Question

I am writing a C program that will read and write from/to a serial port. Each write will be followed by a read which will contain data based on the write. I will have about 16 different writes to perform, each followed by a read.

I am still new to serial programming and am trying to determine how to approach this. Should the program block during each write/read (basically having a big while(1) loop of writes and reads)?

Is it possible to have one thread sending writes while another thread performs the reads? Can a callback be created for allowing a thread to know when data is available to be read from the serial port?

Thanks for the help.

Edit:

OS: Linux

Answer 1

It sounds like a simple loop with a read and a write will be enough. If you want more control (like writing a keep-alive after X seconds of no input) use select or poll; they allow you to “sense” if data is available, so a read will not block (however, you should still read non-blocking in case something happens between the select and the read). Multithreading doesn’t make sense in this case.

select and poll also allow you to test if writing will block; again, write non-blocking just to be sure. You generally don’t want your process to be hanging in some blocking system call, ever, apart from select or poll, that is. (at least, I don’t)

Use ioctl to set various parameters on the serial line. Use

$ strace -o /tmp/strace.minicom -f minicom

to launch minicom (or any other terminal program) and see what they do to get things working, if you’re stuck. And as always, see man select/poll/read/ioctl for more information.