Haskell-Nxt is a library to control Lego Mindstorms NXT Bricks from Haskell.
Since the nature of the communication with the Brick is stateful, the library consists almost entirely of monads.
Haskell-NXT is my first piece of Haskell software and probably has a lot of rough edges still so comments, tips, bug reports or patches are very much appreciated.
I want to briefly explain the architecture of the Library here.
This module is used for setting up a NXTBrick and fiddling around with it. Mainly for testing purposes
Contains various Enums and Translations between NXT protocol bytecodes and descriptive strings or haskell types.
Various helper functions for converting bytestrings, converting little- to big-endian integers, dissecting messages etc.
Lowest level communication with NXT Bricks. Provides a wrapper around System.IO calls to make top-level programs a little less noisy and basic read/write commands
Implementations of the most common Direct Commands in two parts each.
One function to assemble the message to send to the Brick, one action
to send the message to the Brick in the IO Monad
A custom class
Appendable is used to more easily combine various data types
into NXT messages.
High-level library on top of NXT.Commands to easily run and stop motors.
High-level library on top of NXT.Commands to easily read out the sensors. Requires an initialization call after opening the connection to the Brick and assumes that the sensors are plugged into their intended ports on the brick.
Since the Ultrasonic sensor communicates with the NXT via I2C, controlling it is a little more complicated. This module contains mainly a list of I2C commands.
btBrick = NXTBrick Bluetooth "/dev/tty.NXT-DevB-1" main = do h <- nxtOpen btBrick playtone h 500 500 setupDefaultSensors h s <- getDistance h putStrLn (show s) nxtClose h
This opens a NXT Brick located as a serial device at /dev/tty.NXT-DevB-1 in Bluetooth mode (as opposed to USB, which isn't implemented yet). The brick is opened, plays a tone and reads the distance from the distance sensor.
- The library works only on POSIX systems currently.
- It was developed on Mac OSX 10.5 with GHC 6.8.3 and uses some GHC-extensions to the Haskell standard.
- Communication with Bricks via USB isn't implemented yet.
- I2C delay
- Implement USB interface
- Implement the rest of the NXT Commands
- Debugging helpers
- Reading Tony Busers Ruby-Nxt library has greatly helped understanding the NXT protocol, especially controlling the Ultrasonic Sensor http://rubyforge.org/projects/ruby-nxt/
- The Lego Mindstorms Bluetooth Developer Kit nicely described the protocol http://mindstorms.lego.com/Overview/NXTreme.aspx
- The Labview for NXT Advanced Programming Guide contained some hints that were missing from the Lego docs