CAN Communications.

[MWPau]

Im working away on my own dash display too.

At the moment im dumping the can transmissions between the MS3 and the TinyIOx.
Ive worked to how to format the header bytes, but the request data bytes are puzzling me.

An example of my can messages dump:
00->04 = msg_type:MSG_REQ var_blk:07 var_offset:0002 data(hex): 07 40 08
00->04 = msg_type:MSG_REQ var_blk:07 var_offset:0010 data(hex): 07 41 08
04->00 = msg_type:MSG_RSP var_blk:07 var_offset:0512 data(hex): 03 FF 03 FF 03 FF 03 FF
04->00 = msg_type:MSG_RSP var_blk:07 var_offset:0520 data(hex): 03 FF 03 FF 01 2C 01 2A

So, in the first request the data bytes are 07 40 08.
07 = myvarblk
40 08 = somehow is length & offset?

I gather the 8 is length, so that makes 40 0 the offset but shifted left by 1 bit?

IMO, the can_tech doc is too MS internals orientated.
cx_myvarblk, cx_myvaroff, cx_varbyt, etc dont actually specify where that data is located in a normal CAN message (ie, xx bits of the first data byte).

[jsmcortina]

IMO, the can_tech doc is too MS internals orientated.
cx_myvarblk, cx_myvaroff, cx_varbyt, etc dont actually specify where that data is located in a normal CAN message (ie, xx bits of the first data byte).

It does, there's a diagram just under the words
"The 29 bit CAN message header is divided into blocks across four 8-bit registers"

James

[MWPau]

Yes, there is that nice table for the CAN header.
Something similar would be great for the format of the 3 data bytes of a MSG_REQ packet.
That's what I'm having trouble working out.

Thanks

[jsmcortina]

Yes, there is that nice table for the CAN header.
Something similar would be great for the format of the 3 data bytes of a MSG_REQ packet.
That's what I'm having trouble working out.

Thanks

I updated the http://www.msextra.com/doc/ms3/can_tech.html page with some more information.

James

[MWPau]

Brilliant.
Thanks very much for that James

[dll67]

http://www.msextra.com/doc/ms3/can_tech.html

Anyone know if this page still exists?
The link is broken

[24c]

It is, but have you seen this page?
http://www.msextra.com/doc/pdf/Megasqui ... adcast.pdf

Mike

[MWPau]

Where did you find that ^^ ?
These docs locations changes are frustrating

[24c]

Actually, it's quite easy!

site_not_found.png

Go to the Manuals Index link and both CAN updates are at the bottom of the page.

Frustrating maybe, but the files have been updated recently, and I personally think stuff is getting much easier to find and is better organised than before, so I'd bookmark that link.

Mike

[MWPau]

Ah so it is
I only kept this page bookmarked, so missed it: http://www.msextra.com/manuals/ms3manuals/