Analog.hs

-------------------------------------------------------------------------------
-- |
-- Module      :  System.Hardware.Arduino.SamplePrograms.Analog
-- Copyright   :  (c) Levent Erkok
-- License     :  BSD3
-- Maintainer  :  erkokl@gmail.com
-- Stability   :  experimental
--
-- Reads the value of an analog input, controlled by a 10K potentiometer.
-------------------------------------------------------------------------------

module System.Hardware.Arduino.SamplePrograms.Analog where

import Control.Monad       (when)
import Control.Monad.Trans (liftIO)

import System.Hardware.Arduino

-- | Read the value of an analog input line. We will print the value
-- on the screen, and also blink a led on the Arduino based on the
-- value. The smaller the value, the faster the blink.
--
-- The circuit simply has a 10K potentiometer between 5V and GND, with
-- the wiper line connected to analog input 3. We also have a led between
-- pin 13 and GND.
--
--  <<http://github.com/LeventErkok/hArduino/raw/master/System/Hardware/Arduino/SamplePrograms/Schematics/Analog.png>>
analogVal :: IO ()
analogVal = withArduino False "/dev/cu.usbmodemfd131" $ do
               setPinMode led OUTPUT
               setPinMode pot ANALOG
               cur <- analogRead pot
               liftIO $ print cur
               go cur
  where led = pin 13
        pot = pin 17 -- NB. Analog-3 is pin 17 on the UNO
        go cur = do digitalWrite led True
                    delay cur
                    digitalWrite led False
                    delay cur
                    new <- analogRead pot
                    when (cur /= new) $ liftIO $ print new
                    go new