Saturday, August 31, 2013

DIY Arduino Mega 2560

Here's the story: I was working on this frustrating Arduino project, and I decided to take a break. I went away to watch a little Star Trek and drink some water.
When I came back, my Arduino Mega was hot: really hot.
In this area:
The Arduino was not responding to the IDE. The only way I could program it was by using the USBtiny ISP.
That pretty much ruins the purpose of an arduino board, so I brought out the solder pot, desoldered the whole board, salvaging as many parts as I could.
Since the ATmega 2560 was not damaged, I decided to put it back to use:
The following is the process of how to

Make your own Arduino Mega

You think it's hard to solder SMD? Think again. This was my first time soldering SMD chips with 0.5mm pitch (in other words, REALLY SMALL).

Parts needed:

  • TQFP100, 0.5mm pitch to DIP adapter
  • Momentary push button
  • 6 headers (for ISP)
  • lots of wires
  • flux
  • Perf board
  • 16 MHZ crystal (if you salvaged chip from Arduino Mega)
  • OPTIONAL but recommended - double sided tape
  • OPTIONAL - 330 - 470 ohm resistors *2
  • OPTIONAL - 5 more headers for FTDI Serial communication
  • OPTIONAL - nuts and bolts

Step One

Stick one or two pieces of square double sided tape on the breakout board. This might help keep the chip in place when soldering it.

Step Two

Place the chip on! Please note the index corner on the chip to align it correctly. Make sure that the leads on the chip and the board line up REALLY well. The must be aligned.

Step Three

Time to start the soldering: apply WAY TOO MUCH flux (that means A LOT) onto the edges of the chip. You will need to use all of it, and maybe some more.
The secure the board:

Step Four

I do not have pictures for this. You will want to put a nice drop of solder on your iron and just drag it across the edges of the chip. Don't worry, it's all being soldered, even if you do not think it is.
You will probably have many solder bridges (especially on a chip this small).
Thats OK, just gently drag it off with the iron tip, use a solder sucker (be careful with it, you might bend the leads), or use even more flux to remove it. This step might be the most difficult

Step Five

Clean off the flux with water or alcohol:

Test the connections: any shorts? Something not connected?
Then you may proceed to cut and solder in some headers.

Then maybe you want to drill some holes in the four corners, if you want to.

Step Six

This step is mildly annoying. Print out the datasheet of the 2560 and start marking where

or any pins important to you, are
Mark it all!

This might help:

Step Seven

Start preparing your perf board. This step is very subjective to your needs and tastes. I like to have the TX and RX header so I can program this like a regular arduino.
I like to have a reset button
I like to have an LED on pin D13/ 27 of the chip
After all, it is a development board.

Start wiring the board!

Do some three dimensional wiring now.

Step Eight: last step

Time to test it....

The ISP programming worked!

Serial communication works.



Alright. It worked. Beautifully.
But I have something to admit. As I am typing this post, The finished board is hung up on my wall as a failure.


I can't use it as a regular Arduino Mega as I wished. Well, maybe I could have, but you will see why I couldn't.
The old Arduino Mega uses the FTDI UART, however the chip was the ATmega1280
I have a 2560, so I would need to go into some hassle to add a new board bootloader into Arduino IDE and all that trouble is just not worth it.

It definitely can be accomplished, however before I could do anything, the board burnt out.
I was in the middle of testing the serial communication: it worked perfectly. After five minutes, however, it started glitching. Then there were sparks... then smoke, then everything went south.
What happened?

When soldering in the oscillator crystal, make sure it DOES NOT SHORT THE LEADS. Note that it has a metal casing, so it should either be masked with electrical tape or place in another area.
Don't do this:
That ended up shorting XTAL 1 and 2, Vcc, and GND all together. The chip smoked and I wasted a lot of effort.

Lesson learned! *thats another nugget of information buddum crash*

As long as you follow all of these instructions, however, you will be able to accomplish what I would have if I have not made that mistake!

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