The MyoTyper

Inventor	Lana Novicic
micro:bit IDE	MakeCode Editor
Best Location	Classroom

Difficulty

Hardware	Easy
Software	Medium

Special Requirement

SG90 Micro Servo	Required
Glue Gun	Recommended

Project Overview

Myotyper is a keyboard that uses EMG technology. Write only by flexing your muscles! It could be hooked up to your leg so you could write without using your arms.

Build Instructions

Materials

• 1x spiker:bit kit (spiker:bit, 3x electrodes, and 1x orange cable)
• 1x micro:bit
• 1x servo kit
• 1x glue gun (or tape)
• 1x colored paper
• 1x pen
• 1x clock hand (wood stick)

1. Choosing strew material

Choose something you will use a clock hand. It could be a straw, part of a three branch or you can 3D print it! (just make sure it's lightweight).

2. Glue servo to paper

Take a sheet of colored paper and servo motor. Glue the motor to the paper as shown in the picture.

3. Attach attachment to servo

Grab attachment from the bag came with servo kit (any one of them is okay to use). Then attach it on top of the servo. No need to screw.

4. Glue clock hand

Place the attachment onto servo. Then, glue the clock hand (wood stick) to the servo hat to align it with the servo motor attachment.

5. Write letter

Write the code and come back when you're done. Flex your muscles once to move the clock hand and simultaneously write the letters as you move it.

Code

Below is the completed code in micro:bit.

Block Code

Python

MyoTyper

letter = ""
letterIndex = 0
servoAngle = 0
numOfPeaks = 0
premg = 0
emg = 0
spikerbit.start_muscle_recording()
pins.set_audio_pin(DigitalPin.P2)
servos.P0.set_angle(0)
recordedTime = 2000
textList = ["!",
    "a",
    "b",
    "c",
    "d",
    "e",
    "f",
    "g",
    "h",
    "i",
    "j",
    "k",
    "l",
    "m",
    "n",
    "o",
    "p",
    "q",
    "r",
    "s",
    "t",
    "u",
    "v",
    "w",
    "x",
    "y",
    "z"]

def on_forever():
    global numOfPeaks, servoAngle, letterIndex, letter
    numOfPeaks = 0
    music.play(music.tone_playable(262, music.beat(BeatFraction.WHOLE)),
        music.PlaybackMode.UNTIL_DONE)
    basic.pause(recordedTime)
    numOfPeaks = spikerbit.num_peaks_in_last(recordedTime)
    # 1. move up
    # 2. select
    # 0. show
    if numOfPeaks == 1:
        servoAngle = servoAngle + 6
        servos.P0.set_angle(servoAngle)
    elif numOfPeaks == 2:
        servos.P0.set_angle(0)
        letterIndex = servoAngle / 6
        servoAngle = 0
        letter = "" + letter + textList[letterIndex]
    elif numOfPeaks == 0:
        basic.show_string(letter)
        letter = ""
basic.forever(on_forever)

Js

MyoTyper

let letter = ""
let letterIndex = 0
let servoAngle = 0
let numOfPeaks = 0
let premg = 0
let emg = 0
spikerbit.startMuscleRecording()
pins.setAudioPin(DigitalPin.P2)
servos.P0.setAngle(0)
let recordedTime = 2000
let textList = ["!", "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"]
basic.forever(function on_forever() {
    
    numOfPeaks = 0
    music.play(music.tonePlayable(262, music.beat(BeatFraction.Whole)), music.PlaybackMode.UntilDone)
    basic.pause(recordedTime)
    numOfPeaks = spikerbit.numPeaksInLast(recordedTime)
    //  1. move up
    //  2. select
    //  0. show
    if (numOfPeaks == 1) {
        servoAngle = servoAngle + 6
        servos.P0.setAngle(servoAngle)
    } else if (numOfPeaks == 2) {
        servos.P0.setAngle(0)
        letterIndex = servoAngle / 6
        servoAngle = 0
        letter = "" + letter + textList[letterIndex]
    } else if (numOfPeaks == 0) {
        basic.showString(letter)
        letter = ""
    }
    
})

Operating Instructions

• Plug the motor cable into the Spiker:bit. Stick the electrodes to your arm and connect them using the orange cable.
• Download the code onto the micro:bit and start it.
• Relax your arm and squeeze your muscles after every beep to change the letter.
• When you reach the letter you want to select squeeze twice. After each letter is selected the clock hand will automatically go back to the beginning.
• To write out the word just relax your hand and wait a few seconds and the word should appear on the micro:bit.

tip

• It takes a bit of time to get used to it but the beat helps in catching the rhythm
• You can also change/adjust the number of muscle contractions for different functions however you like