Reading data from /dev/ttyS0

[Bill Moseley <moseley@hank.org>]

I'm trying to get a program that reads serial data working.  I'm looking
for some debugging tips.

I've got an X10 mouse-remote (JR20 RF remote,and JR21A receiver).  I was
using it on a Windows machine to run winamp.  Now I'm trying to get it
to work with linux.  It's a remote control for controlling the mouse,
but also has a number of other buttons.  It looks like a universal
remote control.

The receiver can plug into a PS2 or serial port.  On my windows machine
I plugged it into a serial port.  I've now plugged it into my serial
port on the Debian machine.

It seems like the serial port is receiving data:

$ cat /proc/tty/driver/serial
serinfo:1.0 driver:5.05c revision:2001-07-08
0: uart:16550A port:3F8 irq:4 baud:9600 tx:3332 rx:1951 brk:1381
RTS|CTS|DTR

Click a few buttons on the remote and the counts change:

$ cat /proc/tty/driver/serial
serinfo:1.0 driver:5.05c revision:2001-07-08
0: uart:16550A port:3F8 irq:4 baud:9600 tx:3359 rx:1969 brk:1390
RTS|CTS|DTR

So that tells me that the hardware is working.  

My understanding of devices in linux is quite fuzzy.  I'm using a
program by Kevin Boone called mouse_remoted that reads from the device,
looks at the character codes and then writes the mouse specific data to
/dev/mouse_remote, and the other data to /dev/pc_remote.  The idea is
you have a program that reads from /dev/pc_remote that controls things
(like volume and start/stop/pause for xmms).

By default, the program reads from /dev/mouse.  On my machine that is:

  wxrwxrwx    1 root root   7 Feb 24 12:05 /dev/mouse -> gpmdata

  prw-r--r--   1 root root    0 Apr 10 11:58 /dev/gpmdata


But, I'm connected to the serial port, so I changed the program to read
from /dev/ttyS0 and recompiled.

    crw-rw-r--    1 root dialout 4,  64 Jan 24 08:26 /dev/ttyS0

The program starts, and claims it's reading, but then nothing happens. 
The program is not complicated, but it does use threads, which I'm not
familiar with.  

First it opens /dev/ttyS0:
    fi = open (MOUSE, O_RDONLY | O_NOCTTY);

then later.

BYTE readByte(int fi)
        {
        char buf[2];
printf("About to read a byte\n");
        read (fi, buf, 1);
printf("Read %02x\n", buf[0]);
        return buf[0];
        }

It hangs after saying "About to read a byte" in this function.  So the
read() is blocking.

So, ah, well, any suggestions??

Is there an easy way to dump the chars from /dev/ttyS0? 

Thanks,

-- 
Bill Moseley


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