MCP3008.swift

A Swift library for the MCP3008 10-bit SPI ADC

Summary

This simple library reads the values produced by the MCP3008 10 bits SPI-driven ADC. This component is able to convert analog signals (with a voltage range defined by Vref, most of the times you’ll connect Vref and Vdd to 5V) to an integer value between 0 and 1023. ADCs are extremely useful for example for boards like the RaspberryPis that don’t have their own analog input pins (like Arduinos or traditional embedded boards).

Supported Boards

Every board supported by SwiftyGPIO: RaspberryPis, BeagleBones, C.H.I.P., etc…

To use this library, you’ll need a Linux ARM board with Swift 3.x/4.x.

The example below will use a RaspberryPi 2 board but you can easily modify the example to use one the the other supported boards, a full working demo projects for the RaspberryPi2 is available in the Examples directory.

Usage

The first thing we need to do is to obtain an instance of SPIInterface from SwiftyGPIO and use it to initialize the MCP3008 object:

import SwiftyGPIO
import MCP3008

let spis = SwiftyGPIO.hardwareSPIs(for:.RaspberryPi2)!
let spi = spis[0]
let m = MCP3008(spi)

Then just use readValue to read the current converted value (0…1023) from one of the analog inputs:

m.readValue(0) //CH0 pin

Reading a value from an unconnected channel (floating input) will give meaningless values, so, be sure to read from the right input.

The library also support virtual spis using bit-banging:

let gpios = SwiftyGPIO.GPIOs(for:.RaspberryPi2)
var cs = gpios[.P27]!
var mosi = gpios[.P22]!
var miso = gpios[.P4]!
var clk = gpios[.P17]!

var spi = VirtualSPI(mosiGPIO: mosi, misoGPIO: miso, clockGPIO: clk, csGPIO: cs)

let m = MCP3008(spi)

for i in 0...7 {
    print("Value for channel ",i,": ",m.readValue(for: i) << 1) //Shift required to obtain the correct value
}

Installation

Please refer to the SwiftyGPIO readme for Swift installation instructions.

Once your board runs Swift, if your version support the Swift Package Manager, you can simply add this library as a dependency of your project and compile with swift build:

  let package = Package(
      name: "MyProject",
      dependencies: [
    .Package(url: "https://github.com/uraimo/MCP3008.swift.git", majorVersion: 2),
    ...
      ]
      ...
  ) 

The directory Examples contains sample projects that uses SPM, compile it and run the sample with ./.build/debug/TestMCP.

If SPM is not supported, you’ll need to manually download the library and its dependencies:

wget https://raw.githubusercontent.com/uraimo/MCP3008.swift/master/Sources/MCP3008.swift https://raw.githubusercontent.com/uraimo/SwiftyGPIO/master/Sources/SwiftyGPIO.swift https://raw.githubusercontent.com/uraimo/SwiftyGPIO/master/Sources/Presets.swift https://raw.githubusercontent.com/uraimo/SwiftyGPIO/master/Sources/SPI.swift https://raw.githubusercontent.com/uraimo/SwiftyGPIO/master/Sources/SunXi.swift  

And once all the files have been downloaded, create an additional file that will contain the code of your application (e.g. main.swift). When your code is ready, compile it with:

swiftc *.swift

The compiler will create a main executable.