OEM Steering Wheel Controls Input Jack

There are several threads on this topic on various discussion boards, but none of them seem to offer much valuable information...

Many aftermarket head units come equipped with an input connector for "OEM steering wheel controls". You buy an adapter from the HU manufacturer or from an independent company like PAC-Audio, connect it to the head unit and to the steering wheel and voila.

The problem is that
1) the adapters only work for specific cars and head units
2) they are not very cheap

Does anyone know what the input jack's communication protocol is? Is it digital or resistor-based? I know that the steering wheel controls are resistor-based most of the time, but what about the input jack?

In my case the HU is Clarion DXZ389RUSB. The input jack protocol should be very similar to that of Kenwood, JVC and Alpine, because a single SWI-Jack adapter should work on all of them.

I measured the output of the jack's three pins and found that two of the pins are connected to GND and the third one has +3V voltage. I connected a potentiometer between the high pin and the ground pin, but various resistances didn't have any effect at all (not that I expected any..)

Does anyone know anything about the input jack? Is anyone with a head unit (preferably Clarion/Kenwood/JVC/Alpine) and an adapter willing to measure the output of the adapter and see what happens when he presses a button?

My steering wheel controls are custom, so an adapter is not even an option for me, but even if it were, I think it is time to finally reverse-enginner the input jack.

Any help would be very appreciated, thank you.

Most these days are CAN or a variant, the only people who can help are the manufacturers such as Clarion or armour audio UK.

Most signals from the steering wheel controls these days are CAN or similar, but do you think that the head unit input also expects digital signals?
This is the part I am interested in - the head unit's input, not the car's output.

They are resistor based.  Jvc Alpine Clarion and Kenwood use the same specs.  Hence the Pac-audio.com SWI-JACK  Steering wheel Interface for JVC Alpine Clarion and Kenwood.  Sony and Pioneer are different.  Sony offers a stand alone joystick type remote that has only switches and resistors on the circuit board.  No microprocessor or even a transistor on the board.  It is a simple voltage divider resistor network.

"i am an idiot" if you are sure about this then this is something I could not find googling for about three weeks.
You don't by any chance know the exact values of the resistors, do you?

I don't an EDIT button, so..

I found values for Sony and for some OEM steering wheels, but there don't seem to be values for the JVC/Clarion/Alpine/Kenwood radios anywhere. I find this interesting (and disturbing) given that most car electronics enthusiasts seem to use Alpine head units..

SWI JACK on Ebay for 40 bucks. Not much for the simplicity the product will give you...

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Mike M2
Tech Manager
CS Dealer Services

Mike M2 wrote:

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SWI JACK on Ebay for 40 bucks. Not much for the simplicity the product will give you...

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see my first post: "My steering wheel controls are custom, so an adapter is not even an option for me, but even if it were, I think it is time to finally reverse-enginner the input jack. "

I have no idea of the value, my dad has one mounted on his scooter.  I will see what I can find out for you this weekend. 

There aren't specific resistor values I have done a few nissans and just used varying resistor values in between the range that they give you. All that matters is how it is programmed

chadwa2003 wrote:

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There aren't specific resistor values I have done a few nissans and just used varying resistor values in between the range that they give you. All that matters is how it is programmed

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He is not able to use an SWI piece, he has buttons that he has or is building himself. There is a specific resistor value that the Sony joystick remote uses as a voltage divider network.

Exactly.
If you could really measure the values, that would be great, thank you.

It will be Tomorrow or Monday before I can get you that info. 

Thanks. I have found a guy who makes these adapters and sells them for money (a lot less than SWI-JACK and such), he claims that the adapter works for Alpine, JVC and some other models, but he has not tested Clarion yet.
He posted a schema in one discussion and he uses a Motorola microcontroller https://pavel.lajsner.sweb.cz/swc/swc-kx8.sch.png
I am beginning to worry there will be more to it than just resistances..

New info again - https://www.avforums.com/forums/portable-dvd-media-players-recorders/248455-jvc-stalk-adapter-diy-2.html

If JVCs are controlled digitally, there is a strong possibility that Alpine and Clarion will also be.