It has been quite a while since my last update. My wife messed up her knee two weeks ago, so between being Mr. Mom and working for The Man, there was no time to tinker. My hat is off to all of you single parents and caretakers who find time to tinker!
Anyway, finally got around to finishing my ATtiny Programming Jig. In Part 1, I covered the functionality of the Jig using a breadboarded solution. Now in Part 2, I take it one step further and develop the schematic into an Arduino shield. Creating a shield greatly simplifies the Jig’s use, as no jumper wires are needed. The shield snaps onto the Arduino in the correct position and is immediately ready for use, as in the image below.
Getting there was the hard part. It took me about three tries to get the toner transfer correct. Rather than using the popular glossy photo paper method, I chose to scavenge a few of the wife’s gossip magazines. The results kept coming out rather weak until I found all of the correct print settings for my Mac. The key was to set High Quality and Transparency. For etching, the choice was simple. We have a large swimming pool behind the house, so I reached into my pool supplies shelf and used some of the Muriatic Acid I have. Strong stuff. Within 10 minutes in the freezing garage (it was 25F/-4C today) the board was ready. A bit of milling and drilling got me ready to go.
I placed the parts, soldered and plugged it in for testing…
Green light on, good! Picked a random bit of code I had written for the ATtiny and avrdude came back complaining the processor does not look right. Ouch! All that effort and it does not work? Started tracing all of the paths on the board until I found the problem. For some reason I had forgotten to map the Arduino pin 12 to the MISO bus. Not sure how that happened, as the schematic is correct. For some reason I must have missed that connection in Eagle when mapping the traces. Once the problem was found, a quick soldered wire solved the problem.
Once the new wire was soldered into place, I reconnected the shield to the Arduino and tried to upload again. SUCCESS!!
I will have to go back into Eagle and update the board with the new trace, but that is for another day. I will post an update when I have the board fixed and will publish the Eagle layout. Then onto my next project – animating an ancient backup tape!!
Edit: The revised board layout is available here: ATTiny Programmer.brd