Compact mega2560 boards?

The larger SRAM on the Mega2560 makes it easier for my projects, but the physical size is a problem.

I see various small form factor boards on Aliexpress and Ebay. They are about half the size of a conventional Mega2560 board, but appear to have the same number of pins. Some have a USB interface, some don’t.

Has anyone tried any of these, and are they functional/reliable?

Robotdyn has small Mega Arduinos with and without USB chip
https://robotdyn.com/catalogsearch/result/?q=mega
scroll the page down to Mega Minis
I have other Robotdyn products and they are good quality

Juraj:
Robotdyn has small Mega Arduinos with and without USB chip
https://robotdyn.com/catalogsearch/result/?q=mega
scroll the page down to Mega Minis
I have other Robotdyn products and they are good quality

Thye do look interesting, but it appears that they are running the 3.3V version at 16Mhz, which I thought was out of spec for a ATmega.

srnet:
Thye do look interesting, but it appears that they are running the 3.3V version at 16Mhz, which I thought was out of spec for a ATmega.

The ATMega2560 is only specced to run on 4.5-5.5V. The ATMega2560V is specced to run at lower voltage, but not at 16MHz.

They are also available on ebay and similar places, including versions with a CH340G USB interface.

BJHenry:
The ATMega2560 is only specced to run on 4.5-5.5V. The ATMega2560V is specced to run at lower voltage, but not at 16MHz.

Thats what I thought.

You do question why they appear to be selling out of specification products, I wonder if the average customer realises.

Chat history from website robotdyn.com on June 12, 2019

16:42 You: how do you run ATmega 2560 16 MHz at 3.3 V on Mega 2560 PRO MINI? 3.3 V is out of specs for 2560 at 16MHz

14:33 Sales Dept., manager: Hello,

This is achieved by bypassing the integrated voltage regulator

I don't understand it. Do you? Should I ask something else?

There is also the Mega 2560 R3 Core Für Arduino Kompatibel Mini 2560.
They sell a small sized Due board too.

srnet:
Thye do look interesting, but it appears that they are running the 3.3V version at 16Mhz, which I thought was out of spec for a ATmega.

That’s a translation issue. There is no 3v3 powered processor but a 3v3 regulator in addition to the 5v regulator, just like a full sized Mega.

WattsThat:
That’s a translation issue. There is no 3v3 powered processor but a 3v3 regulator in addition to the 5v regulator, just like a full sized Mega.

From the description of one of the 2560 boards;

"In addition, you can create a project with 3.3V or 5V logic level. Onboard has a solution for switch between 3.3V or 5V."

And there is a jumper on the schematic that selects VCC on the processor between 3.3V and 5V ...........