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Some Musings about Embedded Application Development

Originally Published: 2015 July 12

With the ubiquity of ARM processors and *nix distributions running on them, embedded application development more closely resembles desktop or server application development. No longer is it mandated that an application be their own operating system. Anyone who has done application development in a *nix environment can develop for an embedded linux appliance. However, there are some significant differences that change the approach of development in these environments. Right after application design, hardware constraints dominate a developer's thoughts.

An embedded device would have a limited number of processes running at any one time and each must be a good team player. No single application can monopolize any resource on the device. Using a smart phone as an example, if you have an application take up all the memory or processing cycles, the other applications will cease to perform in a responsive manner. You may not even be able to make calls or text until a reboot clears the problem.

Memory is a major limitation. In a PC environment, one typically has ample memory. Even when this is not the case, you still have the option of upgrading the memory. While it may be possible to run a memory managed vm like Java on your device, your performance can vary greatly. Typically, the choice of languages for a new application will be closer to the metal (C or C++). This allows finer grained control over memory allocation. Embedded applications usually grab any memory it would need at startup. This prevents out of memory exceptions or application halts for garbage collection (if a managed environment is used). These types of errors can hide during development and QA but rear its ugly head in the field.

While SD cards are growing in capacity, the root disk space is still very limited. Often the SD card is not used, as EPROM may be preferred. Small, tight libraries are extremely important in this type of development. The ubiquity of BusyBox on embedded devices illustrates this. Even within the application code, keeping things small and simple is important. Many systems load the entire root filesystem into memory. Another side benefit of using small libraries is the inherent small memory footprint when the application is loaded.

This is by no means an all inclusive list. Hopefully it will assist any developers looking to make the leap to embedded development. As phones become more sophisticated and wearables become more common, now is a good time to look at embedded application development for fun and/or profit.

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