB
Integer value	9878	403	1090	-1041
Corresponding data	Quat W	Quat X	Quat Y	Quat Z
Scaled data	0.9878	0.0403	0.109	-0.1041