pxt-calliope/docs/lessons/charting/activity.md

charting activity

Measure the acceleration on the micro:bit in the "z" direction.

~avatar avatar

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!

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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.

radio.sendNumber(input.acceleration(Dimension.X));

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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.

basic.forever(() => {
    radio.sendNumber(input.acceleration(Dimension.X));
});

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We want to register code to run when a packet is received over radio. We can implement this code by adding on data received.

basic.forever(() => {
    radio.sendNumber(input.acceleration(Dimension.X))
})
radio.onDataReceived(() => {
    
})

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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.

basic.forever(() => {
    radio.sendNumber(input.acceleration(Dimension.X))
})
radio.onDataReceived(() => {
    led.plotBarGraph(radio.receiveNumber(), 1023)
})

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Notice that moving the micro:bit the farthest direction in the x direction will be -1023 on the charting beneath the simulator. The second observation will be that the LEDs will be full brightness on the 2nd micro:bit. There is a single LED turned on with the 1st micro:bit. Additionally, the graphs will reflect 0 acceleation for the 1st micro:bit. In this scenario, if you are adjusting the acceleration in the simualator, you are also changing your chart that will be produced.

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NOTE: The colors of the charts reflect the color of the micro:bit simulator. In this instance, the micro:bits are blue and green. So the colors of the line graphs reflect the colors of the micro:bit

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After running this simulatation several seconds by moving the micro:bit side to side in the x direction, you are ready to graph or chart the accceleration of the micro:bit. We want a printout of our acceleration on Excel. We will graph the fluctuating acceleration of the simulation experiment.

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Finally, you must open the Excel CSV file by clicking on the data.xls file that was downloaded to Downloads Folder.

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Have fun reviewing your simulation and analyze the acceleration by chart the Excel data using Excel.

• 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!
• Review and analyze the actual micro:bit device acceleration data on Excel