HAL ⁽³⁾

Reusability is an idea often touted in software, and embedded projects are no exception. In fact, the reasons for needing re-usability or ease of porting are often more pertinent to embedded projects even though the initial use-case doesn't call for them, and speed to market is usually business-critical. Why would the processor (or microcontroller) change after it has been designed-in? After all, the hardware designer has to make lots of decisions which are tied to that specific processor in that specific package, so it would be a lot of work for them to change it. Timescales for embedded projects often require the code to be in progress whilst the hardware is being finalised, PCB laid out and prototypes produced. If we can't start the driver layers until the prototypes are available, then it becomes risky to work on the aspects…

Generally, the advice on unit testing in embedded environments is to run your tests on the PC host rather than on the target device. Whilst I agree that this is the most productive arrangement, there are a variety of reasons for needing to test on the target which can be convincing in certain situation. The technique described here allows for both. Mike Long in his GOTO 2015 presentation Continuous Delivery for Embedded Systems says "Test on your host because that's fast - it's a really fast way to develop. But also test on the target because behaviour can change in different ways, different compilers, different hardware..." Niall Cooling in his talk at the EmbeddedOnlineConference 2020 "How agile is changing the face of embedded software development" says (at 46m) on the gap between testing on the host and the target Things…

This Youtube video by Controllers Tech shows how to use an STM32 to measure the frequency of an incoming rectangular wave using the input capture functionality of the timers. The code shown the video works but there are a few areas which could be improved, as I will now discuss. Then I make a performance improvement by using DMA instead of interrupts. The code is written using STM's HAL library which means that it does not have to handle the specific STM32's registers, which makes it more portable. However, HAL is still specific to the ARM and STM architecture, so you need to know what features are available in your internal peripherals to be able to write HAL function calls with the appropriate parameters. Initialising Global variables Controllers Tech declares a set of global variables at the top of main.c and initialises them…