C

Using a shift register to control eight digital outputs with three GPIO lines on the Raspberry Pi

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.

Categories: software development, C, embedded computing, Raspberry Pi

Using an I2C analog-to-digital converter chip with the Raspberry Pi, from the ground up

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.

Categories: Raspberry Pi, electronics, embedded computing, C

Using an I2C analog-to-digital for temperature measurement on the Raspberry Pi

This article describes how to do simple temperature measurement with a Raspberry Pi, and I2C analog-to-digital converter, and a thermistor.

Categories: Raspberry Pi, electronics, embedded computing, C

Using the Qpid Proton C++ library to understand AMQP

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.

Categories: C, middleware

Using media keys in a Linux console application

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.

Categories: Linux, C, embedded computing

Running CP/M on the Raspberry Pi Pico microcontroller

This article introduces CPICOM -- an emulator for CP/M 2.2 on the Raspberry Pi microcontroller.

Categories: retrocomputing, Pico, C, Z80

Getting back into C programming for CP/M

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.

Categories: retrocomputing, C, Z80

Getting back into C programming for CP/M -- part 2

Using the 1989 HI-TECH C compiler on CP/M, and some general observations about CP/M programming with real hardware.

Categories: retrocomputing, C, Z80

cwordle -- A Wordle-like word-guessing game for CP/M

Building a CP/M implementation of the notorious Wordle game.

Categories: retrocomputing, C, Z80

Using the FreeType library to render text nicely onto a Linux framebuffer

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.

Categories: software development, C, Linux, embedded computing, Raspberry Pi

Embedding resources into executables built using GCC

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.

Categories: software development, C

Why 'int x = 0' is uninitialized data to the GNU C compiler

An oddity of the GCC C compiler that can lead to strange results, particularly in an embedded application

Categories: C, embedded computing

The importance of enabling compiler warnings in C and C++ programming

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.

Categories: software development, C

Building native graphical applications in C for MS Windows, using GTK+ and open-source tools

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.

Categories: software development, C

Using ImageMagick to generate anti-aliased bitmap fonts for a microcontroller's LCD display

This article describes how to generate and use compressed, anti-aliased font data, for use in a microcontroller application.

Categories: C, Linux, embedded computing, Pico

Developing KCalc-CPM -- a scientific calculator utility for CP/M

My first CP/M program for nearly 40 years -- how, and why, I wrote it.

Categories: retrocomputing, C, Z80

Building a custom mechanical keyboard from scratch

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.

Categories: Arduino, embedded computing, C

Conway's Game of Life in 3D perspective

Implementing a program to run Conway's cell population simulation, using a 3D perspective view on the Linux framebuffer.

Categories: software development, C, Linux

Using the Linux framebuffer in C/C++ -- just the essentials

The absolute minimum information needed to start using the Linux framebuffer as a graphical display in C/C++ applications.

Categories: software development, C, Linux, embedded computing

Using the Linux framebuffer in C/C++ -- just the essentials (part 2)

This article continues my original framebuffer just the essentials article, by describing how to handle less straightforward framebuffer configurations.

Categories: software development, C, Linux, embedded computing

Building a Lua extension library for Linux in C/C++

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.

Categories: software development, Lua, C

Getting reasonably robust proximity measurements from an ultrasonic sensor on the Raspberry Pi

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.

Categories: software development, C, embedded computing, Raspberry Pi

Monitoring an INA219 chip in a Raspberry Pi battery-backed power supply

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.

Categories: software development, C, embedded computing, Raspberry Pi

Using an HD44780 LCD display module with the Raspberry Pi, from the ground up

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.

Categories: software development, C, embedded computing, Raspberry Pi

The costs and benefits of software pulse-width modulation on the Raspberry Pi

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.

Categories: software development, C, embedded computing, Raspberry Pi

Using the Maxim DS3231 I2C real-time clock in C on the Raspberry Pi Pico

The Maxim DS3231 I2C real-time clock is a reasonably accurate, inexpensive device, that is easy to interface to the Raspberry Pi Pico.

Categories: C, embedded computing, Pico

Controlling a chain of MAX7219 LED matrices using C on a 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.

Categories: software development, C, embedded computing, Pico

Raspberry Pi Pico: loading code into RAM and running it -- part 1

This is the first of (at least) two articles on loading and running arbitrary executable code into RAM on the Pico, and running it.

Categories: C, embedded computing, Pico

Raspberry Pi Pico: loading code into RAM and running it -- part 2

This is the second of (at least) two articles on loading and running arbitrary executable code into RAM on the Pico, and running it.

Categories: C, embedded computing, Pico

Some thoughts on using a USB keyboard with the Raspberry Pi Pico

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.

Categories: software development, C, embedded computing, Pico

Using flash memory as non-volatile storage on the Pi Pico microcontroller

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.

Categories: software development, C, Linux, embedded computing, Pico

Using Linux command-line tools for programming the SparkFun Pro Micro microcontroller (and similar)

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.

Categories: Arduino, embedded computing, C

Building and programming a USB keypad from the ground up

The first step towards designing and building a custom keyboard, from the very first principles, using an Arduino-type microcontroller.

Categories: Arduino, embedded computing, C

C-to-parallel IC

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.

Categories: software development, C, Linux, embedded computing, Arduino

Comparing a natively-compiled Java webservice with C

Implementing a webservice in C and Java, to see which performs better in terms of throughput and resource usage.

Categories: software development, Java, C

Converting a floating-point number to a fraction (approximately) using continued fraction expansion

A detailed description of a method for performing this common numerical conversion, with C source code.

Categories: mathematics, C

Some thoughts on a DS1302 real-time clock board for RC2014/Z80 and CP/M

Constructing and programming a real-time clock board for my Z80 CP/M system

Categories: C, electronics, Z80, retrocomputing

Exchanging files between an SC130 CP/M board and a Linux 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.

Categories: C, electronics, Z80, retrocomputing

C development for Linux without a standard library

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.

Categories: software development, C, embedded computing