Full difference between ttyS* and cua* devices?

Full difference between ttyS* and cua* devices?

Post by bp » Fri, 12 May 2000 04:00:00



What are the full differences between using the ttyS* and cua*
devices?  I understand the ttyS devices can supply "canonical" I/O
and that they are used primarily for modem, but that's about it.

I ask because I ran into a problem with some GPS software I
am writing, where it would not work with ttyS1 but worked as
expected with cua1.

What tcsetattr() incantation is required to get ttyS* to
behave as a cua*?  Where can I find more detailed information
about this (the Serial and Serial-Programming HOWTOs don't
go into full detail on the differences).

thanks,
-bpb

 
 
 

Full difference between ttyS* and cua* devices?

Post by Paul Kimo » Fri, 12 May 2000 04:00:00



> What are the full differences between using the ttyS* and cua*
> devices?  I understand the ttyS devices can supply "canonical" I/O
> and that they are used primarily for modem, but that's about it.
>   Where can I find more detailed information
> about this (the Serial and Serial-Programming HOWTOs don't
> go into full detail on the differences).

Ted Ts'o wrote a message to the linux-kernel mailing list:
  http://kernelnotes.org/lnxlists/linux-kernel/lk_9803_02/0814.html
Is it useful to you?

--


 
 
 

Full difference between ttyS* and cua* devices?

Post by Villy Kru » Sat, 13 May 2000 04:00:00



Quote:>What are the full differences between using the ttyS* and cua*
>devices?  I understand the ttyS devices can supply "canonical" I/O
>and that they are used primarily for modem, but that's about it.

>I ask because I ran into a problem with some GPS software I
>am writing, where it would not work with ttyS1 but worked as
>expected with cua1.

The difference is that ttyS is sensitive to the DCD pin whereas
cua is not.  Also when one cua device is open all other attemtp
to open that device or the corresponding ttyS is blocked, that is,
you get exclusive access.

Villy

 
 
 

Full difference between ttyS* and cua* devices?

Post by bp » Sat, 13 May 2000 04:00:00


| >   Where can I find more detailed information
| > about this (the Serial and Serial-Programming HOWTOs don't
| > go into full detail on the differences).
|
| Ted Ts'o wrote a message to the linux-kernel mailing list:
|   http://kernelnotes.org/lnxlists/linux-kernel/lk_9803_02/0814.html
| Is it useful to you?

Thanks Paul!  That was the perfect article for what I was seeking.

The code changes are easy enough, I'll just have to add the fcntl()
and other termio flags to get it to work.

Thanks again,
-Brent

 
 
 

1. Difference between cua and ttyS

This seems like an obvious question, but I don't find a definitive
description in any of the docs.

What exactly is the difference between /dev/ttyS<n> and /dev/cua<n>?
I.e. device majors 4 and 5.

In the course of reading c.o.l.* over the weeks I've seen people
having problems with a tty advised to try using the cua instead, as well as
the converse, and "see if that fixes it".  :-)

Since I am frequently plugging one serial thing into another, I'd like
to operate from a position of knowledge rather than trial and error -
so can anyone provide a thorough and correct description of the
difference between these two devices?

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