One of the distinguishing characteristics of beginner-friendly microcontroller platforms– Arduino, PICAXE, and a few dozen others– is that they neatly wrap up and hide the nuts-and-bolts details of interfacing with the hardware.

Like everything else, it’s a blessing and a curse. The benefits are clear: A new user who has just acquired an Arduino can plug it in, blink an LED, and have a working demonstration of two-way serial communication in just a few minutes.

The drawbacks are a little harder to see. When you just use one line of initialization that calls a “library,” it’s easy to overlook exactly what’s involved: how many lines of code have invisibly been added to your program? What memory structures have been allocated? What interrupts are now going to disrupt program flow and timing? There’s also a portability issue. We often hear from people who got started with Arduino but now want to explore other AVR microcontroller systems, and don’t know how or where to start the migration process.

In what follows we discuss a minimal setup for serial communication with AVR microcontrollers, and give two example implementations, on an ATmega168 and on an ATtiny2313. While this fundamental “AVR 101” stuff, we’re approaching the problem (this time) from the migration standpoint. Suppose that you had an Arduino based project, where you relied on serial communication– using the library functions–between that hardware and your computer. From there, how would you migrate to a stand-alone AVR microcontroller with similar functionality, or even to a different microcontroller?
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