Are you interested in a small version of the Arduino Mega 2560?

Other Hardware Hardware Development
1

Hi everyone,

Once I started off with Arduino Pro Mini / Uno and build my first simple projects I integrated the different functionalities from those projects, e.g. sound module, display, XBee,..., I shortly reached the memory and pin boundaries. Yes you can say, program more efficient, so I did that and also looked the libraries to strip them from code I only needed. But at some point it came to an end.

I went for the Arduino Mega 2560. This is OK, but the size of the board bothered me. So I looked on the internet to get a small sized one but couldn't find anything that I could buy against a comparable price of the normal Mega 2560. So I decided to build one of my one. The road to there can be found at arduino.now4.nl. I've recorded all the steps I took to design and build the board, that I called the MegaMini, to share my experience.

The questions I have are:

  • Do you have any remarks on the board layout?
  • Should I've chosen a better list of available pins?
  • Is it already build by somebody else? Why not?

Looking forward for some feedback from you!

Arend

OSHPark MegaMini v2.jpg

Boards V2 Pro Mini.jpg

2

The problem with that is the fact that you are wasting a LOT of I/O. Did you break out SPI, I2C, and UART?
The design is great, though. A useful feature would be to have SMD pads on the back of the board for other pins, like the Teensy 3.1.

3

Thanks, yes, good idea to have SMD pads on the back to provide more IO. SPI, I2C and all 4 UART's are available.

4

Do you have a completed project with this?
BTW, how much did it cost to build?

Very nice design. You should check out CrossRoads' Bobuino Mini.

5

Hi,

We are making a similar project like yours. We are using the arduino mega 2560 schematic and we have a question about this part of the circuit:

Do yo know which it is the utility of this part?

Thanks :slight_smile: :slight_smile:

6

JoseMi:
Pasteboard - Uploaded Image

Do yo know which it is the utility of this part?

It looks like there are two independent parts to that portion of the circuit, tied together at the 5V supply symbol.

The left side looks like a switch that will connect the +5V and USBVCC nets together when VIN is less than 6.6V. It starts by taking VIN, and dividing it by two using a pair of resistors. That goes to the plus side of the voltage comparator, with 3.3V on the negative side. The output of the comparator (GATE_CMD) will be high if the CMP signal is above 3.3V (VIN is above 6.6V) and low if it is below 3.3V (VIN below 6.6V.) FETs are not my strong point, but I believe this FET will be ON when GATE_CMD is low, and OFF when it is high. Therefore, I believe that this will allow powering the board from the USB port when VIN is not connected, but when VIN is more than 6.6V, it will turn off the USB power connection and power the board strictly from VIN.

The other half of the circuit is the LP29085 - this is taking the 5V power (from whatever source) and regulating it down to 3.3V at 150 mA.

But please don't take my word for it, look up the parts and how they operate and confirm in on your own.

7

SS is correct AFAIK. It looks like the standard Arduino external power source selecting circuit.