16550a baud_base < 9600 ???

16550a baud_base < 9600 ???

[Horváth Ákos Péter]

Hi all,

I need to use serial communication with baud rates under 9600. I tried the 
uart 16550a linux driver, but found that setserial gives back invalid 
argument. The cause is that serial_core.c and 8250.c explicitly disallow 
these settings. Why?

The quick & dirty solution (simply eliminating these limit checks in 
serial_core.c and 8250.c) does GPF. Ok :)

Is it possible now to do serial communication with a device which can only 
1200 baud?

thanks,

MaXX

Re: 16550a baud_base < 9600 ???

[Theodore Ts'o]

On Mon, Aug 29, 2005 at 03:05:56PM +0200, Horv?th ?kos P?ter wrote:
> Hi all,
> 
> I need to use serial communication with baud rates under 9600. I tried the 
> uart 16550a linux driver, but found that setserial gives back invalid 
> argument. The cause is that serial_core.c and 8250.c explicitly disallow 
> these settings. Why?
> 
> The quick & dirty solution (simply eliminating these limit checks in 
> serial_core.c and 8250.c) does GPF. Ok :)
> 
> Is it possible now to do serial communication with a device which can only 
> 1200 baud?

You don't need to edit the serial driver to use baud rates under 9600.
The baud_base argument is not what is used to set the baud rate; it is
used to indicate the clock crystal in the serial card utilized to
calculate the baud rate divisor which is programmed into the UART
given a specific required baud rate. 

If you are using setserial to set the baud rate, you're using the
wrong tool, and you're misunderstanding what you need to do.

Use the stty command to set the baud rate on a port.

						- Ted