Add Auto Reset - maierma/avr-netino GitHub Wiki

##Introduction The auto reset feature from arduino boards enables the PC to reset the board by toggling the DTR line of the serial connection.

You can add this to your AVR-Net-IO board by soldering a capacitor between DTR and Reset. Or alternatively (see comments below) between RTS (through MAX232) and Reset. Optional, but suggested, add a diode from Reset to Vcc.

##Details The suggested circuit looks like:

DTR:  J5-4
   or    o-----||-----+-----|>|-----o Vcc 
RTS: IC4-9   100nF    |    1N4148   IC5-10
                      |
                Reset o IC5-9

When avrdude starts a download it will take down the DTR line and thus giving a short pulse over the capacitor to reset the ATmega.

I've observed, that sometimes after finishing the download, when DTR goes high again, the ATmega hangs. I've figured out, that this is caused by the high pulse on Reset. I think this confuses the ATmega, because a higher voltage on Reset will enter High-Voltage-Programming-mode. With the additional diode I haven't this problem any more.

##Instruction I've soldered the capacitor (100nF)on the bottom of the PCB. From the serial connector (J5) pin 4 to the ATmega (IC5) pin 9.

The diode, a 1N4148 I've put on top side, on-top of R 12, which is the pull-up resistor between Reset and Vcc.