--------------------------------------------------------------------------------- |-- Module : System.Hardware.Arduino.SamplePrograms.Distance-- Copyright : (c) Levent Erkok-- License : BSD3-- Maintainer : erkokl@gmail.com-- Stability : experimental---- Measuring distance using a HC-SR04 sensor. (Data sheet: <http://www.micropik.com/PDF/HCSR04.pdf>.)---- NB. As of March 2 2013; StandardFirmata that's distributed with the Arduino-App does /not/ support the high-- accuracy pulse-in command, which is needed for this sketch. However, there is a patch to add this-- command; see: <http://github.com/rwldrn/johnny-five/issues/18> for details on how to install it. You /should/-- have this patched version of Firmata running on your board for this sketch to function properly.---- Accuracy: Keep in mind that measurements on a platform like Arduino is always subject to-- various errors. Relying on this program for precise distance measurements would be a mistake.-- The results here should be accurate to within about half-a-centimeter, provided you stay-- within the range of HC-SR04, which is between 2 to 400 cm. For anything more precise than-- this, you'll need to use a much more sensitive sensor.-------------------------------------------------------------------------------moduleSystem.Hardware.Arduino.SamplePrograms.DistancewhereimportControl.Monad(forever)importControl.Monad.Trans(liftIO)importNumeric(showGFloat)importSystem.Hardware.Arduino -- | Sound travels 343.2 meters per second (<http://en.wikipedia.org/wiki/Speed_of_sound>).-- The echo time is round-trip, from the sensor to the object and back. Thus, if echo is high-- for @d@ microseconds, then the distance in centimeters is:---- @-- d * 10^-6 * 343.2 * 10^2 / 2-- = 1.716e-2 * d-- @microSecondsToCentimeters ::Int->FloatmicroSecondsToCentimeters :: Int -> Float
microSecondsToCentimeters Int
d =Float
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d -- | Measure and display the distance continuously, as reported by an HC-SR04 sensor.---- Wiring: Simply connect VCC and GND of HC-SR04 to Arduino as usual. The @Echo@ line on the sensor is connected-- to Arduino pin 2. The @Trig@ line is connected on the board to the @Echo@ line, i.e., they both connect to the-- same pin on the Arduino. We also have a led on pin 13 that we will light-up-- if the distance detected is less than 5 centimeters, indicating an impending crash!---- <<http://github.com/LeventErkok/hArduino/raw/master/System/Hardware/Arduino/SamplePrograms/Schematics/Distance.png>>distance ::IO()distance :: IO ()
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