pxt-calliope/docs/projects/voting-machine.md

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.

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.

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.

radio.setTransmitSerialNumber(true)

• we arbritrarily choose 4 as the group used for the communications

radio.setGroup(4)

Combined together, the voter program looks as follows:

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.

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.