The Joat

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The Jack-of-all-trades

On occasions, I've had the need to:

  • measure the frequency of an oscillator.
  • measure the value of a capacitor.
  • measure the value of an inductor.
  • program an AVR microcontroller (for example an AtTiny85).
  • reset the "fuse bytes" of an AVR microcontroller. Well, OK, I haven't needed to do that yet, but the time will come...

Every time I've wanted to do this, I've knocked together a temporary gizmo using an arduino nano and a breadboard full of hookup wires and odd components. And then afterwards I've dismantled it.

So I decided to build a more permanent gizmo with a display and a crude user interface that can do all of the above and maybe more.

This page is intended to provide the binary files (photos, circuit diagrams etc.) of the project. When I get a round tuit.


Just about any old 2x16 LCD with a standard parallel interface would serve. I used an old LCD-compatible VFD that I had lying around. If you have an LCD with a serial interface you might have to bit-bang it because the AVR programmer uses the SPI.


Only two buttons are needed. They are multiplexed onto a single analogue input of the arduino with a resistor ladder. You could easily extend this to three or four buttons if needed. Or maybe more.

Schematic and matrix-board layout

TheJoat-schematic.jpg TheJoat-layout.jpg


Coming soon.

Source code

The source code and other technical information for the project is on GitLab and GitHub.

Round tuit

I still need to add the switchable 12v supply to power the AVR for resetting the fuses and add another mode to the menu to do the deed. I build that feature when I get a round tuit. Or when I desperately need it, whichever happens first.