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June 10, 2023, 01:21:23 01:21


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Author Topic: Android car radio CAN module  (Read 273 times)
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anotherandrew
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« on: May 25, 2023, 09:20:38 21:20 »

Hello friends. Many chinese android car radios have a optional small box that connects to car CAN bus and gives simple serial UART to this radio. example is https://www.aliexpress.com/item/1005002569086079.html.

I can see UART protocol and there is some detail. example

2E 20 02 01 01 DB or 2E 20 02 02 01 DA

for volume up and down. The base protocol format, checksum and etc is understood, but there is lots of messages that I cannot find detail for.

Does someone have full protocol for these? I see some reverse of java android apk on xda-devs and github which detail some but not all.
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yahoo
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« Reply #1 on: May 26, 2023, 12:05:06 00:05 »

If you just need to use the steering wheel keys, there is no need to use the CAN bus decoder at all. All these car radios have KEY1 and KEY2 lines on the black power connector and you can connect the analog key wires directly and then to teach the radio for each key what is the resistor value.
First I did it like that and it worked. But unfortunately for my RAV4 there were 3 key lines and the radio support only 2 lines. So, finally I bought CAN decoder. In fact, there is nothing to do with the CAN bus, just KEY1, KEY2 and KEY3 are connected as wires to this CAN decoder and it scans the keys and create serial packets for each key press and release.
The real CAN bus information is related to the door switches, A/C control, etc., which is not really needed.
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anotherandrew
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« Reply #2 on: May 26, 2023, 01:01:56 01:01 »

thank you but no, I want to know if I can send arbitrary can messages. I have the vw tdi vehicle (b7 body, 2015 passat model year) with dynaudio factory amplifier. it can only be power on and off by CAN. I sniff and see the messages (and volume up down and so on) and can make it power on now, but would like to control with custom android app through gateway. I ask chinese vendors but nobody wants to help so I hope maybe peopel here have some document.

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yahoo
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« Reply #3 on: May 26, 2023, 01:33:41 01:33 »

From the CAN bus side you will find many information for the packets used in each car model. But from the UART side each decoder box uses unique serial protocol and when you connect one can bus decoder you have to setup the car radio which manufacture is the decoder, and which model from this manufacture. I see about 30 manufactures with 10-30 models each. They are not equal as protocol so it will be hard to find exactly the protocol for your decoder box.
I started the other way. I bought one universal decoder with bluetooth interface, well documented, and with many phone software for it, so I can make whatever I need, no need to reverse engineer anything:
https://vi.aliexpress.com/item/1005001287644836.html
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anotherandrew
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« Reply #4 on: May 26, 2023, 03:22:21 03:22 »

I have device like thsi too; unfortunately what I am searching this does not work as infotainment CAN does not appear on OBD port, or at least I am not able to convince the OBD gateway to forward infotainment to OBD for bluetooth scanner to see.

I have CAN commands to turn on and off amp and adjust volume. I was hoping I could make the android radio send UART command to this chinese "Raise" CAN module. this is why I seek that UART protocol. Right now I have atmega and spi CAN module which controls dynaudio amp, but it is not as slick as I want. Thank you for this information, it is nice to see others doing similar things. :-)
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« Reply #5 on: May 26, 2023, 12:12:22 12:12 »

I'm not really interested by this subject. My second Chinese car radio stopped working after another cold winter here. So, I decided to buy another one cheap radio without CAN decoder and the more complex wiring set, expecting they are universal and I can attach my old CAN decoder box to the new radio. No, they are not the same and my old box was not in the list of supported manufactures and models. So, I had to buy a new one from a manufacture and model seen in the setup list in the radio menu.
You mention Raise, this appear to be more popular brand at the moment and the connector pinout is shown on the attached picture (valid at least for the Toyota models). You can see that in addition to the CAN bus, the decoder is controlling the reverse camera voltage, reads the steering wheel keys and add special protocol commands for them in addition to the decoded CAN bus packets.
If you have a logic analyzer, you can scan the CAN bus and the decoder output at the same time, and to see the relation between the CAN packets and the UART data. For CAN, there is enough information for the data, so one by one you will see how they are decoded. For the reverse direction you will need a car radio with a proper setup for this decoder box and to try to control the AC functions or something else and to see the UART commands to the decoder. I postponed that exercise for later when I have time. I really don't need it when almost everything is controlled by my radio. And with the addition to the bluetooth adapter, I have access to all service information and sensors inside the car, to read the trouble codes way before they appear, etc.
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