ble - Bluetooth Low Energy for Haskell

ble is a Haskell library for writing Bluetooth Low Energy peripherals (and soon centrals).

For usage, see the haddocks. There are also examples in examples directory.

Example

The code below is a simple example of a complete Bluetooth Low Energy application. The application allows a counter to be read, and adds one to the value of the counter, as well as allowing the counter to be set to any value.

module Main (main) where

import Bluetooth
import Control.Concurrent     (threadDelay)
import Control.Concurrent.STM
import Control.Monad.IO.Class

main :: IO ()
main = do
  ref <- newTVarIO 0
  conn <- connect
  x <- runBluetoothM (registerAndAdvertiseApplication $ app ref) conn
  case x of
    Right _ -> putStrLn "Started BLE counter application!"
    Left e -> error $ "Error starting application " ++ show e
  threadDelay maxBound

app :: TVar Int -> Application
app ref
  = "/com/turingjump/example/counter"
     & services .~ [counter ref]

counter :: TVar Int -> Service
counter ref
  = "4f1f704f-0a0b-49e4-bd27-6368f27697a7"
     & characteristics .~ [getCounter ref]

getCounter :: TVar Int -> CharacteristicBS
getCounter ref
  = "90874979-563e-4224-9da6-3b1a6c03e97d"
      & readValue  ?~ encodeRead readV
      & writeValue ?~ encodeWrite writeV
      & properties .~ [CPRead, CPWrite]
  where
    readV :: Handler Int
    readV = liftIO $ do
      v <- atomically $ modifyTVar' ref succ >> readTVar ref
      putStrLn $ "Value requested. New value: " ++ show v
      return v

    writeV :: Int -> Handler Bool
    writeV i = liftIO $ do
      v <- atomically $ swapTVar ref i
      putStrLn $ "Value changed to: " ++ show i
      putStrLn $ "Old value: " ++ show v
      return True

Requirements

ble currently only supports Linux, and requires Bluez versions 5.41 and up. To see what version you are running, type:

bluetoothd --version