MIDI Cable Tester: Simplified Design
A MIDI (cable) tester proves invaluable for numerous constructors, and the one introduced here maintains a straightforward design, as depicted in Fig. 1.
LED Indicator for MIDI Data Presence
The LED serves as an indicator, revealing the presence of MIDI data at the tester’s connection point. Given the brief nature of these data pulses, it is crucial to employ a high-efficiency LED.
Dual-Ended Construction for Cable Testing
To facilitate testing at both ends of a cable, the tester should be duplicated: one terminating in a socket and the other in a plug. A potential design is illustrated in Fig. 2.
Preferred Connectors and LED Housing
For enhanced durability, metal DIN connectors are recommended. The LED can be accommodated within a rubber support sleeve, as depicted in Fig. 3. Ensuring well-insulated connecting wires to the LED is essential.
This tests USB MIDI in host mode.
- Set the Android device’s volume to around halfway.
- Plug in the USB keyboard using the OTG adapter.
- Start either the SynthExample or the MidiScope apps.
- From the menu, select the USB keyboard. It will display the brand.
- On the keyboard, play some notes. You should hear notes being played on the phone if you run SynthExample. If you used MidiScope, you should have seen the NoteOn and NoteOff notifications on your screen.
- Unplug the keyboard. The Sender for Synth menu should display – – – – –.
- Exit the application by pressing the Back button.
Why do MIDI cables use all 5 pins?
While the connectors have five pins, only three of them are used. If you want to wire your own MIDI cable, you’ll need two male, 5-pin DIN connectors and a length of shielded, twisted-pair (STP) cable.
MIDI is electronic data transmitted over an unbalanced cable, so cable length and quality have the same implications as unbalanced audio lines: shorter and higher quality are better. 20 feet is a very safe and conservative limit for MIDI cable length. Runs of 50 feet or more are possible with high-quality cable.