MP3Car.com - View Single Post - Renault "Tuner List" Head Unit/CD changer hacking

Ale · 02-08-2006, 06:46 PM

He Vicne i'am the guest of yesterday.
The problem is that the headunit output an inverted UART signal and instead max232 input need a normally 1 TTL level on pin 11 (the start bit sholud be level 0 TTL) so pin 14 will be normally at -5V and output a start bit at +5V. if you put an inverter (or a NPN transistor with a pullup resistor of 10K to V+ on the collector) between the divider and pin 11 all should work fine. Check for confirmation the idle level output of your PC RS232 pin tx, should be -5 to -12V. Keep in mind also that if the signal is inverted the parity now is EVEN.
good luck!
Ale

02-08-2006, 06:46 PM	#25
Ale Newbie Join Date: Feb 2006 Location: Italy Posts: 42	He Vicne i'am the guest of yesterday. The problem is that the headunit output an inverted UART signal and instead max232 input need a normally 1 TTL level on pin 11 (the start bit sholud be level 0 TTL) so pin 14 will be normally at -5V and output a start bit at +5V. if you put an inverter (or a NPN transistor with a pullup resistor of 10K to V+ on the collector) between the divider and pin 11 all should work fine. Check for confirmation the idle level output of your PC RS232 pin tx, should be -5 to -12V. Keep in mind also that if the signal is inverted the parity now is EVEN. good luck! Ale