pxt-calliope/docs/lessons/charting/activity.md
2016-03-25 16:47:20 -07:00

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# charting activity
Measure the acceleration on the micro:bit in the "z" direction.
### ~avatar avatar
To create a new script, go to the [Create Code](/microbit/create-code) page and tap `New Project` under `Block Editor`.
### ~
Welcome! This activity will teach how to use the 1st micro:bit to chart the second micro:bit's acceleration in the "x" direction. Let's get started!
Let's measure `acceleration (mg)` and then `send number`. `Acceleration` is measured in **milli-gravities**, so a value of -1000 is equivalent to -1g or -9.81m/s^2. We will be able to get the acceleration value (g-force), in the specified "x" dimension. `Send number` will broadcast a number data packet to other micro:bits connected via radio.
```blocks
radio.sendNumber(input.acceleration(Dimension.X))
```
We want to display the acceleration forever. In order to do so, we need a `forever` loop. A forever loop will repeat code in the background forever.
```blocks
basic.forever(() => {
radio.sendNumber(input.acceleration(Dimension.X))
})
```
We want to register code to run when a packet is received over radio. We can implement this code by adding `on data received`.
```blocks
basic.forever(() => {
radio.sendNumber(input.acceleration(Dimension.X))
})
radio.onDataReceived(() => {
})
```
Finally, we want to chart the acceleration. So we must first implement `plot bar graph`. `Plot Bar Graph` will display a vertical bar graph based on the value and high value. In order to transfer the receive the number from the 1st micro:bit, we must implement `receive number` to constantly display a vertical bar graph based on the value. Remember, the value will equal to the micro:bit's acceleration in the "x" direction.
```blocks
basic.forever(() => {
radio.sendNumber(input.acceleration(Dimension.X))
})
radio.onDataReceived(() => {
led.plotBarGraph(radio.receiveNumber(), 1023)
})
```
* Connect the first micro:bit to your computer using your USB cable and run the charting script on it.
* Connect the second micro:bit to your computer using your USB cable and run the charting script on it.
* The first person and second person take turns tilting the micro:bit in the "x" direction while the other player charts the data on the micro:bit!