trying to communicate using F Bus with a Nokia phone (an no tuto I have found is working as is ...), I got to this point :
the only time I received something back from my Nokia is when I inverted TX signal using a transistor.
Here is the wiring (red part inverts my TX signal):
As I said, this is working fine, but after seconds, transistor is getting hot, as my ATMEGA chip.
I guess I need resistor somewhere, but transistor is still confusing to me.
And when I try to add resistor to "protect" the transistor (my understanding, sorry), the only thing I do is reducing the base voltage, and Nokia does not answer my requests.
Any suggestions ?
Thank you for your help !
PS: by the way, reading the forum, I noticed that serial signal can be inverted using a library and another pin up to 115200 Baud (http://arduino.cc/forum/index.php/topic,146140.0.html
). So I'll try this in parallel, but I write down the link for future readers, and I am still interesting in a hardware solution, to understand a little more those confusing transistors ...