larson demo.swift

// Demo from live coding demo on Twitter.
// Swift for Arduino. Arduino UNO native code, using Grove 'neopixel' stick.
// Gives the effect of the scanner on 'K.I.T.T.' from Knight Rider.
//
// Libraries: iLEDHelpers.swift
//------------------------------------------------------------------------------

import AVR
typealias IntegerLiteralType = Pin

let ledPin = 4
let pixels = 10
let delayTime: MS = 60
var forward = true

pinMode(pin: ledPin, mode: OUTPUT)

var buffer = iLED_Setup_Buffered(pin: ledPin, count: pixels, hasWhiteChip: false)

func fadeUnlitPixels(litPixel: UInt8) {
    // fade the pixels that have already been illuminated
    for j in 0..<pixels {
        if j != litPixel {
            // this is a naughty hack but will work...
            // we are playing with the internal implementation of
            // iLEDFastColor, this needs exposing properly
            buffer[Int(j)] = (buffer[Int(j)] / 3) & 0xff00
        }
    }
}

while true {
    if forward {
        for i in 0..<pixels {
            buffer[Int(i)] = iLEDRed
            fadeUnlitPixels(litPixel: i)
            iLEDFastWriteBuffer()
            delay(milliseconds: delayTime)
        }
        forward = false
    } else {
        for i in stride(from: pixels&-1, to: 0, by: -1) {
            buffer[Int(i)] = iLEDRed
            fadeUnlitPixels(litPixel: i)
            iLEDFastWriteBuffer()
            delay(milliseconds: delayTime)
        }
        forward = true
    }
}