Select Between Multiple AVR Sketches with the Press of a Button

When you program an Arduino or other microcontroller board, you write the program, then upload the sketch. If new behavior is needed, you write a new program or modify it, then upload these new parameters. This works well, of course, but what if you need to change programs on a regular basis?

For that, the AVRMultiSketch by Jon Mackey may be just what you’re looking for. As described in the project’s readme file, “[It’s] an Objective-C OS X app that relinks and edits compiled sketch code (elf files) to allow multiple Arduino sketches to be loaded on and run from a single AVR MCU without modifying flash or the source code of the Arduino sketches in any way.”

So instead of reprogramming things over and over — or trying to cram the same functionality into one sketch with the potential hassle of deconflicting everything — you simply use this app to let them exist on the same AVR. A selector sketch is used on reset to choose the code to be run based on external (button) input, and a forwarder sketch sets everything up to run nicely.

An example board (and the inspiration for this project) that takes advantage of this functionality is shown at the end of the project’s GitHub listing. This performs a variety of programming tasks, and includes an SD card slot that enables it to load disk images. Selection is via the three buttons on top of the board. In theory, more I/O selections and sketch options could be used, but they would all need to fit in the MCU’s memory. Sketches are not loaded off of the SD card, lest there be any confusion.