Problems installing COM3 serial port

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3 total messages Started by Daryl Sayers Mon, 30 Jun 1997 00:00

#362

Author: Daryl Sayers
Date: Mon, 30 Jun 1997 00:00

26 lines
1823 bytes


I have 2 onboard 16550 serial ports that have been working great. I need
to install a third port so I got a basic 8250 seial card and installed this
card as COM1 I then moved the 2 onboard serial ports to COM2 and COM3.
I know all the hardware is working correctly by themselves.
I have connected:

ttyS0 Testing (COM1 8250 serial card IRQ 4 at 3F8)
ttyS1 Modem   (COM2 16550 onboard serial IRQ 3 at 2F8)
ttyS2 Mouse   (COM3 16550 onboard serial IRQ 4 at 3E8)

When I boot all 3 are recognised by the BIOS and then by the linux probe.
I can then use the modem and send data out the testing port. Both ttyS0
and ttyS1 work correctly.
It only when I run X that my problem shows up. Under X, the mouse works
and the modem works.
When sending data out the testing port (ttyS0) it is VERY slow but not
corrupt. A single character is sent about every 10seconds. Too my
amazement when I moved the mouse the data then got sent. It seems that
when the mouse (ttyS2 Irq 4) generates an interupt the service routine
also checks the Transmit buffer of ttyS0 also at Irq 4.
Reading the Serial Howto it seems I should be able to share interupts
like this so what else have I missed. 
Even though the Linux probe finds the seial ports correctly I still
use setserial to make sure the ports are configured correctly.

Re: Problems installing COM3 serial port

#360

Author: M. Buchenrieder
Date: Tue, 01 Jul 1997 00:00

46 lines
2374 bytes

Daryl Sayers <daryl@stonemicro.com.au> writes:


>I have 2 onboard 16550 serial ports that have been working great. I need
>to install a third port so I got a basic 8250 seial card and installed this
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>card as COM1 I then moved the 2 onboard serial ports to COM2 and COM3.

[...]

>ttyS0 Testing (COM1 8250 serial card IRQ 4 at 3F8)
                                      ^^^^^
>ttyS1 Modem   (COM2 16550 onboard serial IRQ 3 at 2F8)
>ttyS2 Mouse   (COM3 16550 onboard serial IRQ 4 at 3E8)
                                          ^^^^^

[...]
>When sending data out the testing port (ttyS0) it is VERY slow but not
>corrupt. A single character is sent about every 10seconds. Too my
>amazement when I moved the mouse the data then got sent. It seems that
>when the mouse (ttyS2 Irq 4) generates an interupt the service routine
>also checks the Transmit buffer of ttyS0 also at Irq 4.

And that's exactly what Linux is telling you.

>Reading the Serial Howto it seems I should be able to share interupts
>like this so what else have I missed. 

Read again. It explicitely states that you can NOT do this, unless
you're using a multiport card that knows how to share IRQs between several
devices, or do some soldering on the ISA bus yourself. The standard
PC's hardware architecture is broken where it comes to IRQ sharing
on the ISA bus.

>Even though the Linux probe finds the seial ports correctly I still
>use setserial to make sure the ports are configured correctly.

Put the first serial port on an interrupt of its own.

Michael
-- 
   Michael Buchenrieder * mibu@scrum.muc.de / mibu@scrum.greenie.muc.de 
**************************************************************************
Portable, adj.:
                          Survives system reboot.

Re: Problems installing COM3 serial port

#361

Author: George Durbridge
Date: Wed, 02 Jul 1997 00:00

22 lines
1442 bytes

M. Buchenrieder (mibu@scrum.muc.de) wrote:

<discussion of irq conflict snipped>
: 
: Put the first serial port on an interrupt of its own.
: 

If that doesn't work and you have an interrupt to spare, get a bus mouse &
card.  You used to have to recompile to include bus mouse support, but I
don't think that's true any more. 

: Michael
: -- 
:    Michael Buchenrieder * mibu@scrum.muc.de / mibu@scrum.greenie.muc.de 
: **************************************************************************
: Portable, adj.:
:                           Survives system reboot.
-- 
/* George Durbridge, Melbourne, Victoria, Australia */
/* tel 61 (03) 9280 3390      fax 61 (03) 9280 3355 */
/* gdurb@melbourne.dialix.com.au                    */

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