Re: Custom CDC to SID text

Posted by Ziq on Aug 18, 2017; 6:31pm
URL: http://bluesaab-forum.90.s1.nabble.com/Custom-CDC-to-SID-text-tp90p1185.html

Just a note here, my IHU (nav unit)  sends a message that it does not want to display anything every second. Upon seeing this message I immediately send a message pretending to be the same node but that i want to send something. I am then granted write permission and can write what I want. I have a short flicker once every five minutes or so but that I contribute to slow response of my microcontroller due to the lack of a interrupt implementation. If the ACC acts the same as my IHU i imagane it's free to highjack that empty space as well. It's been working fine for me fir18 months now... 

/Petter 

Den 18 aug. 2017 18:51 skrev "Karlis [via BlueSaab Forum]" <[hidden email]>:

Timpa wrote

Thanks, if  I understand it correct
You send a request from "SPA" to SID 0x357 (0x1F=request,0x02=row2, byte3 priority?)

Yes: 0x1F=requesting node ID (SPA), 0x02=row2, byte3=message type (0x03=driver action)

Timpa wrote

and get a okay from SID 0x368 (byte 0=0x02(row2) and byte 1=0x12(SPA)).

Correct...

Timpa wrote

Then you send 3 lines with Text to SID from "SPA" 0x337.

Yes. These three frames include message sequence, type (sent on an event or basetime), address of the SID and 5 x bytes of an actual text. Note that everything larger than 12 chars of the text will be zeroed out as that's all SID can display on a single line.

Timpa wrote

Hope I have get the principle right

Yes, you got the idea right.

Timpa wrote

Have you tried to use ACC instead of SPA ? ACC only uses SID when you make
some changes or calibrate.

This can be done on behalf of any node on the car. The trick is to find and pick one that's not installed. The thing is that when a node is not interested in writing on SID, it has to send out a specific frame telling so. Then, when node is interested in writing on the SID, it starts asking for a grant to write. The SID then decides who and when can write. So even if ACC is used, you could, theoretically, send a request to write, but then the "Actual" ACC will also push out a frame saying that it doesn't want to write. So SID will be confused receiving two frames, supposedly from the same node with confusing requests. This can lead to all sorts of problems. From flickering text to SID going dark and the need to pull the fuse...

On my and Seth's car there's no SPA, so we have all the necessary means to pretend to be one and everyone else on the bus are happy as our requests/text sending don't interfere with anything else.

Good luck!

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