Size isn’t everything…
…unless you’re trying to cram the maximum amount of awesome in the smallest possible package. In an effort to get one of my MIDI controller boards into a 1590B / 1290 sized box, I did a respin on the PCB. Here’s a rendering:
The new board does everything the old board did, plus it has a built-in LED connected to digital pin 13 so that the standard Arduino “Blink” sketch does something 🙂 It also has a resistor that feeds 5V to one of the screw terminals. I have been experimenting with using an expression pedal on this board, and I needed to get 5V to the potentiometer in the pedal. There should be a resistor in series with the 5V so that if something drastic happens to the expression pedal or its cable, the 5V rail isn’t pulled all the way to ground.
What I found is that with a 1k resistor in series with the 5V supply and a 1K resistor in series with the wiper of the expression pedal pot (a Roland EV-5, for what it’s worth,) I get a range of ADC values from 0 to about 900. These get mapped to 0-127 in software to generate MIDI CC messages.
The new boards will be here this week, and I’m reserving them for installation in smaller projects at least until the first run of boards is gone. Functionally they are the same, so it’s not a big deal for most applications.
I’ll put up some photos of the new board when I get the first batch assembled.