Travis Rich -- HTMAA

week 1 Proposal
week 2 Press Fit
week 3 FabISP
week 4 3D
week 5 PCB
week 6 Casting
week 7 ATtiny
week 8 Big
week 9 Input
week 10 Epoxy
week 11 Output
week 12 Interface
week 13 Network
week 14 Machine
week 15 Final

Week 3 -- FabISP


FabISP Intro

This week we're learning how to mill circuit boards, solder components, and program the previously mentioned boards. We'll be making a FabISP (in-system programmer) that will be used for the remainder of the course to program any other boards we go on to design.


I milled my first board directly after the training sessoin, so everything was fresh in my head. I used the older machine, so I had to be a bit careful about the sacrificial board being warped. I tested my z-height in several locations to make sure I would always be hitting the board. In the Fab Modules, I set my 2D z-depth to 0.12 and got nice results from the cut. Instead of using the Modella to cut out the board, I decided to try the pressure chopper. I messed up the board on my first cut by going too slowly. The proper way is to line up the board, hold the board firm, and do a nice quick, chop. By going slowly and not holding the board completely tight, I gave the FR1 a chance to splinter and crack - which it did. On my second iteration, I used the Modella to cut out the board.


Soldering all the components onto the board went fairly smoothly. For the components with very small leads (the microprocessor and the usb jack) I made a long solder bridge across all of the leads and then used copper solder wick to pull off the excess. This produced nice results with no bridges and little excess.

The key to soldering these boards, for me, was a good pair of tweezers. Being able to finely manipulate all of the components made the process quite smooth.


Programming I ran into some issues the first n times around. My first mistake was leaving the make file unchanged when trying to program my board with another FabISP. Some tutorial somewhere said to do so when using FabISPs, but it must have been referencing a different Makefile. I eventually got help from Eyal Toledano who lent me his commercial product ISP. This worked right away (as expected in hindsight, since the Makefile was setup for that). I used the directions he laid out in his Week 2 writeup. The key of this writeup was running the command 'avrdude -c usbtiny -p t44 -P usb -U flash:w:main.hex:i' once everything was connected. Once everything was programmed, I verified the success of everything by first checking that my computer registered a connected USB device with the name 'FabISP' and second by programming another students board with my board.