Q: serial port transmit pending count

[Grant Edwards]

In article <3de40f51$1 at news.nz.asiaonline.net>, Colin Brown wrote:

> I am using pySerial to talk to serial ports under Mandrake
> Linux. Does anyone know of a way to find the remaining
> bytecount awaiting transmission please? I tried getting the
> size from the file descriptor but with no luck.

How did you try to get it from the file descriptor?

TIOCOUTQ returns the number of buffered tx chars.  For some
drivers (e.g. 16x50 UARTS) it doesn't appear to include
characters in the hardware FIFO.  For some others, I know it
does.

 import termios,fcntl,struct

 def txCount(fd):
    s = fcntl.ioctl(fd,termios.TIOCOUTQ,TIOCM_zero_str)
    return struct.unpack('I',s)[0]

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