Adafruit’s New “Grand Central” Board, a Return to the Arduino MEGA?

Alasdair Allan
2 min readAug 17, 2018

The Arduino classic form factor is dying. The Uno-like boards that became a de facto standard in the maker world are now quietly on the way out. While the ‘legacy’ Uno form factor is still around and viable, increasingly newer boards from Arduino use the MKR form factor, and the community has seemingly started to adopt Adafruit’s Feather form factor as the next de facto standard.

So with the size of new boards tending smaller, it’s interesting to see Adafruit resurrecting the Arduino MEGA form factor. To an old hand like me, it’s like seeing dinosaurs walking the Earth again. Of course, sometimes dinosaurs have their place.

The prototype PCB for the new Adafruit “Grand Central.” (📷: Adafruit)

Enter the new “Grand Central” Metro board, that’s only a working title by the way, which was just announced officially as upcoming by Limor Fried during yesterday’s Adafruit Live, “Ask an Engineer.”

Unlike the old Arduino MEGA board, which was built around the now ageing Microchip ATmega2560, the new Adafruit board is based around the SAM D51 processor, a 32-bit Arm Cortex-M4 running at up to 120 MHz.

Announcing the Metro “Grand Central” on Adafruit’s Ask an Engineer. (📷: Adafruit Industries)

Adafruit has made extensive use of Microchip’s SAM D21, which they used in their M0 boards for instance, but the SAM D21 didn’t come with enough pins for a MEGA. The SAM D51 comes in a 128-pin package, though, which is enough pins to build a MEGA-like board.

The announcement on Twitter of the upcoming “Grand Central.”

The new board will have, “all the Metro stuff you know and love,” along with MEGA-compatible GPIO, power, and a “flip up” SD card slot next to the processor.

According to Fried, the prototype was an “epic route” and the new board should be “really fast” running CircuitPython.

However it should also be useable with the Arduino development environment, and should “…run Arduino like a freight train.”

The board will also have 1MB of flash, and an “extra large” SPI Flash, perhaps around 16MB. There will also be a camera peripheral—with a 2×10 pin connector—that can be plugged directly into the end header block on the MEGA-like board.

While I’d argue that the next generation of microcontroller boards are going to be far more about the user experience than hardware, sometimes you just need a whole bunch of GPIO pins, and the new “Grand Central” will certainly provide that to those who need it.

The board is “coming soon” although this is only the first prototype, so people shouldn’t expect it to come out “…tomorrow, or next week. Give it a month or two, but it’s coming!”