pxt-calliope/docs/projects/voting-machine.md
Sam El-Husseini e3975e65e5 pxt-microbit Accessibility PR (#529)
* Accessibility changes
2017-09-07 13:42:08 -07:00

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# Voting Machine
## ~ avatar
Build a voting machine using many @boardname@s!
## ~
https://youtu.be/77HOqf8BaNg
In this project, a **voter** program is uploaded on the player's @boardname@. The player uses the buttons to vote ``yes`` or ``no``
and the vote is sent to the **dashboard** @boardname@ via radio.
The dashboard allocates one LED per player and turns it on or off based on the vote.
## The voter program
Assuming button ``A`` is no and ``B`` is yes, the voter program works as follows:
* when button ``A`` is pressed, a number ``0`` is sent via radio and the ``X`` symbol is shown on the screen.
```block
input.onButtonPressed(Button.A, () => {
radio.sendNumber(0)
basic.showIcon(IconNames.No)
})
```
* when button ``B`` is pressed, a number ``255`` is sent via radio and the ``Y`` symbol is shown on the screen.
```block
input.onButtonPressed(Button.B, () => {
radio.sendNumber(255)
basic.showIcon(IconNames.Yes)
})
```
* In order to track the votes, we tell the radio to also transmit the device serial number.
```block
radio.setTransmitSerialNumber(true)
```
* we arbritrarily choose ``4`` as the group used for the communications
```block
radio.setGroup(4)
```
Combined together, the voter program looks as follows:
```blocks
input.onButtonPressed(Button.A, () => {
radio.sendNumber(0)
basic.showIcon(IconNames.No)
})
input.onButtonPressed(Button.B, () => {
radio.sendNumber(255)
basic.showIcon(IconNames.Yes)
})
radio.setGroup(4)
radio.setTransmitSerialNumber(true)
basic.showIcon(IconNames.Ghost)
```
## The dashboard
The dashboard code can be found at [/examples/radio-dashboard](/examples/radio-dashboard).
Download the code from that example into the @boardname@ that will be used to display the result.
When the dashboard receives a message from a @boardname@, it find a pixel for that board (and remembers it)
and uses the number received as the brightness of the LED.
When a message hasn't been received by a board for some time, it's pixel will start to blink. After more time, it will simply turn off.
```package
radio
```