PCB layout for a simple MIDI (In-Through-Out) / UART - Adapter according to MIDI 1.0 Specification
Does not directly include footprints for MIDI or TRS plugs but rather provides headers such as to more easily allow customization.
Also allows to use different voltage levels for RX, TX respectively (please use different resistors according to recommendations).
https://github.com/tschiemer/midi-uart-adapter
According to simple table-top tests using a Behringer BCF2000 all three connections (in, through, out) work as expected.
- LITEON 6N138 or ONSEMI 6N138 Octocoupler
- ONSEMI 1N914 Laser Diode
- Resistors (RA, RB, RC, RD, RE, RF) when Vrx = Vtx = 5V: 220 Ohm 5% 0.25W, Package 1206 (3216 Metric) (ex. Bourns Inc. CR1206-FX-2200ELF )
- Optional Ferrite Beads (FB1-6), 1kOhm @ 1MHz, Package 0603 (1608 Metric) (ex. TDK Corporation MMZ1608Y102BTA00), bridge if not used
- Optional
Capacitor (C1), 0.1UF, Package 0201 (0603 Metric) (ex. Murata Electronics GRM033C80J104KE15D), leave unconnected if not used (works, but too tiny package size to solder by hand; well, it's possible ;) ) - Optional Capacitor (C1), 0.1UF, Package 0603 (1608 Metric) (ex. KEMET C0603C104K4RACTU), leave unconnected if not used
The optional parts (ferrite beads and capacitor) are intended to surpress EMI etc.
| Pin | Description |
|---|---|
| Vrx | Receiver voltage (standard: +5V) |
| Vtx | Transmitter voltage (standard: +5V) |
| G | Ground |
| Rx | UART RX* |
| Tx | UART TX* |
*According to standard: 31.25 (+/- 1%) Kbaud, asynchronous, with a start bit, 8 data bits (D0 to D7), and a stop bit
Note if you are using different voltages than 5V (ie 3.3V) you need other resistor values. Also see electrical specs for suggestion.
| DIN-5pole 180deg Pin* | TRS Connector |
|---|---|
| 2 | T |
| 4 | R |
| 5 | S |
*Pins 1 and 3 are not connected.
v2.1
- Reduced size to fit into 4x5cm
- Added license on silkscreen
v2.0
- Removed unnecessary header pins
- More compact / smaller board size