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In circuit AVR programmer (ISP).

Perhaps this circuit is the simplest AVR programmer you can build. Its great advantage is the ability to program almost any AVR microcontroller, without the need to remove it from the circuit in which is connected (in circuit programming).


Actually the circuit is a simplified version of the older SIProg programmer. For more details read the article A simple SI-Prog.

Almost any AVR based circuit presented in this website is compatible with this programmer.


  • Two Zener diodes at 5.1V (low Watt).
  • One 10K resistor (1/4 Watt).
  • Two 4.7K resistors (1/4 Watt).
  • One 15K resistor (1/4 Watt).
  • One BC547 npn bipolar transistor.
  • A female 9 pin DSUB connector (for PCB).
  • A female pin header (5 pins. If you have one with more pins, just cut it).
  • A small piece of a Veroboard.
  • Wire for connections.
  • Solder and soldering iron.

You don't need any external power supply.

Schematic Diagram

Here is the schematic diagram of the In circuit AVR programmer

Attention: In order this programmer to work, the circuit in which the microcontroller is connected, must have a 10K (or 4.7K) pull-up resistor on AVR's reset pin.
Generally we call pull-up resistor any resistor connected between the power supply and one of the I/O pins of the microcontroller. On the other hand pull-down resistor is a resistor connected between the I/O pin and the ground (GND).


In order to succesfully program the microcotrollers, you will also need the appropriate software. You can find a lot of free software compatible with this circuit. However in this article, I will show you the settings only for icprog (www.ic-prog.com) and PonyProg (www.lancos.com/prog.html).

For ic-prog you can see the necessary settings in the following picture

If your computer isn't fast enough, increase the I/O Delay. With a Pentium II 333MHz, I didn't have any problems with the delay.
Attention: In order to use the Direct I/O interface setting in Windows XP, you need to download the appropriate driver from the icprog's website (www.ic-prog.com).

For PonyProg the settings are just like the next picture


In the following pictures you see the programmer build on a small piece of a Veroboard (StripBoard).


Created: 12/11/2008
Updated: -

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