Serial port library

[Bram Roelandts]

Hi

I've been using Luvit for quite some time and it's a great fit for my project. Sadly though, there's no serial port library available at the moment. Since I really need the serial port, I was hoping you guys could give me a few pointers.

I've come across a thread from 2016 about serial support (https://groups.google.com/d/msg/luvit/m_bJes9J2p0/u2hi21_4CQAJ), but I was unable to run the posted gists. Someone apparently did get the serial port working, but didn't open-source it. The guy said they used "a mixture of Luvit, C and FFI. FFI for read and write, C for line monitoring threads and Luvit (uv.poll for events on the port)", which already gives a basic idea.

I'm quite comfortable working with Luvit by now, but I lack knowledge to write a library myself using libuv and FFI. How would I go about this? Should I read up on libuv and FFI and try to hack something together? What are some good resources to get started? I'm eager to learn, but I simply wouldn't know where to start on this one.

Thanks in advance!

Kind regards,

Bram

[Tim Caswell]

It's not too hard with FFI.  The closest docs are this article: http://luvit.io/blog/pty-ffi.html

At a past job, I did a lot of serial stuff with luvit.  Luckilly, it's open source and can be found at https://github.com/kubos/kubos/blob/15f8bd97c080d1f34c8b2cf93c9cfcecb7571e9a/services/communication-service/libs/termios-serial.lua

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[Tim Caswell]

Using is fairly simple, you just open the serial device using the built-in fs and run the ffi functions on the FD:

    local fd = assert(fs.open(device, mode))

    set_termio(fd, baud)

https://github.com/kubos/kubos/blob/15f8bd97c080d1f34c8b2cf93c9cfcecb7571e9a/services/communication-service/libs/transport-serial.lua#L39-L40

[Bram Roelandts]

Thanks a lot for the open-source serial library! 

While trying to run it, however, I ran into a problem with fs. I'm unsure whether I'm supposed to use coro-fs or the standard luvit fs, but neither of them works without error. I've posted the code I'm using and the errors I'm getting on GitHub: https://gist.github.com/brammahh/2b70dfefb7728d7d9e712cdee410ba45

Your help is really appreciated!

[Tim Caswell]

The transport code is a kubos specific thing, I just meant it as an example.

The coro error you're getting is because you can't use coroutine libraries on the main thread.  Either use Lua's coroutine.create or coroutine.wrap.

[Bram Roelandts]

Coroutine.wrap indeed did the job. After some fiddling with hardware level conversion, I was able to test the example you provided and it works like a charm. Thanks for your help, and also for the wide variety of Luvit code you open-sourced on GitHub! It really helps as a reference.