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My version of Atmel AVR programmer

It can be used as regular programmer to program individual 20-pin chips, but also works as ISP programmer interface and provides RS-232 level converters. Thanks to these, you can also program the chip and run it in directly ZIF socket (in fact this is how I tested it, using demo copy of BASCOM-AVR from MCS Electronics).

Using parallel port programmer on Windows 2000 and newer can be described as problematic at best, so you might be better off just building a simple serial port plug, like this one here.

As you can see, the actual programmer part is the usual STK compatible stuff, but I also have a power supply and RS-232 level converters on board. The ISP cable has pins for RS-232 signals so that I can have debug serial interface for a projects that do not normally need RS-232 compatible port. Receiver outputs are wired through 2k resistors, so that the ISP cable can also be used to hook up the serial port parallel to the one on the project board. you cannot send anything to MCU, but will receive a copy of everything that MCU sends out.

As the power budget for a board can be a bit too much for battery-powered applications (with 74LS244 and both leds on it takes over 50mA), I added a power supply circuity which can be fed from wall-wart that outputs at least 9V DC (or 7V AC). Although it can be higher, 78L05 gets quite warm already at 12V. Using HCT series buffers and increasing R2,R3 to 470 ohm will lower the power consumption significantly, as the LS244 takes 20mA itself, and diodes with 390 ohm resistors about 10mA each.

If your project can supply the required current, you can short pins 1-2 of JP2 instead of normal 2-3, then the power for programmer will be supplied from your project through the ISP cable. As I wanted to be able to use serial level shifter on programmer board, I used 10-wire flat cable instead of usual Atmel layout. Converter can be easily constructed if needed.

I built mine on prototyping board as usual:

The most expensive part, of course is a ZIF socket, but they are just sooo neat. Other than that, you can probably build a thing out of junkbox parts. Although I used 25-pin connector for serial port so that I could use a regular modem cable, you can replace it with 9-pin part if you want to. IN any case, make sure you don't put the connector to close side-by-side, or you'll have trouble fitting both cables at a same time. I know that from experience. :)


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