Week 08

input devices

Tools & Materials

  • Eagle
  • Roland RSM-20
  • PCB


This week I worked on a step response pressure sensor, which I hoped would feed into my final project.

Designing the board

I used the ‘hello.load.45’ board as a reference for this week’s design, and laid out the components in Eagle. I used an attiny45 as the processor and a 2x2 header to eventually speak to the pressure sensor pad.


I ran into some issues later programming this board, so would come back to it often to double check that everything was laid out properly.


Milling and Building

I’m getting more familiar with milling on the Roland RSM-20. I used Mods to speak to the mill, a 164” endmill to cut the traces, and a 132” endmill to cut the board outlines. After the first board was done, I moved over the endmil origin position, and used the same board cut file to cut a pad to press down on.


I’m getting more familiar with soldering, but the attiny45 was harder to solder than I remember. I blame this on the fact that I ran so many traces under the board this time–it was difficult to see the pads in most cases.

When I remake this board, I’ll likely use a reflow method and the heatgun rather than the soldering iron.



I used my USBTiny to try to program the attiny45, but saw an issue off the bat–the green LED should have been off on the USBTiny when I plugged in my new board. Since it was on, I was likely sending voltage that I shouldn’t have.


Paloma helped me troubleshoot with the multimeter, and confirm my layout in Eagle, and we came to the conclusion that there was likely something going on under the processor.


I removed the processor from the board by holding the processor with tweezers and aiming a heat gun at it (alternating frequently between each side). The processor dropped to the table, and I could see that two of the pads were connected that shouldn’t have been.


I used a soldering wick to remove the solder and tried to even everything out with the soldering iron before applying a new processor.


Programming the board

First, I tried programming the board using the Arduino IDE and the hello.load.45 files. There weren’t any errors, so everything seems to have been sent smoothly, but I wasn’t able to get any reading out from the serial port.

I tried programming the board using the Ubuntu virtual machine and terminal, but am currently trying to make sense of this error: