Unit testing embedded and Arduino projects
When you’ve got more than the simplest embedded program for Arduino (or any other framework), it becomes much harder to test that it’s working properly by purely running it. For something like Blink, testing is simple because all we need to do is upload it and see the LED turn on and off; there’s little risk of missing anything significant. However, let’s skip forward to a menu based application with Serial or Ethernet control, there is very little chance that you’d catch all the edge cases by manual testing.
Timed blink - IO Abstraction library example
Timed blink is a version of well known Arduino blink example that is shipped with the standard IDE, but is redesigned to use the Abstraction and timer library. Example circuit for the code is exactly the same a blink, and if you use the inbuilt LED pin (which it does by default) then there’s no need to build any circuit whatsoever. Instead of using delay() calls to set the duration of the led flash, it uses the task management library to schedule a task.
IOA I2C/Wire abstraction that works Across Arduino and mbed
IoAbstraction 2.0 onwards has core I2C/Wire functionality provided by several functions, these abstract the use of I2C over Arduino and mbed, and over time the implementation of these will be improved, such that asynchronous behaviour will be possible on certain boards. Prior to 2.0, we had conditional I2C code scattered around the project, but now nearly all such functionality is separated out by platform, and sometimes even by board, we’ve made this available through the API, so you can use it too.
Simple Collection - btree list
IoAbstraction contains a very simple collection that is relatively lightweight and works on a wide range of boards. It is a btree list that provides ordering and list storage. It works on anything from Arduino Uno upwards! It’s memory usage is very configurable, and the way it resizes arrays is also configurable too. You can set the initial size if you know how many items to expect, and do not wish for it to resize, or you can rely on platform defaults, for more general purpose cases.
Simple Collection - Thread safe circular buffer
Circular buffer provides an easy way to interact with events that take place on another thread or in an interrupt, it is not very efficient when used on a single thread because it uses atomic operations to ensure consistency of the buffer. It is an advanced collection for use by users that understand threading and writing interrupt safe code. There are two implementations, an optmized version for storing bytes, and a generic version that can be used to store any type, the generic version can also be created as a memory pool, where it works slightly differently.
Task Manager Low Power example for SAMD boards
There are often cases when you’ll need to run a micro controller from a battery power source. Unlike when running from mains power, every milli-amp matters. In these cases IoAbstraction’s task manager is able to integrate easily with most low power libraries. Task manager works by repeatedly calling the runLoop() function within loop() or main, during each loop task manager evaluates if any tasks are yet ready to run, and if they are it runs them.
Stabilising an existing Arduino or embedded product
Sometimes the situation arises where a product is built (or gets close to being built), before any concerns about it’s stability are discussed or proper planning arranged. Often this leads to code being written without any proper test plan in place. Combined with very tight deadlines there’s often even no plan to go back and fix things up. Once this situation occurs, it’s probable that the product release will be compromised.
Rotary encoder with non-polling (interrupt based) switches from PCF8574
IoAbstraction has full support for interrupts on most devices, meaning we can connect a Rotary Encoder to an Arduino using a standard PCF8574 IO expander chip. In order to do this we need the PCF8574 /INT line to be connected to an Arduino pin that supports interrupts (such as pins 2 or 3). Further, you can also have switches handle push button input without polling, by initialising for interrupt, especially useful with IO exapnders.
IoAbstraction: Using a matrix keyboard / keypad
Matrix keyboards are arranged such that the keys are in a matrix of rows and columns. This means that instead of needing a spare input for each key, one INPUT for each column and one OUTPUT for each row is all that’s needed. In order to use the keyboard, we create a class of type MatrixKeyboardManager and configure it with an IoAbstractionRef, a KeyboardLayout that describes the keyboard attached (there are some standard ones already defined) and a listener that will be informed of changes.
Getting started Unit testing with Arduino platform
This article discusses how to unit test a simple project with Arduino, if you’re not used to writing unit tests, or need more background, then first read this guide on unit testing embedded projects. Presently, all our testing using a custom test framework that is built into IoAbstraction, it can be considered as the least number of components that implement a test framework. It works pretty well overall, we wrote this because we needed the testing to work on all Arduino boards, and even mbed boards too.
