We’re going to be walking through how to prepare a Yocto build for use with our i.MX6 products, specifically the TS-4900 which we have a special build recipe for. A build recipe is a friendly term to describe the scripts and environment variables required to build a Yocto distribution. There are many other build recipes available which work on a more generic level as well, so this guide can be applied generally as well. This guide is both an echo and extension of the TS-4900 Build Yocto Distribution wiki page. I’ll be mostly echoing (aka copy/pasting) the steps, but I’ll also add a few notes along the way. I’m going to assume you’ve landed here because you’re using search terms that make you at least familiar with what Yocto is and the terminology that surrounds a basic software development environment. If you have questions, I’m happy to try and answer them in the comments that follow.
Here are some tips compiled from our seasoned engineers on what they wish they’d known about embedded linux back when they were “newbs”. Newcomers and seasoned veterans alike should get some good nuggets of information and possibly a fun perspective looking back at our own humble beginnings. We’ll try not to overwhelm you as we make our way through the list. We’re not here to rewrite the books, but do want to provide a personal perspective. If you’re in the camp of people who’ve been using desktop Linux, just be aware embedded Linux is a different animal, especially when it comes to space constraints, different CPU architecture (ARM), resilience to sudden power outages, and inability to install any mainline Linux kernel or distribution you please. And maybe you’re in the microprocessor camp moving towards a more generalized and capable embedded Linux system. Either way, we’ll assume you have at least some knowledge of Linux as we walk through this guide.
Tag jumping is immensely helpful when developing in a CLI environment such as Vim or Emacs. Simply place a marker over the function, variable, class, macro, etc. and with a keystroke jump to the declaration or view other references across multiple files. This productivity tool will help you develop and debug faster and get a better understanding of your codebase.
There are two main solutions for tag jumping: ctags and cscope. Both are very similar in how they function: scan a codebase and index keywords (tags) and their locations. Vim understands the index and provides you with an interface for jumping back and forth between the tags.
The differences between the two are small, but important to distinguish. With ctags, you can use autocomplete (aka omnicomplete) for function and variable names as you type, something cscope doesn’t give you. Also, there’s much less setup to get ctags up and running as it’s generally already installed. The downside is ctags doesn’t do as well as cscope with a conglomerated or mostly unknown codebase. The good news is, they can co-exist!
We’re going to take a look at setting up and basic usage of both in this guide. If you need a diverse codebase to try this out on, try cloning a random trending c repository from GitHub. I settled on grpc/grpc because it was large and varied enough to really put ctags and cscope to the test.
The question “How do I write a TS Image to an SD card under Linux / Mac OSX / Windows?” comes up quite a bit when dealing with embedded systems or any situation where you want to make an exact, bit-by-bit copy of a removable storage card or disk. While the following guide talks about our products, it can be applied generically. Read through it first to make sure you have a basic, core understanding of the instructions given, and then apply them to your situation. We’ll be looking at how to write to an entire disk and/or a specific partition on that disk using the
dd command, a common utility found in most unix systems for low-level operations on hard disks. Jokingly, ‘dd’ stands for “disk destroyer” or “delete data”, so take care!
Here’s an example program our engineers might find useful. Kris Bahnsen, a long time engineer for Technologic Systems, wrote this simple program to get the voltage input (Vin) on the 8 – 28 VDC power rail on the TS-7670 (Rev. D or later) or TS-7400-V2 (Rev. B or later). Without going into too much detail about implementation of the on-board supervisory microcontroller, there is a register which is used to store various ADC values, including Vin. This example program basically polls this 4 byte register via I2C interface, accounts for the voltage divider (see TS-7670 schematic or TS-7400-V2 schematic), and spits out the Vin value. So, without further ado, here’s the code:
We’re graduating from our Getting Started with Qt Creator on the TS-TPC-8390-4900 guide, where we ran an example program which came preloaded with Qt Creator on our TS-TPC-8390-4900, and moving into a more real world situation. This guide builds upon the foundations that we set up in the getting started guide and will walk you through building a simple human machine interface (HMI) for supervisory control and data acquisition (SCADA) applications. We’ll be controlling a register connected to a red LED as well as reading a temperature sensor connected to our CPU. This is about as basic as you can get to demonstrate both system control and data acquisition, and it’s not far from a basic real world use case. In the real world, you’d be toggling DIO or relays instead of toggling an LED. As an end user of the touch panel computer (TPC), you’d be transferring control signals or other data via RS-232 or Ethernet with the press of a button. Once you complete this tutorial it’s a small jump to toggle DIO and relays to control a remote system.
For this guide, a project file containing TS-TPC-8390-4900 specific code written in C++ called “HeatLaser” will be provided for you. It reads CPU temperature every second and toggles the red LED. You’ll simply download it and open the project within Qt Creator. By the end of this guide, you’ll be able to run and have a basic understanding of a Qt Quick Controls application. When you’re comfortable, you can make some edits to the project file to implement other similar tasks that may be more relevant to your needs.
Let’s take a quick look at an example C++ program which reads CPU temperature and controls an LED using sysfs. This example is a bit specific in that it’s only been tested on our NXP i.MX6 powered TS-4900 or TS-7970 running Yocto Linux, but the principles could be applied to other embedded systems as well. If you’re interested in the nitty gritty details about sysfs, take a look at The sysfs Filesystem by Patrick Mochel. Suffice it to say for our purposes, sysfs makes it easy for us to interact with system hardware using plain text files located in the /sys/ directory. The file to control the red LED is /sys/class/leds/red-led/brightness. The file to read the CPU temperature is /sys/class/thermal/thermal_zone0/temp. If we want to turn the red LED on, we simply write a ‘1’ to the file, and not surprisingly, writing a ‘0’ will turn it off. If you’ve booted up your TS-4900 or TS-7970, you can see this by running the shell commands:
In this getting started guide, we’re going to look at what it takes to get an example Qt Creator project running on the TS-TPC-8390-4900 or TS-TPC-7990. This will help pave the way for developing a human machine interface (HMI) for supervisory control and data acquisition (SCADA). We’ll start out by talking about the expected workflow and specific versions compatible with our chosen hardware, TS-TPC-8390-4900 or TS-TPC-7990. Next the TS-TPC-8390-4900 and Qt Creator will need to be prepared to work together. Finally, we’ll test our environment by running an example Qt Quick Controls Application. In a follow up guide, titled Develop a Simple Qt Quick Interface for HMI/SCADA Applications, we’ll look into what it takes to gather some system data and control DIO.
This guide will walk you through the basic steps of getting your TS-TPC-8390-4900 touch panel computer (TPC) up and running. It’s mostly an extrapolation from the official TS-TPC-8390-4900 Manual, but provides a more practical approach in setting up common connections, networking, and environments to begin development. We’ll assume you’ve already gone through the excitement of unboxing, and we’ll pick up from there.
Let’s get our TS-TPC-8390-4900 hooked up! This includes our very basic connections we’ll need for most any development or project: power, serial console, Ethernet, and optionally a keyboard and mouse.