The now obsolete (and sold second hand for $30-50) Native Instruments KORE and KORE 2 controllers are great hardware for a MIDI control surface. Although NI released a firmware enabling the KORE and KORE 2 to be used as generic MIDI controllers it still require a driver to run on the connected computer. And the latest driver for MAC does not work on latest MacOS releases.
As I was looking for hardware to make a MIDI controller to control Amplitube for my bass guitar playing, I bought a used KORE 2 and started playing with Arduino BLE MIDI on Nordic Semiconductors nRF52840.
The implementation includes a Mega 2560 PRO board and an Adafruit ItsyBitsy nRF52840 Express. Some nice 3D printed caps allow the Bluetooth signals to be broadcast out of the metal enclosure.
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.