Arduino Standalone RS232 Communication

Hi,
I have soldered a standalone arduino on a custom pcb and Ihave some problems with programming the Arduino by the IDE over a RS232 connection. I soldered the microcontroller to the dsub connector as shown as in this picture :

[note : I had nothig connected to the reset pin of the microcontroller]
When I tried to load a sketch on the microcontroller, it did not work. I found out later that I have to reset the microcontroller right before the IDE starts to send data to the microcontroller. I tried to do this with a BC548 transistor hooked up to the DTR signal from the RS232 which switches the reset pin to ground when DTR is high, but it didn’t work too :roll_eyes:
Schematic of my failed DTR reset circuit :

I hope someone can help me with this reset-problem :slight_smile:

DTR is created as a level. You need to turn it into a pulse.
Run it thru a 0.1uF (100nF) cap to the reset pin, reset pin needs a 10K pullup resistor.

Thanks! Going to try it tomorrow.

Put the capacitor in series with the 4k7 R1 in the present circuit. Done!

The caps were delivered today. Connected them in series to R1 an it worked perfectly , Thanks! 8)