Bit numbering

[gtihk]

I use Can Capture to read and analyse OE CAN messages.The Byte and Bit numbering seems to be different from what M1 uses. I am working on a BMW which uses Little Endian.
If I want to assign the left 2 bytes for a channel, what start bit should I use please?
These two bytes might be called Byte 7 and 6 in Little Endian.
Any help will be appreciated.

[rntechnologies]

Hi Githk,
Your question is a little vague.
Firstly, the M1 is quite capable of handling either type of CAN messaging (RX and TX), just by setting the endianness flag in the CAN message.
Have a look at the below image to assist with Byte numbering within a CAN message:

Endianness.jpg (33.39 KiB) Viewed 27562 times

Hopefully this helps understand how the numbering works.

[gtihk]

I am a little confused.
I was given this by MoTec.

endian.png (64.92 KiB) Viewed 27549 times

[rntechnologies]

Hi githk,
These images show the exact same thing

[Stephen Dean]

Hi Ryan,

They are different...

[rntechnologies]

My apologies!
I didn't read that very well!

[gtihk]

If I want to assign Byte7 and Byte 6 as a received channel,what Start bit should I use please? Would it be 0 or 7?

[David Ferguson]

You can try 0, but I think that byte6/7 whould start at bit 48 with length 16.

[gtihk]

I think for big endian, Byte 6/7 should start with bit 48.
I was not sure about little endian. This was why I was asking.