pxt-calliope/docs/projects/voting-machine.md
2017-11-20 11:46:36 -08:00

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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 loaded onto a player's @boardname@. The player uses the buttons to vote either``yes`` or ``no``
and the vote is sent to a **dashboard** @boardname@ using the 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 for a NO vote and ``B`` is for YES, the voter program works like this:
### Transmit a NO vote
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)
})
```
### Transmit a YES vote
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)
})
```
### Set device serial number
In order to track the votes, we tell the radio to also transmit the device serial number.
```block
radio.setTransmitSerialNumber(true)
```
### Set the radio group
We arbitrarily choose ``4`` as the group used for the communications.
```block
radio.setGroup(4)
```
Combined together, the final voter program is this:
```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 is in the [radio dashboard](/examples/radio-dashboard) example.
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
```