In general, in the schematics I have given, the values for the resistors and capacitors are not very critical. I made this programmer mostly from parts I had around, I tried not to put much too power through the resistors, or exceed the working voltage of the capacitors. The transistors used are not critical, as long as they are bipolar, can supply adequate current, and they are the right polarity (NPN or PNP). This article is not meant to be an introduction to electronics, so you may have to do some research to make sure you are choosing the right parts.
I built this programmer using wire wrap techniques on perf board. I used stand offs to mount it on a piece of copper clad that I had around. I have no plans to make a printed circuit board, since I have no plans to mass produce it. For simple projects like this, wire-wrap works great for me.
10/14/98 UPDATE: Fixed a minor error in the interrupt code that runs the serial port. The circuit works without the fix, but I don't like to see an error like that survive.
5/31/98 UPDATE: The first version of the (Linux-tested) perl driving code is complete, and wonder upon wonders, *it works*! I hope to find some other people who are willing to help me test the software. If you are, please contact me at the address at the bottom of this page, and I will give you all the help I can.
4/17/98 UPDATE: I'm still working on the Perl code to drive the programmer from Linux. Strangely enough, it was much easier to get the programmer to work under Windows NT. Right now, the framework for the code is in place, I'm just having problems with reliable communication with the serial port. I have received a lot of very helpful feedback, and I appreciate it. This feedback has inspired the idea of the V2.0 programmer. This V2.0 programmer is a while off yet, but it will incorporate most of the hardware changes I envision. For the programmers with revision level < 2.0, I will only make hardware changes that do not require a change in the firmware, and these changes will be minor changes, mostly for reliability.
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