Create a MIDI connector
See excellent information here:http://www.instructables.com/id/Send-and-Receive-MIDI-with-Arduino/step3/Send-MIDI-Messages-with-Ard...
I bought a male-to-female MIDI extension cable, and cut it in half.
Then I stripped the cable and added the 220 ohm resistor. The resistor is in the green electrical tap you see on the picture.
I used a proto module to connect the MIDI adapter to the littlebits Arduino.
Make the littleBits setup
Power module -> button -> D0 port of the little
D1 port of littleBits Arduino -> proto module -> MIDI adapter cable -> Your MIDI device
Add the TimerOne library in the Arduino application
In the Arduino application:
Menu -> Sketch -> Include library -> Manage libraries ...
Search for 'TimerOne' .
Install the library!
Upload the code to the littleBits Arduino
Use the Arduino application to upload the code to your littleBits Arduino.
... and see the BPM change in your connected MIDI equipment!
(Make sure to set your gear to 'external clock source')