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Topic: Arduino Standalone RS232 Communication (Read 944 times) previous topic - next topic


Oct 10, 2013, 08:49 pm Last Edit: Oct 10, 2013, 08:53 pm by Me262 Reason: 1
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 :smiley-roll-blue:
Schematic of my failed DTR reset circuit :

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


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.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.



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)

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