AVGO AVG 938

[Tomi8609]

Hello

I really like this project!
How do you generate the ACC signal for the aftermarket head unit?
I have an Opel specific head unit that was originally made for Corsa D, but unfortunately I don't have the canbus decoder, so I would like to use your project for that.
I have bought two decoders but none of them communicate with the steering knobs, I can't get the hidden menu and the BC to work with either.

[adamczykpiotr]

Hey, I really don't think this project generates ACC voltage since both stereo and the board I've made for this project were lowered by ignition voltage.

You could easily adapt it to be a can bus decoder but there a few tricks with Can & Corsa. First of all, you have to make sure you're attaching to correct can network since button presses are transmitted on booth SW-CAN (single wire = CAN-H + GND; running at 33.3kbps which isn't supposed by all decoders) and MS-CAN (95kbps).

If you're trying to set everything thing up without a car, remember to attach 120 OHM termination resistors on both ends of can wiring.

[adamczykpiotr]

From what I remember, this project was made to work with MS-CAN but if you're trying to figure out SW-CAN button presses, this might be useful as well: https://github.com/JJToB/Car-CAN-Message-DB/blob/master/Opel/Astra/H/LS-CAN/175_SteeringWheelButtons.md

[Tomi8609]

Thank you for your reply.
I believe that they are on two separate can-buses, but there is another project that I have already done and there is also MS-Can in use and the steering wheel buttons work, but unfortunately it only works when using the factory head unit.

https://github.com/PNKP237/EHU32

[Tomi8609]

Almost all canbus decoders as far as I know have a UART (TX/RX) output which has to be connected to the head unit.
For this connection it is important that the data rate is the same.
How can I find out what data rate is set on my head unit and canbus box? Is there any way to change this?

[adamczykpiotr]

Thank you for your reply. I believe that they are on two separate can-buses, but there is another project that I have already done and there is also MS-Can in use and the steering wheel buttons work, but unfortunately it only works when using the factory head unit.

https://github.com/PNKP237/EHU32

This might be because EHU has the Can termination resistors inside, I'd suggest hooking up 120 ohm to MS-CAN and seeing for yourself if you're getting data packets after that.

You could do that easily if you have a oscilloscope, then you could just measure it precisely. Without it I think you can only try each combination and hope for the best

[adamczykpiotr]

One more thing, remember that STM32F103 has memory region shared for CAN and HW UART so if you decide to log something using this code, CAN might suddenly stop working

[Tomi8609]

Thanks for the reply, unfortunately I don't have an oscilloscope so I can't test this

[Tomi8609]

Hello

I was looking at the schematic and my question is: don't you have to connect a VCC with 10k resistor at the handbrake part?

You wrote that you could extend this project to generate an ACC signal.
Can you help me with this?
I was thinking mainly about modifying the program.

[adamczykpiotr]

Hey!
I might be mistaken but if I recall correctly the parking brake sensor is left floating (BCM has a pull-up resistor) and BCM senses only when it's pulled to ground thus there's no need for pull-up in this design

[adamczykpiotr]

If you'd like to implement ACC logic I'd suggest simply copying "Reverse" section and then inverting the logic on the output so it produces +12v instead of GND. I don't really remember which CAN frame is responsible for notifying bus of a ignition being turned on but if your aim is to simply power up radio as soon as key is inserted, listening for frame with id 0x100 (bus wake-up) might be your best bet

[Tomi8609]

Maybe I'm looking at the drawing wrong but the Day/Night toggle and the Reverse part of the output is not +VCC?

[adamczykpiotr]

This connection diagram was made quite some time ago before I knew how to do it properly ;)

In this case VCC is +12v; +5v and 3V3 rails are marked correctly