M5Stack U187 MIDI in the house - Sand, software and soundSand, software and sound

Here are a few pictures of the M5Stack U187 MIDI unit, U125 buck converter and cables.

M5Stack MIDI Unit and 5V buck converter

These M5Stack parts are tiny. I included an SD-sized adapter in one of the pictures in order to convey a sense of scale.

The M5Stack modules interconnect by way of 4-pin JST connectors (GROVE). I plan to use the U187 MIDI Unit as a standalone MIDI module powered by the 5V buck converter and an AC adapter. The buck converter requires a center-positive adapter cable, by the way — a simple fact not mentioned in the converter’s description.

The U187 MIDI Unit has MIDI IN on 5-pin DIN and 3.5mm jack. It has MIDI OUT on 5-pin DIN and 3.5mm jack. The slide switch controls internal signal flow. Optionally, one can pass the MIDI IN through to the MIDI OUT as shown in the routing diagram.

The next step on the way to musical joy is figure out the wiring. The short ribbon cables are “unbuckled”, a term which I have not encountered before! “Unbuckled” seems to mean straight-through. In other words, when you look at the JSTs in the same orientation, pin 1 is white on both, pin 2 is yellow on both, etc. Conceivably, one could have a “twist” that reverses the signal order.

Why worry, Alfred? The buck converter has a JST connector, too. The +5V and Ground pins are live while the two “data” signals are unconnected (NC). I plan to short the U187 TXD and RXD signals, and when push comes to shove, I do note want to accidentally short +5 and Ground!

M5Stack color-code their JST ports, thank goodness. The U187 port is blue and matches the blue PORT.C UART JST on their controllers and bases. This should help me do the matchy-matchy when wiring. I plan to double-check power using a multi-meter. It’s not the expense ($15) of blowing up the U187 as much as the time wasted ordering a replacement and waiting on delivery.

One Dream SAM tidbit. Dream have formally declared the SAM 2000 series synth chips as end of life (EOL). The window for final orders has already closed. Dream have asked customers to move on to the SAM 5000 series.

M5Stack U187 MIDI Unit inside

The image above shows the inner guts of the M5Stack U187. The U187 case is held together by a tiny hex screw and lucky me, my smallest hex wrench got the job done. You see the Dream SAM2695 in the shot. Long live the 2000 series!