Ok here is my problem...

I have 4 serial ports on my system. ttyS0 and ttyS2 share IRQ 4, and ttyS1 and ttyS3 share IRQ 3.

The ports all work fine if I

echo "testdev0" >> /dev/ttyS0
echo "testdev1" >> /dev/ttyS1
echo "testdev2" >> /dev/ttyS2
echo "testdev3" >> /dev/ttyS3

Now, if I load a touchscreen driver that monitors ttyS1, when I try and echo data to ttyS3 (which shares an interrupt....) the data gets there eventually after a long delay. This usually indicates and problem sharing interrupts or an interrupt clash (after much reading of the excellent Serial HOWTO).

I have another custom program that monitors the rs232 ports. When this is loaded the interrupts seem to all go wrong as well.

If there was an interrupt problem I would expect to see it from when the system is started up... not just from when a program is loaded that opens the rs232 port.

My question is, what would cause a program to break the interrupts on an rs232 port?

onyx^; a little research says voltage via cable is sensitive. check those cables. lenght have a constaint. try a loopback tester to find where problem
may be.

i dont think its an electronics problem on that scale. It is more a problem somewhere in the bios --> kernel ---> serial setup ---> program type... chain of events that is causing the problem, I just don't know where....

(i have used the cables testing the program on development machine where interrupts / serial works fine and this is not a problem.)

onyx; U R correct. rereading original post,
it maybe as u noted this last post, overlooked those interrupt & irq,s recheck serial setup & irq,s addresses.
not sure about bios however check them
& program + kernel as last resort. got to be in there somewhere? good hunting!

penguin4 -- can you please provide a detailed, step-by-step description of exactly what you are recommending be done to investigate and solve the reported issue? I'm sorry but I simply do not understand what technical advice you are offering here. Please elaborate with further details, preferably in the form of a set of commands that could be run. Thanks -- J.W.

jw; no am not offering techincal advice.
just pointing where solutions maybe found. if notice poster,s have no idea where to look for answers. that is all am attempting to help with!

penguin4 - I realize you are trying to help, but if you are going to make suggestions about how to solve a particular technical problem, your advice should be based on your own personal experience and/or knowledge, which you believe will likely lead to a solution. Simply replying to a post by suggesting that a solution will be found by "looking around" at things does not meet those standards. That's sort of like just telling people that no matter what their question is, it can be solved by doing a Google search.

All I am asking of you is that if you are going to reply to a post, that your response include specific, clear, step-by-step comments. Vague, non-specific comments do not help anybody. -- J.W.