April 2015
Beginner to intermediate
346 pages
6h 18m
English
Content preview from BeagleBone Cookbook
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Chapter 8. Real-Time I/O
8.0 Introduction
Sometimes, when BeagleBone Black interacts with the physical world, it needs to respond in a timely manner. For example, your robot has just detected that one of the driving motors needs to turn a bit faster. Systems that can respond quickly to a real event are known as real-time systems. There are two broad categories of real-time systems: soft and hard.
In a soft real-time system, the real-time requirements should be met most of the time, where most depends on the system. A video playback system is a good example. The goal might be to display 60 frames per second, but it doesn’t matter much if you miss a frame now and then. In a 100 percent hard real-time system, you can never fail to respond in time. Think of an airbag deployment system on a car. You can’t even be 50 ms late.
Systems running Linux generally can’t do 100 percent hard real-time processing, because Linux gets in the way. However, the Bone has an ARM processor running Linux and two additional 32-bit programmable real-time units (PRUs [http://bit.ly/1EzTPZv]) available to do real-time processing. Although the PRUs can achieve 100 percent hard real-time, they take some effort to use.
This chapter shows several ways to do real-time input/output (I/O), starting with the effortless, yet slower BoneScript and moving up with increasing speed (and effort) to using the PRUs.
Note
In this chapter, as in the others, we assume that you are logged in as root (as indicated by the
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.