Add in Microbit code, tidy files, add README

Author: glenpike

README.md

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+# Intro
+
+An experiment to use Microbits to control MIDI devices.
+
+One Microbit acts as a [receiver](microbit/js/receiver.js) for others that [transmit](microbit/js/transmitter.js) values over radio.  It relays these to the serial bus (USB)
+
+These are picked up by a Ruby [programme](ruby/src/microbit-reader.rb) and converted to MIDI controller values hardcoded for a Novation Bass Station synth and sent
+
+# Setup
+
+## Microbit
+
+You need 2 of these.
+
+Paste the code for the Transmitter into the [editor](https://makecode.microbit.org/#editor)
+and download this to your Microbit.
+
+Repeat for the Receiver and leave this one connected.  Connect the Transmitter to a set of batteries.
+
+## Ruby
+
+Run `cd ruby && bundle install` to add the required Gems.
+
+In the ruby directory, run `ruby src/microbit-reader.rb` and chose a MIDI output (you need one of these).  If you move your Transmitter Microbit around, it will output the values it maps to the MIDI controllers and send to your synth.
+
+# TODO
+
+- Make the buttons and gestures do something.
+- Make synth agnostic (configurable mapping of controls, e.g. 'learn')
+- Allow ranges to be set for controllers, e.g. so we can restrict resonance, etc.
+- Make Microbit transmit without 'throttling' - do this in the ruby code (was done to reduce sensitivity)

microbit/js/receiver.js

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+// Simple Microbit programme to act as a reciever
+// - streams radio packets from other Microbits to 
+// the serial output (which is USB)
+
+radio.onReceivedValue(function (name, value) {
+  radio.writeReceivedPacketToSerial()
+})
+radio.onReceivedString(function (receivedString) {
+  radio.writeReceivedPacketToSerial()
+})
+basic.showIcon(IconNames.Pitchfork)
+radio.setGroup(1)

microbit/js/transmitter.js

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+// JavaScript for a Microbit to transmit it's orientation
+// and other input values via Radio to another Microbit
+
+function compare(current: number, previous: number) {
+    return Math.floor(current / 2.0) != Math.floor(previous / 2.0)
+}
+input.onButtonPressed(Button.A, function () {
+    radio.sendString("input: A")
+})
+input.onButtonPressed(Button.B, function () {
+    radio.sendString("input: A")
+})
+input.onButtonPressed(Button.AB, function () {
+    radio.sendString("input: AB")
+})
+input.onGesture(Gesture.Shake, function () {
+    radio.sendString("input: shake")
+})
+let lastCompass = 0
+let compass = 0
+let lastRoll = 0
+let roll = 0
+let lastPitch = 0
+let pitch = 0
+basic.showLeds(`
+    . . # . .
+    . # # # .
+    # . # . #
+    . . # . .
+    . . # . .
+    `)
+radio.setGroup(1)
+radio.setTransmitSerialNumber(true)
+basic.forever(function () {
+    pitch = input.rotation(Rotation.Pitch)
+    if (compare(pitch, lastPitch)) {
+        radio.sendValue("pitch", pitch)
+        lastPitch = pitch
+    }
+    roll = input.rotation(Rotation.Roll)
+    if (compare(roll, lastRoll)) {
+        radio.sendValue("roll", roll)
+        lastRoll = roll
+    }
+    compass = input.compassHeading()
+    if (compare(compass, lastCompass)) {
+        radio.sendValue("compass", compass)
+        lastCompass = compass
+    }
+    basic.pause(100)
+})