Sunday, May 11, 2014

Building a Headerless Programmer

In my previous post, I talked about a circuit board that uses force-sensitive resistors as end stop detectors. This board has an Atmel ATTiny861 microcontroller that needs to be programmed. For the first few boards that I made, I soldered headers in place. This works just fine, but I wanted to see if I could use pogo pins that I purchased form Sparkfun to create a programmer that doesn’t require the header pins.

For this project I needed six pogo pins, one 2x3 pin header, and some ribbon cable that I pulled apart so I could have six wires, each with a different color. I 3D printed parts to build the jig, which are shown below using “clear” PLA filament.

First I soldered the wires to the 2x3 pin header, and then pushed it into place. Next I soldered the wires to the bottom of the pogo pins, after I’d inserted the pogo pins into the 1.6mm holes in the jig:

OLYMPUS DIGITAL CAMERA

I was concerned about the possibility of shorts, so I added short pieces of heat-shrink tubing to the very end. Since building this, I read somewhere that these pogo pins will fit directly into a female header—that would have been a lot easier.

Here is what the jig looks like when finished. You can see the six pogo pins sticking out the top, and the programmer cable hooked up to the 3x2 pin header:

OLYMPUS DIGITAL CAMERA

Finally, this is what it looks like in use. I hold the board in place (there are two alignment pins) while I click the button the upload the program to the board.

OLYMPUS DIGITAL CAMERA

While this works very well, it was more work to build than I would have liked. As I mentioned, using a 3x2 pin female header would have been al lot easier, and I’ll use that approach if I build another programmer.

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