Tao of Mac

Jun 4th 2022 · 4 min read

Weekend Updates

Since I got something like 15 little packets from AliExpress, so I finally have all the parts for my electronics builds and can get to finishing them.

MIDI Expression Controller

The guts of the thing are little more than a WaveShare RP2040, a tiny OLED display and a pushbutton, but they need a little bit of software to act as a MIDI USB device, so I’m playing around with CircuitPython.

And I must say it is pretty amazing for this kind of project–you get I2C, MIDI over USB and hot code reloading out of the box, and what took the most time so far was soldering some pins on one of the boards and wiring up the breadboard:

This is after writing less than 50 lines of Python, which is pretty insane.

The only drawback is that CircuitPython seems a little slow to send MIDI updates, so I might switch to Arduino/C++ later depending on how well it performs in use.

And picking up on last week’s idea about , I started designing the case for it by wrapping the linear pots in a nice curvy hull:

The slight inclines and rounded corners would otherwise be quite hard to do.

Not Quite Smooth Sailing

But I still need to make work properly, so I took the time to go through a number of test prints, including the infamous 3D Benchy:

It doesn't look half bad, but still needs work.

After the first round of tuning, and since we now have a new set of Teenage Engineering Pocket Operators in the house I printed out this Pocket Operator case as a test:

This seems OK, but there are a few gaps near the LED slots I'm not happy with.

This was a good test for troubleshooting first layer printing and Z-axis flattening, but printing the buttons has so far proven impossible since my printer has a lot of trouble with repeated filament retractions and precision moves, and reducing speed didn’t help.

So I started going doing simpler test prints to troubleshoot one thing at a time:

Trying to get rid of ghosting and minor layer irregularities

Tuning Mishaps

Part of the tuning involved getting some pliers out and tightening the X and Y axis belts, which have become loose over time.

However, one of the bolts froze and required a lot of torque that partially damaged the Y axis mount, so I ended up having to print a new support piece:

More complex, irregularly shaped prints turn out worse.

This is when I realized my extruder is having a little trouble (that’s the reason for the little holes in some layers). So I’m again looking at getting a new printer, preferably something with an all-metal construction (fortunately, the market seems full of Ender 3 clones).

And while I sort out the printing side of things, there’s plenty of time for doing some more electronics…