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

Originally Posted by guest

I think that the signal is inverted but ready to connect to rs232 of PC. The idle level output from uart is logical 1 ttl (4-5volt) but when you interface the rs232 the levels are inverted and idle is 0Volt (belove 3v).

Mmmh... Except that logical 1 in RS232 must be a *negative* voltage (between -5 and -15V), so I think the MAX chip is really needed

Originally Posted by Putput

I had a quick look into your results and there are a lot of '1's in the bitstream. Try inverting them, perhaps this could make more sense.
Then you have 2 groups of zeros which could indicate disk 1, track 1 ?? And the last byte inverted reads as a GS or Group Separator

Yes indeed... I think it will be much easier when we've got more samples to work on, to compare successive values. That's what I'm working on right now...

Keep up the good work, I'm very interested. Perhaps I can assist you writing software to access the serial port, I'm currently working on software to link my GSM via serial port over Bluetooth.

Perhaps you can help me indeed. See post below.

Thanks for your proposal.

Well, levels are now OK.
Here are the adaptations I made to the spy circuit :
- lower the input voltage with resistor dividers. I chose 68K and 22K, giving me a factor of 22/(68+22) ~= 0.25. So input level of 3V gives 0.75V and 12V gives 3V, which is perfectly in the working range of the MAX circuit - see data sheet on http://pdfserv.maxim-ic.com/en/ds/MAX3222-MAX3241.pdf
- tie pin 1 of each serial port with already connected pins 4 and 6, following the recommandation of the first schema on http://www.airborn.com.au/rs232.html
- fixed the errors in the wiring of the second serial port

These changes are included in the schema below.

*** EDIT : Schema removed again. Signal needs to be inverted !
Working circuit available in post 197 ***

Now I have a "perfect" signal. The scope captures below are from pins 11 (T1IN) and 14 (T1OUT) of the MAX3232, respectively. So obviously, I'm in the correct range...

However, on the PC, I cannot get anything in Hyperterminal or MTTTY (sample MSDN application - see http://msdn.microsoft.com/library/de...sdn_serial.asp )

I see two possible reasons :
- Wrong wiring of serial port
- Loopback handshake is not supported by these apps.

Can someone with experience on serial communications (Putput ?) comment on this ?

Thanks - the mission continues...

Originally Posted by TheLlama

what are you all using for Oscilloscopes?
...
I guess I could use my PC's sound card...

It might be worth checking this

Vicne, may be this could help to : http://rt3wiki.free.fr/pmwiki.php?n=Us.Document

It deals with Peugeot's RD3 Headunits on a VAN bus, but the idea is the same : fool the HU into thinking there's a CDC.

Originally Posted by Putput

Hard to tell, has probably something to do with port settings and/or handshaking. When nothing gets trough the port seems to blocked or waiting for something, try this http://www.serial-port-monitor.com/d...t-monitor.html program instead of Hyperterminal to monitor, its free.

Thanks. Mox already pointed me to it, but as I read the description, I thought it was only an "interceptor" between a working Windows host application and a remote device. In my case, as I have no windows app (yet) to communicate with the head unit, I thought it was useless.

Although, I just downloaded and started it and this seems that as soon as hyperterminal opens the port (no matter if settings are correct or not), the monitoring begins even though hyperterminal doesn't display a single character. I could only test it with an old serial mouse for now, but I'll give it a try at home tonight.

The only thing that I'm still unsure of is the wiring of the DB9 plug...

Thanks again.
(and sorry Mox not to have followed your advice at first)