[Haskell-cafe] Serial Communications in Haskell
ronguida at mindspring.com
Tue Aug 28 22:19:37 EDT 2007
I'm on a Windows box and I'm looking for a way to talk to a serial
port (for example, RS-232) from Haskell. I couldn't find a library to
do this, so I am wondering how to create one.
I have a fairly thorough understanding of how to open and use a serial
port with the Windows API. In particular, to open a serial port, I
have to use CreateFile, which is the same API call that opens files.
In fact, if I call openFile from GHC, and pass "COM1:" as the
filename, then I can get a writable serial port.
> module Serial
> import System.IO
> main = do
> h <- openFile "COM1:" ReadWriteMode
> hPutStrLn h "Hello World"
I can't read from the port (I always get an immediate EOF), and I have
no way of configuring things like the baud rate or the parity
settings. Nevertheless, this demonstrates that openFile can at least
open the serial port.
What I would like to do is create some functions that would allow me
to open and configure a serial port, and get a Handle back so that I
can use the existing IO functions like hGetChar and hPutChar. I am
assuming that hGetChar eventually calls win32::ReadFile and hPutChar
eventually calls win32::WriteFile. These same two API calls would
work for serial ports.
In Windows, there are 23 API functions that apply specifically to
serial ports. Out of these 23 functions, only a few of them are
actually necessary if I just want to send and receive data.
Of course, I don't know how to call Windows API functions from Haskell,
and I have no idea how to hook things to the IO library so that I can
use a Handle for a serial port. I'm looking for some advice on how to
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