I think that we need to create a common repository/wiki database where we can share reverse engineered car information with a common standard, aiming at being able to automatically download a “descriptor” file that can run on an universal software.
This is not as hard as it seems; most of the data is usually extracted as the raw number, multiplied by a number, plus an offset. More complex formulas are not very common but exist and will be handled accordingly.
So, for every car, we have a page that states pinouts, bus speed, misc notes, and all the found messages. Log files can be shared and will be available for anyone to study.
Car: Renault Twizy
Bus speed: 500Kbps
– OBD connector
— Pin 6: CAN H
— Pin 14: CAN L
Battery pack temperature,0x55, 8,1000ms
Single cell voltage 1-5,0×556,8,100ms
0x155 BMS status (10ms)
|Byte 0||Byte 1||Byte 2||Byte 3||Byte 4||Byte 5||Byte 6||Byte 7|
|PWRH PWRL||Battery power||–||0x0F00||(0x7D0-(n&0x0FFF))*16||kW|
|Instantaneous battery power measured from the BMS. A negative value indicates charging, either due to regenerative braking or AC charging connection. This value can be used in conjunction with BV (0x55F) to calculate current flow. The indicated power is the total coming from the battery, power consumed by auxiliary devices is not separated from the traction power.
Example: (0x7D0-(0x97FF&0x0FFF))*16 = -752W (charging)
|BMS unit status.
· 0x94 = Initialization in progress; data acquired may not be valid
· 0x54 = BMS ready
|Battery state of charge.
Example: 0x6BF0/400 = 69.06%
This is just a brief example; the table may need more columns (to define if the message is read only or if we can send it to activate stuff, a method to handle bitmapped statuses, etc.) but it’s just to explain the idea. There will be a standard way to describe requests and responses, and how to handle data spanning multiple messages.
The community will help to converge to a standard way to save log files, develop tools to convert them, study their content and publish results. I have a small collection of softwares I’ve written in these years that I will make available with an open source license. Other options are:
OVMS CAN-RE-tool https://github.com/openvehicles/CAN-RE-Tool