c_meyer/pxt-calliope

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Peli de Halleux 89406330cf rename micro:bit to @boardname@

2016-11-01 17:44:37 -07:00

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Accelerometer Beat control

@description @boardname@ guitar: using accelerometer to control tempo

~avatar avatar

Use the Accelerometer to control guitar tempo

Concepts:
- Gravity
- Acceleration
- X, Y, Z coordinates
- Tempo
- Beat
- Mapping
- Graphing
- Absolute value

~

Duration: 30 - 45 minutes

accelerometer controlled tempo
https://youtu.be/kA0HpqCWsjs

Blocks

input.acceleration(Dimension.Y)
music.setTempo(120)
pins.map(0, 0, 1023,60, 320)
Math.abs(1)

Accelerometer, gravity and tilting!

The @boardname@ contains an accelerometer sensor that is able to measure forces applied to the board. On earth, we are subject to the gravity force which pulls us to the ground!

https://youtu.be/0SULoTKmkhI

When the @boardname@ is flat on a table, with the screen pointing up, the gravity force is aligned with the Z axis of the @boardname@.

If you tilt it up and down, the force will align with the Y axis -- this is how we can detect tilting!!! If the force along Y grows, the @boardname@ is tilting more and more vertically!

Measuring Acceleration along different coordinates (X, Y, Z axis)

The acceleration block approximately measures milli-g, which is 1/1000 of a g or the acceleration of gravity.

Step 1: Graphing acceleration

basic.forever(() => {
    led.plotBarGraph(input.acceleration(Dimension.Y), 1023)
})

Create the code that measures the change in the Y axis acceleration as a graph on the LEDs

Dowload the code to the @boardname@

Test the movements that move the graph from 1 to 5 bars on the LEDs

Extra

Try graphing the acceleration along the X and Z axis. Can you explain the differences?

~hint

Mapping

It is common to map one standard to another - such as with temperature

~

Step 2: Mapping acceleration to Beat

@boardname@ sensors produce signal values between 0 to 1023. The map block converts the signal to a desired range.

basic.forever(() => {
        music.setTempo(pins.map(Math.abs(input.acceleration(Dimension.Y)),
            0, 1023,
            60, 320))
         music.playTone(Note.C, music.beat(BeatFraction.Quarter));
})

Create the code that Maps Y axis acceleration as tempo

Download the code to the @boardname@ on the guitar

Test the movements that speed and slow the tempo

Step 3: Combine with light sensor tone control

Put it all together!

basic.forever(() => {
        music.setTempo(pins.map(Math.abs(input.acceleration(Dimension.Y)),
            0, 1023,
            60, 320))
        music.playTone(
            input.lightLevel() * 25,
            music.beat(BeatFraction.Quarter)
        );
})

Combine the code above with the light sensor tone control code from the previous activity