System.RaspberryPi.GPIO

Library for controlling the GPIO pins on a Raspberry Pi (or any system using the Broadcom 2835 SOC). It is constructed as a FFI wrapper over the BCM2835 library by Mike McCauley.

Data types

data Pin

This describes the pins on the Raspberry Pi boards. Since the BCM2835 SOC internally uses different numbers (and these numbers differ between versions, the library internally translates this pin number to the correct number.

Constructors

Pin03

Pins for the P1 connector of the V2 revision of the Raspberry Pi

Pin05

Pin07

Pin08

Pin10

Pin11

Pin12

Pin13

Pin15

Pin16

Pin18

Pin19

Pin21

Pin22

Pin23

Pin24

Pin26

Pin36

PinP5_03

Pins for the P5 connector of the V2 revision of the Raspberry Pi

PinP5_04

PinP5_05

PinP5_06

PinV1_03

Pins for the P1 connector of the V1 revision of the Raspberry Pi

PinV1_05

PinV1_07

PinV1_08

PinV1_10

PinV1_11

PinV1_12

PinV1_13

PinV1_15

PinV1_16

PinV1_18

PinV1_19

PinV1_21

PinV1_22

PinV1_23

PinV1_24

PinV1_26

Instances

Eq Pin

Methods

(==) :: Pin -> Pin -> Bool

(/=) :: Pin -> Pin -> Bool

Show Pin

Methods

showsPrec :: Int -> Pin -> ShowS

show :: Pin -> String

showList :: [Pin] -> ShowS

data PinMode

A GPIO pin can be either set to input mode, output mode or an alternative mode.

Constructors

Input

Output

Alt0

Alt1

Alt2

Alt3

Alt4

Alt5

Instances

Enum PinMode

Methods

succ :: PinMode -> PinMode

pred :: PinMode -> PinMode

toEnum :: Int -> PinMode

fromEnum :: PinMode -> Int

enumFrom :: PinMode -> [PinMode]

enumFromThen :: PinMode -> PinMode -> [PinMode]

enumFromTo :: PinMode -> PinMode -> [PinMode]

enumFromThenTo :: PinMode -> PinMode -> PinMode -> [PinMode]

Eq PinMode

Methods

(==) :: PinMode -> PinMode -> Bool

(/=) :: PinMode -> PinMode -> Bool

Show PinMode

Methods

showsPrec :: Int -> PinMode -> ShowS

show :: PinMode -> String

showList :: [PinMode] -> ShowS

type LogicLevel = Bool

Either high or low.

type Address = Word8

This describes the address of an I2C slave.

data SPIBitOrder

Specifies the SPI data bit ordering.

Constructors

LSBFirst

MSBFirst

data SPIPin

This describes which Chip Select pins are asserted (used in SPI communications).

Constructors

CS0

CS1

CS2

CSNONE

Instances

Enum SPIPin

Methods

succ :: SPIPin -> SPIPin

pred :: SPIPin -> SPIPin

toEnum :: Int -> SPIPin

fromEnum :: SPIPin -> Int

enumFrom :: SPIPin -> [SPIPin]

enumFromThen :: SPIPin -> SPIPin -> [SPIPin]

enumFromTo :: SPIPin -> SPIPin -> [SPIPin]

enumFromThenTo :: SPIPin -> SPIPin -> SPIPin -> [SPIPin]

Eq SPIPin

Methods

(==) :: SPIPin -> SPIPin -> Bool

(/=) :: SPIPin -> SPIPin -> Bool

Show SPIPin

Methods

showsPrec :: Int -> SPIPin -> ShowS

show :: SPIPin -> String

showList :: [SPIPin] -> ShowS

type CPOL = Bool

Clock polarity (CPOL) for SPI transmissions.

type CPHA = Bool

Clock phase (CPHA) for SPI transmissions.

General functions

withGPIO :: IO a -> IO a

Any IO computation that accesses the GPIO pins using this library should be wrapped with this function; ie withGPIO $ do foo. It prepares the file descriptors to devmem and makes sure everything is safely deallocated if an exception occurs. The behavior when accessing the GPIO outside of this function is undefined.

GPIO specific functions

setPinFunction :: Pin -> PinMode -> IO ()

Sets the pin to either Input or Output mode.

readPin :: Pin -> IO LogicLevel

Returns the current state of the specified pin.

writePin :: Pin -> LogicLevel -> IO ()

Sets the specified pin to either True or False.

I2C specific functions

withI2C :: IO a -> IO a

Any IO computation that uses the I2C bus using this library should be wrapped with this function; ie withI2C $ do foo. It prepares the relevant pins for use with the I2C protocol and makes sure everything is safely returned to normal if an exception occurs. If you only use the GPIO pins for I2C, you can do withGPIO . withI2C $ do foo and it will work as expected. WARNING: after this function returns, the I2C pins will be set to Input, so use setPinFunction if you want to use them for output.

setI2cClockDivider :: Word16 -> IO ()

Sets the clock divider for (and hence the speed of) the I2C bus.

setI2cBaudRate :: Word32 -> IO ()

Sets the baud rate of the I2C bus.

writeI2C :: Address -> ByteString -> IO ()

Writes the data in the ByteString to the specified I2C Address. Throws an IOException if an error occurs.

readI2C :: Address -> Int -> IO ByteString

Reads num bytes from the specified Address. Throws an IOException if an error occurs.

writeReadRSI2C :: Address -> ByteString -> Int -> IO ByteString

Writes the data in the ByteString to the specified Address, then issues a "repeated start" (with no prior stop) and then reads num bytes from the same Address. Necessary for devices that require such behavior, such as the MLX90620.

SPI specific functions

withAUXSPI :: IO a -> IO a

Any IO computation that uses the AUX SPI functionality using this library should be wrapped with this function; ie withAUXSPI $ do foo. It prepares the relevant pins for use with the SPI protocol and makes sure everything is safely returned to normal if an exception occurs. If you only use the GPIO pins for SPI, you can do withGPIO . withAUXSPI $ do foo and it will work as expected. WARNING: after this function returns, the SPI pins will be set to Input, so use setPinFunction if you want to use them for output.

withSPI :: IO a -> IO a

Any IO computation that uses the SPI functionality using this library should be wrapped with this function; ie withSPI $ do foo. It prepares the relevant pins for use with the SPI protocol and makes sure everything is safely returned to normal if an exception occurs. If you only use the GPIO pins for SPI, you can do withGPIO . withSPI $ do foo and it will work as expected. WARNING: after this function returns, the SPI pins will be set to Input, so use setPinFunction if you want to use them for output.

chipSelectSPI :: SPIPin -> IO ()

Sets the chip select pin(s). When a transfer is made with transferSPI or transferManySPI, the selected pin(s) will be asserted during the transfer.

setBitOrderSPI :: SPIBitOrder -> IO ()

Set the bit order to be used for transmit and receive. The bcm2835 SPI0 only supports MSBFirst, so if you select LSBFirst, the bytes will be reversed in software. The library defaults to MSBFirst.

setChipSelectPolaritySPI :: SPIPin -> LogicLevel -> IO ()

Sets the chip select pin polarity for a given pin(s). When a transfer is made with transferSPI or transferManySPI, the currently selected chip select pin(s) will be asserted to the LogicLevel supplied. When transfers are not happening, the chip select pin(s) return to the complement (inactive) value.

setClockDividerAUXSPI :: Word16 -> IO ()

Sets the AUX SPI clock divider and therefore the SPI clock speed.

setClockDividerSPI :: Word16 -> IO ()

Sets the SPI clock divider and therefore the SPI clock speed.

setDataModeSPI :: (CPOL, CPHA) -> IO ()

Sets the SPI clock polarity and phase (ie, CPOL and CPHA)

transferAUXSPI :: Word8 -> IO Word8

Transfers one byte to and from the SPI slave. Asserts the CS2 pin during the transfer. Clocks the 8 bit value out on MOSI, and simultaneously clocks in data from MISO. Returns the read data byte from the slave.

transferSPI :: Word8 -> IO Word8

Transfers one byte to and from the currently selected SPI slave. Asserts the currently selected CS pins (as previously set by chipSelectSPI) during the transfer. Clocks the 8 bit value out on MOSI, and simultaneously clocks in data from MISO. Returns the read data byte from the slave.

transferManySPI :: [Word8] -> IO [Word8]

Transfers any number of bytes to and from the currently selected SPI slave, one byte at a time. Asserts the currently selected CS pins (as previously set by chipSelectSPI) during the transfer. Clocks 8 bit bytes out on MOSI, and simultaneously clocks in data from MISO.