HVFE CAN specs

Specifications for the CAN Bus messages used by the Remote High Voltage Front End

These are the CAN messages that are sent or may be sent by the Remote High Voltage Front End, and the ones that it listens to.

Notes:

• Period: 2 messages every 100 ms, separated by 10 ms
• Length: 3 bytes

ID	Bytes	Byte 0	Byte 1	Byte 2	Byte 3	Byte 4
681h	5	Load current (1)		Source current (1)		Data (2)

1. [10 mA], + = into battery, big-endian
2. Bit 0: no voltage seen by the HVFE during contactor tests

Notes:

• Maximum period: 300 ms (after which it assumes there is no such message on the CAN bus)

ID	Byte 0: Address	Byte 1: Mask	Byte 2: Data
			Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
680h	48h	FFh	-	Drive Precharge switch	Drive SW- switch	Drive SW+ switch	Drive relay K3	Drive relay K2	Drive relay K1	Fault

The Remote HVFE and the BMS controller are programmed at the factory to work with each other.

If you need to change the the CAN Bus speed, or ID of the messages used (because of a conflict with messages from another device on the bus), you my reprogram both the Remote HVFE and the BMS controller, to new values.

Three items are programmable through the CAN bus:

• The CAN bus speed (125, 250 or 500 kHz)
• The CAN ID of the received control message
• The CAN ID of the transmitted status message

The EEPROM may also be programmed through the ICSP connector and a PIC programmer.

The control message (by default at ID of 680h) is also used by the Elithion display. If you are using an Elithion display, changing this ID will make the display unoperable (the display cannot be reprogrammed).

Procedure:

1. Connect to the board through the CAN bus, using the CAN bus speed that the board is presently set to
2. Send CAN messages to modify the EEPROM
3. Power down and up for the changes to take effect

ID	Length	Byte 2: Data
		Data 0	Data 1	Data 2	Data 3	Data 4	Data 5	Data 6	Data 7
7FFh	8	12h	34h	56h	78h	9Ah	BCh	EEPROM address	EEPROM data

Item	EEPROM Address	EEPROM Data	Default
high byte of the CAN ID of the received control message	00h	00h to 07h	06h
low byte ""	01h	00h to FFh	80h
high byte of the CAN ID of the transmitted status message	02h	00h to 07h	06h
low byte ""	03h	00h to FFh	81h
CAN bus speed code	04h	00h for 500 kHz 01h for 250 kHz 03h for 125 kHz	00h
Status message rate	05h	rate [10 ms]	100 (= 1 Hz)

Notes:

• Wait 10 ms minimum before programming a new value
• The value for the CAN Bus speed is validated, so there's no risk of locking the board from being programmed by CAN bus