Hey all. I’m looking through the all-in-one midi out circuit here: https://discourse.zynthian.org/uploads/default/original/2X/9/983f30a1a1e8cf0824b0e4fc3f71ab27aa0e006d.png
and noticing that the LED connects to pins 3 (cathode) and 4 (anode) of the MIDI-3 header and looks like it would only get forward biased (turn on) if the output of OC3 goes below gnd, which doesn’t seem likely. Even if the build instructions are simply incorrect and the anode and cathode are switched, shouldn’t there be a resistor to control the current through the LED? Finally IIUC the LED should turn on when the midi-out signal is high, which will make pin3 of MIDI-3 to go to gnd. So for the led to activate pin 4 must be tied to 3 or 5v. The same is true of the midi-thru circuit. This only affects the LED operation, so luckily its not a big problem for those who already have boards.
So I propose that pin 4 of MIDI-2 and MIDI-3 should connect to a 100 ohm resistor which is tied to the 5v rail.
It’s of course possible I’m getting it wrong too though.