VCS TransmitCompound CAN massages protocol

[daw]

Hello. I am using C185 display. I want to use it's CAN output and log it with a different logger.
I set VCS TransmitCompound full as a CAN protocol that I want to transmit from C185. It uses CAN ID: 0x01F.

I set it in MoTeC C185 Dash Manager in Connections->Communications->CAN 1.

Can somebody provide this protocol description, the best in a DBC file form. Or at least in a table with properly described channels.

Maybe there is a link to a document that describes that, but I searched everywhere and didn't find any.

Thank you in advance.

[Stephen Dean]

Hi,

That CAN Transmit Template is probably not the best option to use for this as it is designed to provide data into our camera systems, you would be better off developing a custom transmit template out of the Dash that has the channels and addresses that you need.

[daw]

Thank you for your answer. Unfortunately I'm limited in this matter.
The C185 is built it Lamborghini Super Trofeo and has one CAN logger output socket that is connected to a dash and configured with this protocol.
A team cannot modify the output, and we have to log data from the car as it is delivered. We are not part of a team.
So is there anywhere a description of this VCS TranmitCompound CAN protocol? The best in a DBC file.

[David Ferguson]

All the info is in the CAN template. Create a C185 config, add a VCS Transmit Compound CAN template, then edit it. All the info you need is in there.

[daw]

OK. So I went through the configuration in C185 Dash Manager, created CAN protocol, connected to a car and:
- throttle is working fine,
- RPMs are working fine,
- brake shows 0 or 1 - so it probably should not be divided by 100.

Steering angle is not changing.

I attached a screenshot with a configuration. Could you please clarify how to interpret Identifiers settings, its offset, ID and ID Mask?

What I do in handling of messages: I check if in a massage with id=0x01F the first two bits are equal to 00 to read speed, RPMs and gear, or equal to 01 to read throttle, brake and steering angle values.
Is that correct?
This identifiers table is not clear and there is no documentation about it.

[David Ferguson]

Ask your MoTeC dealer for help. The documentation for CAN communications is in Dealer Tech Note 19. The relevant section says:

Message Type
Single: With single message type, the position of each byte in the data string relates to the channel
assigned.
Compound: With compound message type there is a message identifier within the data section of the
message or packet. The value of the ID relates the rest of the data to a unique set of channels. This
message type allows for communicating a large number of channels on a single CAN address. When
transmitting a compound message the Transmit Rate is the rate at which each message is transmitted,
meaning each channel is transmitted at the Transmit Rate divided by the number of ID sets.
Compound Settings
Offset: The number of bytes after the header or CAN address where the most significant byte of the ID
is located in the data.
ID: The value of the identifier in hex.
ID Mask: A bit mask for the ID. (See Bit Masking). Has no effect on transmit message.

example compound message

Compound message example.jpg (71.04 KiB) Viewed 6702 times

When transmitting a compound message the data is written to the message after the ID. Data can
therefore be written over the ID. Care must be taken not to do this, which is as easy as not transmitting
data on the same offset as the ID.
Often a two byte identifier is not needed. In this case, one of the two bytes can be overwritten with data.
This will work as long as there is still at least one identifying marker in one byte with the receiving end
configured to read only this byte.
Alignment settings do not affect the identifier; it is always transmitted as Normal - most significant byte
first.