Creating a dev board for an ATmega microcontroller

Experimenting with tiny, surface-mount microcontrollers is a lot easier with a breakout board.

Not all chips are breadboard-friendly. Indeed, we’re seeing a trend towards an ever-higher percentage of ICs being available only in surface-mount packages. If you’re lucky, that might mean something relatively easy to hand solder, such as SOIC formats. But the various forms of quad flat package (QFP) can be difficult for the homelab bodger, like me.

Which was a problem when I decided I needed to use the ATmega4809 microntroller.

Sure, it’s available in a DIP-40 format, which uses the same die as the 48-pin TQFP version. But it sacrifices eight GPIO pins. Like phantom limbs, you can’t just ignore those missing pins. The datasheet advises: “the pins PB[5:0] and PC[7:6] must be disabled (INPUT_DISABLE) or enable pull-ups (PULLUPEN).”

I don’t know about you, but when I have a microcontroller I want access to all its capabilities. I selected the ATmega4809 precisely because of that high GPIO count. Besides, a 40-pin DIP chip is big.

The new dev board next to a 40-pin DIP chip for scale. The DIP chip is not the ATmega4809. My spare copies of that are evidently in a Very Safe Place and I couldn’t find them for this shot.

The immediate solution to this conundrum was to buy both DIP and TQFP versions, using the DIP chip on breadboard prototypes but with a view to targeting its physically smaller sibling in code.

But that’s still a compromise. I really wanted to be able to experiment with the fully fledged version of the ATmega4809. Which is why I came up with a dev board, which turns the TQFP version of the microcontroller into a 48-pin DIP.