Project 3: Make a printed circuit board using the Modela NC mill and the vinyl cutter, make cables for it and program it so that it says "hello world" on the computer.
-- rigid circuit board --
I machined a circuit board using the Modela mini mill. I then cut the board out using the scroll saw.
I stuffed the board, i.e. soldered on all the parts, which was sort of perversely fun.
-- flexible circuit board --
I used the vinyl cutter to make a flexible circuit board.
First I cut copper at a setting of
I then removed the board with masking tape and transferred it to the clear backing by pressing hard to activate the pressure-sensitive adhesive. I then weeded the board by removing the copper that is not a part of the board.
Again, I soldered on all the parts. I unfortunately made the mistake of using double-sided tape to secure my flexible circuit during the soldering process.
Of course, when I went to unstick the circuit from the table, the strain broke half my solder joints and I had to re-do them. This was tough and my board ended up looking really ugly.
-- cable making --
We had to make two different cables. My Cablebuddy was Michael Lapinski.
One was a parallel cable that will allow us to download the "hello world" program onto our circuit board.
After clamping down one side, we stripped the necessary wires, put some solder on them, and attached them to the necessary pins. Each wire was covered in shrink wrap.
The other is a serial cable that allows the circuit board to talk to the computer and also allows it to be powered by the computer.
We clamped one side and then stripped the necessary wires on the other side. We found that it was important to cut the wires to as close to the same length as possible in order to minimize stress when plugging them into the molex.
-- making it work --
In one terminal rx.py is run to power the circuit board. In another terminal window the command line
avrdude -p t13 -c bsd -U flash:w:hello.hex
is run to program the board.
For the longest time I could not get my circuit board to display "hello world" on the screen. It would just spit out gibberish.
I checked all the connections, the power, looked at the solder joints under the microscope. Everything seemed to be a.o.k.
My friend helped me use the oscilloscope to see the signal coming out of the chip. I compared this signal with Neil's board (which of course worked perfectly) and the signals looked exactly the same! We thus realized that the problem must be something downstream of this.
"Plug the serial cable in farther" my friend suggested.
I shoved the cable in a little bit more and
BLAMMO.
It worked.
Here is a screenshot:
