System.Hardware.Arduino

(The hArduino library is hosted at http://leventerkok.github.com/hArduino/. Comments, bug reports, and patches are always welcome.)

hArduino: Control Arduino from Haskell, using the Firmata protocol.

The hArduino library allows construction of Haskell programs that control Arduino boards that are running the (freely available) Firmata program. Note that hArduino does not allow you to run arbitrary Haskell code on the Arduino! It simply allows you to control a board from Haskell, where you can exchange information with the board, send/receive commands from other peripherals connected, etc.

See http://www.youtube.com/watch?v=PPa3im44t2g for a short video (4m29s) of the blink example.

Running the controller

withArduino

Arguments

:: Bool

If True, debugging info will be printed

-> FilePath

Path to the USB port

-> Arduino ()

The Haskell controller program to run

-> IO ()

Run the Haskell program to control the board:

• The file path argument should point to the device file that is associated with the board. (COM1 on Windows, '/dev/cu.usbmodemfd131' on Mac, etc.)
• The boolean argument controls verbosity. It should remain False unless you have communication issues. The print-out is typically less-than-useful, but it might point to the root cause of the problem.

See System.Hardware.Arduino.Examples.Blink for a simple example.

data Arduino a

The Arduino monad.

Instances

Monad Arduino

Functor Arduino

Applicative Arduino

MonadIO Arduino

Programming the Arduino

Basic handshake with the board

queryFirmware :: Arduino (Word8, Word8, String)

Retrieve the Firmata firmware version running on the Arduino. The first component is the major, second is the minor. The final value is a human readable identifier for the particular board.

Accessing pins

pin :: Word8 -> Pin

Declare a pin on the board by its number.

data Pin

A pin on the Arduino

Instances

Eq Pin

Ord Pin

Show Pin

data PinMode

The mode for a pin.

Constructors

INPUT

Digital input

OUTPUT

Digital output

ANALOG

Analog input

PWM

PWM (Pulse-Width-Modulation) output

SERVO

Servo Motor controller

SHIFT

Shift controller

I2C

I2C (Inter-Integrated-Circuit) connection

Instances

Enum PinMode

Eq PinMode

Show PinMode

setPinMode :: Pin -> PinMode -> Arduino ()

Set the mode on a particular pin on the board

Digital I/O

Writing digital values

digitalWrite :: Pin -> Bool -> Arduino ()

Set or clear a digital pin on the board

Reading digital values

digitalRead :: Pin -> Arduino Bool

Read the value of a pin in digital mode; this is a non-blocking call, returning the current value immediately. See waitFor for a version that waits for a change in the pin first.

pullUpResistor :: Pin -> Bool -> Arduino ()

Turn on/off internal pull-up resistor on an input pin

waitFor :: Pin -> Arduino Bool

Wait for a change in the value of the digital input pin. Returns the new value. Note that this is a blocking call. For a non-blocking version, see digitalRead, which returns the current value of a pin immediately.

waitAny :: [Pin] -> Arduino [Bool]

Wait for a change in any of the given pins. Once a change is detected, all the new values are returned. Similar to waitFor, but is useful when we are watching multiple digital inputs.

waitAnyHigh :: [Pin] -> Arduino [Bool]

Wait for any of the given pins to go from low to high. If all of the pins are high to start with, then we first wait for one of them to go low, and then wait for one of them to go back high. Returns the new values.

waitAnyLow :: [Pin] -> Arduino [Bool]

Wait for any of the given pins to go from high to low. If all of the pins are low to start with, then we first wait for one of them to go high, and then wait for one of them to go back low. Returns the new values.

Analog Communication

Setting up sampling interval

setAnalogSamplingInterval :: Int -> Arduino ()

Set the analog sampling interval, in milliseconds. Arduino uses a default of 19ms to sample analog and I2C signals, which is fine for many applications, but can be modified if needed. The argument should be a number between 10 and 16384; 10 being the minumum sampling interval supported by Arduino and 16383 being the largest value we can represent in 14 bits that this message can handle. (Note that the largest value is just about 16 seconds, which is plenty infrequent for all practical needs.)

Reading analog values

analogRead :: Pin -> Arduino Int

Read the value of a pin in analog mode; this is a non-blocking call, immediately returning the last sampled value. It returns 0 if the voltage on the pin is 0V, and 1023 if it is 5V, properly scaled. (See setAnalogSamplingInterval for sampling frequency.)

Misc utilities

delay :: Int -> Arduino ()

Delay the computaton for a given number of milli-seconds