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by anonymousiam 1525 days ago
I've used my parallel port as a JTAG (IEEE-1149.1) interface to reflash/debug embedded targets. It's slow, but it works.

http://zoobab.com/simple-jtag

2 comments

When I was young, I used it for a morse code decoder, and then later to decode magstripe data from a reader circuit I made with spare parts. QBasic made it trivial to interface with! I remember being able to achieve toggles at near a MHz with QBasic, since it was just a memory write.

Having that many IO, ready to go, was really great. I bought a separate ISA expansion card so I wouldn't burn out my motherboard's port. Now, you can get a little USB powered micro python board for the same price!

PIC and AVR microcontrollers can be programmed using a parallel port; passive adapters with nothing more than resistors used to be common.