Thread: Renault "Tuner List" Head Unit/CD changer hacking - Controls

Originally Posted by pippolippi

So, since by connecting pin 14 to my rs232 port the led lights up, either my HU is wacky or there's a pull up resistor on the HU input.
Could you try the test I suggested on post #183?

Well, I don't have the scope anymore.
If it's not a reversed plug, I can try to borrow it again indeed, although the test by CristianC and Mox's description of the Connects2 make me think more and more that it's voltage based.

Originally Posted by Vicne

I just came across that topic with a picture of the back of an "Update List" HU and the connectors are not arranged the same way as on the "Tuner List". Are you sure of the pin numbering there ?

If the question is for me, the answer is: yes I'm sure, since I have the same model as you

Here my HU, Megane 2 - 2003 -

How I can help you? Excluding logging?

Can I be of help trying something? Me however I don't have the cd chargher. But I am very practical with the printed circuits and the pc.

Originally Posted by slimmegane

Can I be of help trying something? Me however I don't have the cd chargher. But I am very practical with the printed circuits and the pc.

Then I think we're all aiming at the first emulator, but the only one of us who has tried (Pippolippi) didn't have any result until now. If you have an oscilloscope, it would be interesting to see if you get something out of pin 13 of the blue connector when powering up the HU...

As the last version was rather outdated, here's the current version I'm using to log the protocol.

Here's what I'd like to propose as a bidirectional circuit. It's only using Op Amps as comparators, with a feedback to create an hysteresis of 12V x 1K / 5.8K = 2V. The 10K variable resistors should allow to adjust the threshold to the correct level. On the PC > HU side (right), I'd set it around 1/4 to get a 3V threshold and on the HU > PC side (left), I'd set it around 1/2 to get 6V.
As long as the PC port considers the lowest output of the LM as a RS232 "negative" voltage, it should work, I think...

Can anyone comment on this ?

***EDIT : CIRCUIT REMOVED. Probably wouldn't work due to negative voltage. A working circuit is available in post 245***

Thanks

Originally Posted by Vicne

Can anyone comment on this ?

1. from the 232 to the HU I think that you could safely leave the threshold at 0 (i.e. connect pin 9 directly to ground)
2. for the other threshold either it's not critical or if it turns out to be you need a stabilized reference, I don't know where you're going to take the 12v but I doubt that if they come from the car battery they're stable
3. the bridges 1-6-4 and 7-8 in the rs232 connecor are unnecessary, after all you're writing your own software so you can ignore those signals. Connecting 2, 3 and 5 is enough (probably using one of 6-DSR or 8-CTS for the remote signal)

Originally Posted by Vicne

Can anyone comment on this ?
Thanks

It's ok for the side HUTX -> PCRX only if HUTX isn't an open collector, becouse with an open line the output level is unknown (can be 0 or +12v).
For the side PCTX-> HURX i'am not sure it will work becouse when the tx line goes negative with the resistor divider 1K-5.8K the input V- of opamp will be exposed to a negative voltage causing a malfunctioning of the output. (from datasheet Note 6: This input current will only exist when the voltage at any of the input leads is driven negative. It is due to the collector-base junction of the input PNP
transistors becoming forward biased and thereby acting as input diode clamps. In addition to this diode action, there is also lateral NPN parasitic transistor action on the IC chip. This transistor action can cause the output voltages of the op amps to go to the V+voltage level (or to ground for a large overdrive) for the time duration
that an input is driven negative. This is not destructive and normal output states will re-establish when the input voltage, which was negative, again returns to a value greater than −0.3V.)