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car-radio/notes/keep-wake.txt

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+https://www.electro-tech-online.com/threads/ford-canbus-modules-wake-up.158834/
+
+It seems like there is a circle of messages that happen for things to have safe messaging.
+
+"
+So any message at all will wake the module, but it may then go to sleep if there are no sleep/wake messages, only to be woken again a moment later. 
+
+What happens is that all the modules that form a "ring" with each module transmitting 100 ms after the previous one. The first byte of each message is the ID of the next module in the ring, without the 0x5 at the start. The IDs go up in order, so if you have three modules, the sleep wake messages might be like this:-
+
+0x525 33 12
+0x533 37 12
+0x537 25 02
+"
+
+Currently, decode.py waits for 55D, meaning the FCIM is saying "55D go". So we send 50C 0C 12 00
+
+"
+ The 2nd byte has a 1 in the first nibble when the module is ready to sleep, and a 0 when it needs the CANbus to be awake. So in this case the module transmitting 0x537 needs the CANbus awake. The 2nd nibble of the 2nd byte is 1 when the module is working, and 2 when the ring is stable. As the car wakes up, the different modules work out the order of the ring, and it's a bit chaotic for a couple of seconds, but if they all follow the rules, it all sorts itself out in a few seconds.
+"
+
+So if we change 0C 12 to 0C 02, will we get permanent wake?
+
+Yes that works.