As seen on LittleBits: https://classroom.littlebits.com/inventions/littlebits-arduino-midi-master-clock-with-tap-tempo
You can also do this with a regular Arduino, but you'll have some extra work soldering the button(s)/dimmer
See the excellent tutorial at this link: http://www.instructables.com/id/Send-and-Receive-MIDI-with-Arduino/step3/Send-MIDI-Messages-with-Arduino-Hardware/ .
Or check the electrical spec here: https://www.midi.org/articles/midi-electrical-specifications
- Connect MIDI ground to Arduino ground
- Connect MIDI 5V to Arduino 5V with a 220 Ohm resistor in between
- Connect MIDI signal line to Arduino serial input pin (D1)
Connect a button to D2
- Upon startup, Arduino will start sending 100 BPM MIDI clock signal (or last saved BPM value if available).
- Tap the tempo (minimum 3 times)
- After the last tap, clock tempo will be updated and MIDI clock signal will send new BPM
- MIDI clock output on pin D1 TX
- Tap tempo input
- Dimmer input when a dimmer is connected to A0 to set the tempo by twisting the knob!
- Tempo blinking LED on pin 5
- Sync signal on pin 9 (for example to sync with Korg Monotribe...)
- MIDI real-time start/stop is sent when button press is detected on A1 port
- BPM storage in EEPROM and restores it on power up
- MIDI forwarding if a MIDI input is present on pin D0 RX
- Output of the BPM to a TM1637 LED display
- master: Code for the Arduino Leonardo (or LittleBits Arduino)
- arduino-uno: Code for Arduino Uno and compatible devices (D0/D1 RX/TX pins are used for MIDI in/out, so no debug console!)
- olimex-midi-shield: Based on the arduino-uno branch, but with some tweaks to make the code work better with the Olimex MIDI shield (https://www.olimex.com/Products/Duino/Shields/SHIELD-MIDI/open-source-hardware) (Work in progress!)