Re: belkin usb serial converter (mct_u232), break not working

[Thomas Stewart <thomas@stewarts.org.uk>]

On Wednesday 20 October 2004 22:22, you wrote:
> Try replacing ioctl(fd, TCSBRK, 0) with
> ioctl(fd, TCSBRKP, duration)
> duration is in 100ms units, so try 10 or 20.
>
> Or you can use tcsendbreak(fd, duration);
> I'm not sure of the units for this function on Linux
> manpage says 'implementation defined',
> a book I have says 250ms units in Linux.

I've tyred various combinations of ioctl(fd, TCSBRKP, x) and tcsendbreak(fd, 
x), where x is 2, 5, 10, 20 and 200.

One thing I did notice is that no mater what the value I use, it always 
finishes very quickly, there does not appear to be any duration.

take porttest.c:
#include <sys/fcntl.h>
#include <sys/ioctl.h>
main(int argc, char ** argv) {
        int fd = open(argv[1], O_RDWR|O_NOCTTY);
        ioctl(fd, TCSBRKP, 20);
        close(fd);
}

$ time ./porttest /dev/ttyS0
real    0m2.001s
user    0m0.001s
sys     0m0.000s

A standard serial port with a 2 second break (20*100ms), takes as expected 
just over 2 seconds.

$ time ./porttest /dev/ttyUSB1
real    0m0.004s
user    0m0.000s
sys     0m0.001s

However with the USB converter instead, it takes 5 ms to complete. Much 
shorter than expected.

Is it a driver issue?

Regards
-- 
Tom

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