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

Here's a simplified circuit that I tested today



I actually used two 3k3 resistors (edit: in parallel) instead of 1k5 in series with rts, but 1k5 should be fine.
I removed the optocoupler that indicates that the HU is on (the software doesn't need it anymore) and the transistor facing HU RX (which is now directly connected to the optocoupler output, the inversion is made by reversing the led polarity).

Originally Posted by pippolippi

I don't know either, probably the startup sequence is different since I don't try to completely emulate the cdc.

I send:

Code:

  def startPacket(self):
     """Tries to send the initial packet"""
     time.sleep(0.5)
     self.flushInput()
     self._sendsequence=0
     self._recsequence=0
     if self.sendPacket('\x11\x60\x06'):
          self.sendPacket('\x25\x03')
          self.sendPacket('\x26\x05\x01\xFC\xFC')
          self.sendPacket('\x25\x03')
          if self.sendPacket('\x20\x01\x03\x09\x05\x01'):
              return True
     return False

I now found that if I omit the 260501FCFC (random off) packet the HU won't send "random on" on startup. So it seems that if the HU sees that the CDC is in an "incorrect" state it will try to correct it. It's good to know since this way it's not necessary for the PC program to store random state: always say that's off and the HU will correct that.
I also found that the minimal startup sequence is
116006
200103090501

The last packet (200103090501) indicates to the HU which cd is playing, and I'm not sure it is needed.
Anyway I factored it out in a separate function

Code:

  def playingCD(self,number):
    """Sends the cd number currently playing"""
    return self.sendPacket('\x20\x01\x03\x09\x05%s' % chr(number))

and I found that the HU is capable of displaying CD numbers up to 9 (i.e. it's not limited to 6), a bigger value will show a blank. Didn't try with 0, I'll try later on.

Originally Posted by pippolippi

indicates that the HU is on (the software doesn't need it anymore) and the transistor facing HU RX (which is now directly connected to the optocoupler output, the inversion is made by reversing the led polarity).

I'm thinking that the protection diode after RTS is maybe useless: the optocoupler output transistor is still seeing all the reverse voltage in case DTR is high and RTS is low.
Instead of connecting this way

Code:

        _____
5  ----[_____]---|<--- RTS


4  ------------------- DTR

maybe I should connect it to shunt the reverse voltage:

Code:

        _____
5  -+--[_____]-------- RTS
    |
    -
    ^
    |
4  -+----------------- DTR

what do you think?

Originally Posted by pippolippi

[code]
_____
5 -+--[_____]-------- RTS
|
-
^
|
4 -+----------------- DTR

That's are the better solution i think, why some reverse voltage?

Anyway I'm emulate my CDC without any resistor or transitor, but only the ACTIVATION features work the other features doesn't work.

bye
peppe

Originally Posted by peppuz79

why some reverse voltage?

Because you cannot know the state of the RTS and DTR lines when connecting the interface (only after starting the program you can be sure).
In the worst case DTR could be +9V and RTS -9V, so the transistor will see an emitter-collector voltage of 18V, while its datasheet says the maximum is 7V.

This is the final circuit:

Originally Posted by Vicne

So, Pippolippi, I'm intending to build the circuit you just posted, and I have a few questions:
- Is it "validated" :-) with your HU ?

Yes

- I intend to use the RTS also to power my relays (via a transistor of course). So I guess I should come back to two separate 3.3K resistors, right ?

Probably, one resistor to feed the optocoupler and another to feed the base of the transistor, yes. Or you can leave the 1k5 resistor and try, say, with a 10k to feed the transistor. Don't forget to put a diode (1n4002) across the relay to protect the transistor. But I'd try it on the breadboard before soldering.

- If I'm using 2N2222 transistors and CNY74-2 opto-couplers, do you think I need to adapt some resistor values ?

I don't think so, but then I didn't really calculate the values