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.

Sent 7 ms after each time a message is received from the BMS controller.

If no messages are received from the BMS controller, sent at a configurable rate (10 ms to 2.55 s, 1 s default).

Rev 1.03 and above

ID	Bytes	Byte 0	Byte 1	Byte 2	Byte 3	Byte 4	Byte 5	Byte 6
681h	7	Load current (1)		Source current (1)		Data (2)	Pack voltage (3)

Rev 1.02 and below

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. The value is refreshed 1/s, regardless of the message rate
2. Normally 01h. Bit 0: 1 = no voltage seen by the HVFE during contactor tests isolation is OK
3. [100 mV] (Resolution is 1.2 V)

Notes:

• Maximum period: 2 s (after 3 s 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, 500 kbps or 1 Mbps)
• 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 (either through a computer and a CAN adapter, or using the "Custom Output Message" feature of the BMS)
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	Notes
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	FFh, 00h, 01h or 03h	00h	1
Status message rate	05h	01h to FFh	100	2
High byte of the offset in the high current sensor (load current)	06h	00h	00h	3
Low byte ""	07h	00h	00h
High byte of the offset in the low current sensor (source current)	08h	00h	00h
Low byte ""	09h	00h	00h
CAN bus receive timing code	0Ah	00h to FFh	F7h	4

Notes:

• Wait 10 ms before programming a new value

1. The value for the CAN Bus speed is validated, so there's no risk of locking the board from being programmed by CAN bus
   • FFh for 1 Mbps {Rev 1.07 and up}
   • 00h for 500 kbps
   • 01h for 250 kbps
   • 03h for 125 kbps
2. Normally, the HVFE only transmits as a response to a received message.
   If the HVFE includes current sensors, it also transmits on its own, at a rate set by this setting. Units: [10 ms]. For example: 1 = 10 ms; 10 = 100 ms; 100 = 1 s...
3. {Rev 1.06 and up}. Units: [10 mA] 0000h = 0 A offset; 0001h = decrease the reported value by 10 mA; FFFFh = increase the reported value by 10 mA
4. {Rev 1.08 and up}. See the CAN Rx Timing page

Example: configure the HVFE from 500 kbps to 250 kbps using a custom message

1. Start with both the BMS master and the HVFE at 500 kbps (factory default)
2. In the GUI, go to the Configure/Communicate tab
3. Set the "Custom message" parameters as shown below
   • ID is "7FF", per the table above
   • Number of bytes is 8
   • "Item" = 8 means "constant"
   • "Multiplier" and "Divider" don't matter: set them to 1
   • "Offset" is the value to be sent for that byte
     • Bytes 0~5 are 0x12 through 0xBC, converted to 12 through 188 decimal, per the table above
     • Byte 6 is set to "4" for CAN speed
     • Byte 7 is set to "1" for 250 kbps
   • You can use this configuration file
4. Click the "Write to BMS" button; the BMS will send the custom message once a second; the HVFE will configure its speed to 250 kbps
5. Change the "ID" to 0 to stop the custom messsage; change the "Rate" control to 250 k b/s
6. Click the "Write to BMS" button; the BMS will stop sending the custom message; the BMS master will configure its speed to 250 kbps but will keep on using 500 kbps for now
7. Remove power to the unit; this will reset both the BMS master and the HVFE
8. Power the unit back up; both the BMS master and the HVFE will use their newly configured speed and operate at 250 kbps