PC104 Serial Port Programming

You haven't really given enough information. In what way doesn't it work? Can you see the hardware? Does transmit work? Does receive work? Are you using interrupts?

Andrew

COM1 and COM3 share an interrupt, as also COM2 and COM4.

Your drivers have to be able to handle the situation, and there is some special programming needed to avoid losing interrupt requests with an edge-sensitive PIC set-up (as the PC is using due to the timer).

If you can get an IBM PC Technical Manual, the handling is described there.

HTH

Thanks for asking...

Let me first give you some background information on what I am attempting to do. I am using the PC104 board serial ports to... read in GPS position coordinates from a GPS on one serial port, read in measurements from a temperature sensor on another serial port, take these two data strings and combine them, and then via another serial send them to an amateur radio modem for transmission. Now as I said before I can get COM3 (temp sensor) and COM4 (GPS) to read in correctly however when I attempt to use COM1 or COM2 nothing happens. I would also like to add that my temp sensor is powered by the serial port and when it is connected to COM3 or COM4 the power LED illuminates (thus showing that at least something is happening). I have noticed that the difference between the serial ports on my PC and on the PC104 is that on the PC104 when I connect my temp sensor the led light automatically comes on without running my code. However, on my PC, the power light is off until my code is executed. When my code finishes the light goes back off. This ofcourse is not the case with the PC104 board. The power LED is ON constantly when the temp sensor is pluged into COM3 and COM4 and always off when I connect it to COM1 and COM2 (thus showing it is receiving no power. I have tried to connect COM2 to my PC and transmit some characters however this does not work, nor does the receive. I am not using interupts, and to be completely honest all I know about interupts is the word "interupts" itself. Perhaps this is my problem, could you possibly elaborate on this or atleast direct me to something that would easily explain this topic. I do not have a computer science background, I am just stuborn and like to learn things I know nothing about. I hope this helps, just let me know if you have any more questions.

It sounds as if you are not setting modem control lines correctly. If you haven't read them, these two web pages are a useful guide as to how to use and program serial ports on the PC:

If you read through those, and the code samples, then that may shed light on your problem. Perhaps if you read those and then "report back"?

Andrew

Is your application reading and writing directly to the UART registers? IIRC, the built-in UART I/O ports are not at the same addresses as they are in a PC.

What operating system are you using on the PC104 platform and is this a different operating system than the one used on your PC and when you tried to connect COM2 to my PC and transmit some characters, did you use a null modem cable. Also, have you used known good software to rule out the hardware as the problem.

#Example of QNX Neutrino serial port setup /sbin/devc-ser8250 -u1 3f8,4 -u2 2f8,3 -u3 280,5 -u4 288,5

Look in the BIOS. You can't share an IRQ between ports. Your IRQs should look something like this example from my project.

COM1, Port 3f8-3ff, IRQ 4 COM2, Port 2f8-2ff, IRQ 3 COM3, Port 3e8-3ef, IRQ 10 COM4, Port 2e8-2ef, IRQ 11

Peter