How to read/write drive parameter over CAN bus

In this example, we will read/write the parameter /driver/limiter/ppos. This parameter has ID 80 (0x50). And we will write the value 1000.0 to it and then read it back.

What do you need to prepare before:

• The controller is turned ON
• CANbus works properly
• The controller CAN address is set to 0

note

• All the values are in big-endian

Step 1: Compose the CAN frame to write a parameter

note

• A list of available parameters can be found here
• Always check the parameter type. Most of them are float, but some integers are also used.

CAN ID	DLC
0x0C7	8

Byte 0	Byte 1	Byte 2	Byte 3	Byte 4	Byte 5	Byte 6	Byte 7
Receiver address 0x0	Write parameter 0x3	Parameter ID 0x50	Array index 0x0	Float LSB 0x00	Float 0x00	Float 0x7A	Float MSB 0x44

note

• How to compute CAN ID: SID is 24, sender address is 7 -> (24 « 3) + 7 = 192 + 7 = 199 (DEC) = 0xC7
• Dec 1000.0 is in float 0x447a0000

Step 2: Receive a response

CAN ID	DLC
0x0C0	6

Byte 0	Byte 1	Byte 2	Byte 3	Byte 4 - Byte 5
Receiver address 0x7	Write parameter response 0x43	Parameter ID 0x50	0xFF = error Parameter ID if success	Error code (INT16)

Step 3: Read back the parameter

CAN ID	DLC
0x0C7	8

Byte 0	Byte 1	Byte 2	Byte 3	Byte 4 - Byte 7
Receiver address 0x0	Read parameter 0x2	Parameter ID 0x50	Array index 0x0	0x0

Step 4: Receive a response with parameter value

CAN ID	DLC
0x0C0	5-8 Depend on parameter type

Byte 0	Byte 1	Byte 2	Byte 3	Byte 4 - Byte 5
Receiver address 0x7	Read parameter response 0x42	Parameter ID 0x50	0xFF = error Parameter ID if success	Parameter value - 0x00007A44 Error code (INT16) in case of error

Error code

Error code	Description
-1	Parameter ID out of bound
-2	Parameter not found
-3	Variable is not parameter
-4	Set value is below minimum
-5	Set value is above maximum
-6	Parameter is preset type and value is not in the list