rtthread

Rtthread is a small Nim library that allows creating a realtime Nim thread.

Why?

Realtime threads are routinely used for realtime digital signal processing such as audio or scientific data, as well as control of analog devices like industrial control or dimming a light or controlling a motor with computer-generated pulse with modulation.

How?

Realtime threads behave just like regular threads, they just receive a special parameter on creation. This library has a thread creation function that sets them up, and after that they can be used like any other Nim thread using the normal stdlib tooling.

Usage

import rtthread, os, posix, posix_utils
var t:Thread[int]

memoryLockAll(MclCurrent)  # prevent swapping

const priority = 94

proc doSomething(x: int) {.thread.} =
  echo x
  sleep 200
  echo x + 1
  sleep 200
  echo x + 2
  sleep 200

createRealtimeThread(t, doSomething, priority, 12345)

echo "started"
joinThread(t)
echo "done"

Setup

Realtime privileges require special access. To just give it a try, run the program as root. To use it regularly, the best way on Linux is to add a group "rt" to your system and add this line to /etc/security/limits.conf:

# /etc/security/limits.conf

@rt -  rtprio     95
@rt -  memlock    unlimited

OS Support

Linux works best, other unixes are also supported. Windows is not supported, but could be, using the similar Windows mechanism. The Industrial Windows version would be interesting to support.

Changelog

0.2.0  Fix void types. Breaking change, needed to change position of priority parameter for this.
0.1.0  Initial