JVC stalk adapter - DIY?

[pleriche]

I recently bought one of the last of the Rover 25s available new, which came with a dealer-fitter JVC KD-G152 - no stalk control and no CD/MP3.

I've almost decided to upgrade to a JVC KD-G612. Stalk adapter would add £30, assuming I can find the right one. But it strikes me, it should be easy to DIY it.

I suspect the stalk control input on the JVC is simply a 3.5mm stereo jack socket (easy to obtain a plug, if I haven't already got one).

First question: am I right?

The loom has a rectangular multicolour block connector hanging loose, with 20 pin positions but only 2 used. These must be the stalk controls, each of which probably switches between +12v and ground for "up" and "down". (Will check with a test meter when I get the chance.) Since I learnt to solder some 45 years ago, taking the 2 wires which go into the multicolor connector into a stereo jack plug seems less than challenging.

Second question: is there a flaw in my logic somewhere?

Thanks - Philip

[pleriche]

The Haynes manual confirms that the two wires (pink and white) going into the multicolour block are the stalk controls. So I connected a test meter (20v range) between each of these and earth, and between each and +12v, each time waggling each of the stalk controls controls both ways. Not so much as a flicker from the test meter. So if the stalk controls don't switch the wires to either ground or +12v, what do they do? Haynes' circuit diagram simply shows 2 single pole switches to ground.

Meanwhile, a helpful shop assistant this morning allowed me to confirm that the stalk control input on the KD-G612 accepts a standard 3.5mm stereo jack.

[pleriche]

Aha! Light begins to dawn.

The stalk controls connect various values of resistance between the pink and white wire, as follows:
Vol down: 0
Vol up: 400
Skip up: 800
Skip down: 1600 ohms
A post on another forum indicates that for a Ford Focus, the values are 50, 150, 300, 550 ohms.

Does anyone know (or can anyone please measure) what values the JVC expects? I'm within sight of my DIY stalk adapter, and will gladly share the results when I get there.

[pleriche]

One or two people seem to be reading this thread so I may as well report progress so far.

I bought the JVC KD-G612. Connecting various resistors across the stalk control input has no effect whatsoever. Putting a meter across it indicates that the live connection goes to +5v through approx 22k (if I remember correctly), strongly indicating that it's a serial data connection. May be possible to drive it from a laptop COM port via an RS232 - TTL converter (e.g. MAX232) but would take a good bit of fiddling with baud rates etc to suss it out. Gotta be worth a try before forking out £40 for a Connects2 solution.

In general my guess is that there is little standardisation in this field, which is bad news for anyone like myself trying to home-brew.

[Baldybouncer]

go to HALFRAUDS and buy an adaptor for about £20
job done

[pleriche]

Where's your natural curiosity, and your sense of fun and adventure??

Anyway, how many return trips do you estimate before they supply the right one?

[Baldybouncer]

...mmm me thinks you have been to halford before!!!!!

www.autoleads.co.uk

or ring them cos they supply halfrauds!!!

[pleriche]

OK, cracked it. For the benefit of anyone picking up this thread from Google at some date in the future, here's the result.

I bought a stalk adaptor from InCarTec for a huge sum of money. I connected the output to the mic input of my laptop via a suitable attenuator network. (DON'T try this yourself unless you know what you're doing - you risk damaging your laptop.) Then I recorded the signal with Audacity. (Any other audio editing program would do.) Attached is the result as mp3, showing the results of:
Vol+ (04)
Vol+ hold (04 repeated)
Vol- (05)
Vol- hold (05 repeated)
Skip fwd (12)
Skip fwd hold (14)
Skip back (13)
Skip back hold (15)
(decoded control codes in brackets).

The quiescent level is 5v, with 0v pulses. The coding seems to be similar to an IR controller, in fact if you used the output to modulate a 38 or 40kz IR signal, you'd probably get valid IR control codes - see http://www.epanorama.net/links/irremote.html

Essentially, 5v for 550uS represents "0" and 5v for 1550uS represent "1". There seem to be 2 start bits and one stop bit. Between them is an address (7 bits, always 47hex) and a control code (7 bits). Both are transmitted least significant bit first. The control codes are as above. The whole packet is repeated 3 times (possibly the receiver is designed to vote for the most popular if one arrives broken) and they are preceeded by an 8.5mS agc pulse.

Any reasonably bright 16-18 year old could generate these codes with a PIC microcontroller. Unfortunately I no longer need to (and anyway, I left my adolescence behind more years ago than I like to remember.)

[shirubaby]

Originally Posted by pleriche

OK, cracked it. For the benefit of anyone picking up this thread from Google at some date in the future, here's the result.

I bought a stalk adaptor from InCarTec for a huge sum of money. I connected the output to the mic input of my laptop via a suitable attenuator network. (DON'T try this yourself unless you know what you're doing - you risk damaging your laptop.) Then I recorded the signal with Audacity. (Any other audio editing program would do.) Attached is the result as mp3, showing the results of:
Vol+ (04)
Vol+ hold (04 repeated)
Vol- (05)
Vol- hold (05 repeated)
Skip fwd (12)
Skip fwd hold (14)
Skip back (13)
Skip back hold (15)
(decoded control codes in brackets).

The quiescent level is 5v, with 0v pulses. The coding seems to be similar to an IR controller, in fact if you used the output to modulate a 38 or 40kz IR signal, you'd probably get valid IR control codes - see http://www.epanorama.net/links/irremote.html

Essentially, 5v for 550uS represents "0" and 5v for 1550uS represent "1". There seem to be 2 start bits and one stop bit. Between them is an address (7 bits, always 47hex) and a control code (7 bits). Both are transmitted least significant bit first. The control codes are as above. The whole packet is repeated 3 times (possibly the receiver is designed to vote for the most popular if one arrives broken) and they are preceeded by an 8.5mS agc pulse.

Any reasonably bright 16-18 year old could generate these codes with a PIC microcontroller. Unfortunately I no longer need to (and anyway, I left my adolescence behind more years ago than I like to remember.)

Well done...this is just what I need for my remote stalk project. I'm planning to contrsuct a jvc remote wired stalk-type interface with micro switchs placed in my steering wheel. My Merc doesn't come with any controls.

HOWEVER, I am trying to understand the JVC protocol and the mp3 file. I cant see the 47hex....
From the mp3 file:
if you take the very first bit pattern after the agc pulse...it goes (reading from left to right in Audacity) 11 1100010 0100001 and then the stop bit....now if the 1st 2 bits are the start bits and the address bits are next (lsb first) we get an address of 0100011 which is 23hex.
We get a command of 1000010 which is 42 hex.

What am I missing here....

[pleriche]

Heck, this is a few months ago. Glad you found it useful.

Just taken another look at the mp3. I should have said that the waveform is inverted. Also, I probably misinterpreted the gap following the agc pulse as another "1" - there is only 1 start bit.

The address and data are each only 7 bits, "little-endian", so 47Hex comes out as 1110 001.

See the attached ascii-art waveform.

Good luck - you'll certainly have fun!

Regards - Philip

[shirubaby]

It's still not finished but a result was achieved today.

After a long time contemplating about getting round to this I finally developed (using the info above, thanks pleriche) the code to control a jvc car stereo.

The stereo I have installed in my car is a jvc kd-g421. I guess it will work with most jvc car stereos. I suggest people read the full thread before attempting to install this circuit in ones car.

The jvc stereo is coupled with an ipod integration kit (£39.99 special offer from Halfords) which means I can remotely control my ipod as well...cool. This kit (ks-pd100) charges the ipod and transfers music through the dock port on the ipod. It also allows control of ipod through the stereo buttons. So the top of the range integration kit.

The assembler code (attached) should contain everything you need to understand the pulse patterns, timings and button interfaces.

the system assumes the jvc has a remote control interface at the back which is a 3.5mm stereo jack socket.

(refer to assembler code header for diagramme1)

SIG is connected to the pic output pin. GND is earth and is the same as the stereo earth.

A 5v regulator is used betweent the pic and the power supply.

the pic input pins are tied to 5v+ so that they are held high when buttons are not in use (internal weak pull-ups
on the pic micro can also be used for this purpose where available).

(refer to assembler code header for diagramme2)

That's all! Simple huh?

[micutu]

hy, i was wondering if you can help me with this constructions, I have knowlege with electronics but not so much with PIC's. Please help me.
Can you provide a schematics for the project?

[micutu]

[shirubaby]

hi there,
Sorry for the delay. I didn;t thikn anybody would be interested in following what i did....I will get the diagrammes to you soon

[shirubaby]

have a look at the pdf