Week 3: Make the FabISP in-circuit programmer

The assignment this week was to make and populate the circuit board for the FabISP programmer.

1. Mill the circuit board on the Modela milling machine. The class website has a good Tutorial covering the details. The file that I used is Hello.ISP.44.cad

Some things to watch out for:

• Don't overtighten the endmill set screws, but be sure that they are tight enough that the mill does not slip.
• Make sure that the circuit board is flat.

2. Clean with isopropyl alcohol. Collect parts for soldering. One good idea is to make a part list on paper and attach parts by double-stick tape near the appropriate text.

3. Soldering. A few tips:

• Especially on many-legged parts it is best to attach one leg to a pre-tinned pad, solder the remainder, and finally return to solder the first.
• The USB connector has very fine, closely spaced traces. It is possible to apply too much solder, bridging the traces, and remove it with solder braid, leaving solder only where it needs to be, and looking very shiny.

Here's the board.

Notes at the end of the semester:

This week's documentation was sparse, due to my perception that most of the steps were covered well in tutorials, and due to the fact that I was still occupied with Week 2. It turns out that the ability to mill and populate a board with fast turnaround is crucial to the success of all the embedded programming weeks. It is important to practice this, starting with the mechanics, as we did in this week, and later adding the ability to design and program.