A simple and inexpensive shift register can be used to increase the digital output provision of a Raspberry Pi or microcontroller. This well-know technique is easy to apply, but has some limitations that require careful consideration.
This article is about using an I2C analogue-to-digital device for applications like reading sensor values or monitoring backup batteries. With all the technical bits left in.
This article describes how to do simple temperature measurement with a Raspberry Pi, and I2C analog-to-digital converter, and a thermistor.
AMQP is not a trivially-straightforward protocol to understand, but it's necessary to get to grips with it to write effective software that uses the Qpid Proton AMQP library. Perhaps one of the simplest ways to understand AMQP is to use Proton's own packet-tracing features, as this article explains.
Mapping keyboard keys to key codes on Linux is well-documented for the graphical desktop. But what about console applications on embedded Linux systems? There's not much documentation in this area.
This article introduces CPICOM -- an emulator for CP/M 2.2 on the Raspberry Pi microcontroller.
This article is about how programming for CP/M, usng a 40-year-old C compiler, differs from modern C development, even for console applications.
Using the 1989 HI-TECH C compiler on CP/M, and some general observations about CP/M programming with real hardware.
Building a CP/M implementation of the notorious Wordle game.
Writing graphical applications for minimal and embedded Linux systems can present a challenge. One of the problems is producing nicely-rendered text without the facilities that a graphical desktop would provide. This article describes how to use the FreeType library to render text to the Linux framebuffer.
Sometimes it's helpful to be able to create an executable program that embeds all the data it needs, and provide that data as files. C/C++ do not provide any standard way to do this, but GCC has facilities that the developer can use.
An oddity of the GCC C compiler that can lead to strange results, particularly in an embedded application
I see too many C (and C++) programs misbehave at runtime, for reasons that could easily have been detected using checks built into all modern compilers. This article describes some common C programming errors, and shows how they would have been spotted easily if the compiler were configured correctly.
This article describes how to use free, open-source tools to develop graphical applications in C for Microsoft Windows, which run natively. By 'natively' I mean that they don't need any supporting infrastructure (as Cygwin does), and can be packaged and distributed just as any other Windows application, and will look and behave like one.
This article describes how to generate and use compressed, anti-aliased font data, for use in a microcontroller application.
My first CP/M program for nearly 40 years -- how, and why, I wrote it.
There are many kits and plans available for constructing miniature mechanical keyboards. But what do you do if you want a layout the nobody else seems to use? Build it from scratch.
Implementing a program to run Conway's cell population simulation, using a 3D perspective view on the Linux framebuffer.
The absolute minimum information needed to start using the Linux framebuffer as a graphical display in C/C++ applications.
This article continues my original framebuffer just the essentials article, by describing how to handle less straightforward framebuffer configurations.
Lua is an embeddable scripting language, which can be extended in a number of useful ways. This article describes in detail how to create a Lua extension in C (or, with a bit of fiddling, C++) as a loadable (.so) library.
The HC-SR04 proximity sensor is an inexpensive and widely-used ultrasonic device. Connecting one to an HC-SR04 to a Raspberry Pi is a common educational exercise, but getting accurate, repeatable measurement of distance in a real application is actually quite difficult. This article explains why, and what can be done to improve matters.
Many battery-backed power supplies for the Raspberry Pi, and similar systems, use the INA219 current/voltage monitor IC. This device has an I2C interface by which the Pi can determine the battery voltage and current, and estimate the charge level and run-time. This article describes how to write C code that interacts with the INA219.
In this article I explain how to construct, and program in C, an I2C interface to the popular HD44780 LCD display for the Raspberry Pi. Between the article and the accompanying source code, no technical details are concealed: I present the complete hardware design and every line of C code needed to operate it.
The Raspberry Pi doesn't offer much in the way of analog outputs, or even hardware controlled PWM. Software-controlled PWM is an alternative in some applications, but it needs to be used carefully, if inefficiencies are to be avoided.
The Maxim DS3231 I2C real-time clock is a reasonably accurate, inexpensive device, that is easy to interface to the Raspberry Pi Pico.
The MAX7219 IC is widely used to control an 8x8 matrix of LED, but they can be chained to create much larger displays. This article describes how the chaining works, and how to create a driver for the Raspberry Pi Pico.
This is the first of (at least) two articles on loading and running arbitrary executable code into RAM on the Pico, and running it.
This is the second of (at least) two articles on loading and running arbitrary executable code into RAM on the Pico, and running it.
The Pi Pico has USB host support, and can work with a USB keyboard. Although there are some programming examples, the general approach to programming USB host operations is not well documented.
The Pi Pico is an impressive microcontroller for its size and cost, but it lacks specific non-volatile memory. This article explains how to use the program flash ROM for that purpose.
Although building and deploying a simple program to an Arduino board is a point-and-click operation using the Arduino IDE, implementing more complex programs requires more robust build tools. This article describes how to build on Linux using command-line tools -- a process that is nowhere near as easy as it should be. If we can build using command-line tools, we can manage a project using Makefiles and similar techniques.
The first step towards designing and building a custom keyboard, from the very first principles, using an Arduino-type microcontroller.
Make an auxiliary LCD display for a computer that displays data sent to it over a USB connection. Ready-made devices of this sort are widely available, but it's more fun to build your own.
Implementing a webservice in C and Java, to see which performs better in terms of throughput and resource usage.
A detailed description of a method for performing this common numerical conversion, with C source code.
Constructing and programming a real-time clock board for my Z80 CP/M system
This article describes a couple of methods for sharing data and code between a CP/M system with RomWBW BIOS and a Linux system.
There are relatively few good reasons for writing C code without using a standard C library. However, doing so provides valuable insights into how compilers and operating systems work, and is worth doing if only for its educational value.