I have several projects that use simple 328 based arduinos that I built myself, similar to the familiar "arduino on a breadboard" projects that I'm sure everybody has seen. They have just the bare minimum, no ftdi, etc.

Is it possible to drop in the 32U4 without modifying the circuits, or would I have to do a bunch of work to the circuits to get them to work with the 32U4 chips, and if so what are the general steps?


Just had a quick look at the datasheets, and the main difference I see physically is the 32u4 is 44 pin package and the 328 is either 32 or 28 pin. Also the 32U4 seems to have a lot more peripherals.

So based on that yes you will have to modify your circuit. Atmel are fairly consistant with ports and what their alternate functions are though.

eg SPI on portB, uart on portD

But you are just going to have to compare the pinouts on the datasheets see how they differ. And adjust pin connections accordingly.

Datasheets are easy to find. Good Luck!

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