ttyUSB sendbreak problem

ttyUSB sendbreak problem

[Jean-Denis Girard]

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Hi list,

I'm writing a program which communicates via modem with an embedded
device (electrical network monitoring). The frames are terminated by a
BREAK.

My program works fine when I use a Cyclades 8Yo multiports card, but
fails using USB to serial adapters (tried with pl2303 and FTDI
converters). I suspect that the BREAK are not passed correctly, but I
don't have equipment to check.

I've tried with:
 tcsendbreak(modem,0);
 ioctl(modem, TCSBRK,0);
 ioctl(modem, TCSBRKP, 0);

- From pl2303 debug mode, I see that pl2303_break_ctl is called:
 drivers/usb/serial/pl2303.c: pl2303_break_ctl - port 0
 drivers/usb/serial/pl2303.c: pl2303_break_ctl - turning break on
 drivers/usb/serial/pl2303.c: pl2303_write_bulk_callback - port 0
 drivers/usb/serial/pl2303.c: pl2303_send - port 0
 drivers/usb/serial/pl2303.c: pl2303_break_ctl - port 0
 drivers/usb/serial/pl2303.c: pl2303_break_ctl - turning break off

I found a few references of similar problems in the past, but it was for
older kernels (I'm using 2.6.28.4), so the question remains: should it
work or is there a known problem sending BREAK using ttyUSB?


Thanks,
- --
Jean-Denis Girard

SysNux                  Systèmes  Linux  en Polynésie française
http://www.sysnux.pf/   Tél: +689 50 10 40 / GSM: +689 79 75 27
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Re: ttyUSB sendbreak problem

[Thiago Galesi]

And in this case BREAK is which character?? 0x00?

Anyway, take a look at the stty options and man termios (even though
they may do what your IOCTL is doing)

Also explain what's happening exactly: what does "but
> fails using USB to serial adapters" mean.




On Mon, Feb 16, 2009 at 8:29 PM, Jean-Denis Girard <jd.girard@sysnux.pf> wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Hi list,
>
> I'm writing a program which communicates via modem with an embedded
> device (electrical network monitoring). The frames are terminated by a
> BREAK.
>
> My program works fine when I use a Cyclades 8Yo multiports card, but
> fails using USB to serial adapters (tried with pl2303 and FTDI
> converters). I suspect that the BREAK are not passed correctly, but I
> don't have equipment to check.
>
> I've tried with:
>  tcsendbreak(modem,0);
>  ioctl(modem, TCSBRK,0);
>  ioctl(modem, TCSBRKP, 0);
>
> - From pl2303 debug mode, I see that pl2303_break_ctl is called:
>  drivers/usb/serial/pl2303.c: pl2303_break_ctl - port 0
>  drivers/usb/serial/pl2303.c: pl2303_break_ctl - turning break on
>  drivers/usb/serial/pl2303.c: pl2303_write_bulk_callback - port 0
>  drivers/usb/serial/pl2303.c: pl2303_send - port 0
>  drivers/usb/serial/pl2303.c: pl2303_break_ctl - port 0
>  drivers/usb/serial/pl2303.c: pl2303_break_ctl - turning break off
>
> I found a few references of similar problems in the past, but it was for
> older kernels (I'm using 2.6.28.4), so the question remains: should it
> work or is there a known problem sending BREAK using ttyUSB?
>
>
> Thanks,
> - --
> Jean-Denis Girard
>
> SysNux                  Systèmes  Linux  en Polynésie française
> http://www.sysnux.pf/   Tél: +689 50 10 40 / GSM: +689 79 75 27
> -----BEGIN PGP SIGNATURE-----
>
> iEYEARECAAYFAkmZ9sgACgkQuu7Rv+oOo/iFuQCeJSaxikghrQhjS68WKU0Hc//7
> wZQAn2XMnmunfW2avO/uPFQDrw+s9INO
> =AB0j
> -----END PGP SIGNATURE-----
> --
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-- 
-
Thiago Galesi

Re: ttyUSB sendbreak problem

[Greg KH]

On Mon, Feb 16, 2009 at 01:29:12PM -1000, Jean-Denis Girard wrote:
> Hi list,
> 
> I'm writing a program which communicates via modem with an embedded
> device (electrical network monitoring). The frames are terminated by a
> BREAK.
> 
> My program works fine when I use a Cyclades 8Yo multiports card, but
> fails using USB to serial adapters (tried with pl2303 and FTDI
> converters). I suspect that the BREAK are not passed correctly, but I
> don't have equipment to check.

Odd, pl2303 should support break just fine.

> I've tried with:
>  tcsendbreak(modem,0);
>  ioctl(modem, TCSBRK,0);
>  ioctl(modem, TCSBRKP, 0);
> 
> From pl2303 debug mode, I see that pl2303_break_ctl is called:
>  drivers/usb/serial/pl2303.c: pl2303_break_ctl - port 0
>  drivers/usb/serial/pl2303.c: pl2303_break_ctl - turning break on
>  drivers/usb/serial/pl2303.c: pl2303_write_bulk_callback - port 0
>  drivers/usb/serial/pl2303.c: pl2303_send - port 0
>  drivers/usb/serial/pl2303.c: pl2303_break_ctl - port 0
>  drivers/usb/serial/pl2303.c: pl2303_break_ctl - turning break off
> 
> I found a few references of similar problems in the past, but it was for
> older kernels (I'm using 2.6.28.4), so the question remains: should it
> work or is there a known problem sending BREAK using ttyUSB?

It should work, but your specific device might not support the break
control (some seem to and others don't.)  It's a very cheap device.

You might want to try a more expensive device, like the io networks
devices, break on them should work just fine as they have a "real" uart
device within them.

good luck,

greg k-h