This board needs FTDI cable to program it.

It is not Arduino compatible in the meaning of taking shields (just like every small form factor board isn't).

But it has all the same pins (exept 3.3V power and Vin*) available as female headers. The input and output pins that are right next to each other on original Arduino, almost are the same here, except digital 4 and 5. That means the order is:
RESET	0	1	2	3	4	VCC	GND	_	_	5	6	7	8
9	10	11	12	13	VCC	AREF	GND	A0	A1	A2	A3	A4	A5

It has power indication LED. Not an essential part, but it reminds you to remove the battery when not in use and I have also found it to be useful to notice shorts in my circuit – the power LED goes dim in that case.

It does not have 13th pin LED.

* - Mine has only 9V battery clip directly soldered to it, but this is the easiest part to modify. It also does not have ICSP header, but in the rare case a ISP programmer would be needed it is possible to access all these pins through female headers or remove the Atmega from socket.

So what's the purpose of such thing? I felt I needed a secondary controller besides my usual Arduino for testing things out. I missed that when programming my robot for a contest where IR transmitters were supposed to indicate important places and my attempt to make ATtinys do similar transmission failed. And now I have a task of learning about radio modules ahead of me and I want a familiar platform to test them out before trying to also mess with microcontrollers new to me that are supposed to go into the final product.

When considering the price remember these aspects:
  • Do you already have FTDI cable or for how much can you purchase it? (I managed to make one myself, but it takes precise etching and SMD soldering. Also the needed chip is not super cheap for experimentation. Further details http://www.instructables.com/id/FTDI-cable/ )
  • Do you have an Arduino (in working order) or AVR programmer to use for burning bootloader on a blank ATmega or can you get the controller with bootloader for reasonable price?

If all that described suits you and you feel ready to do some tightly packed soldering – it really wasn't too easy to get all wires to their right spot – then here is my documentation of the project.

Step 1: Gather stuff

Skills prerequisites:

Medium level of experience in soldering – this is really tight packed project and it's going to be really hard to fix cold or too messy joints in there.

Some understanding of electronics circuits and schematics preferred. You should be able to check the connections, firstly because it is really easy to make some mistakes in a circuit of this complexity level and secondly because I made the final drawing only after finishing my job and fixing couple of mistakes in it which means actually no one has yet made it „following the schematic“ and I might have passed a mistake in even though I did my best not to. Let me know if you find anything suspicious.

  • ATmega328 or 168. With bootloader (or a working Arduino or AVR programmer to use for burning it)
  • Stripboard – piece of 11 x 22 holes where strips run parallel to the shorter edge, but see note about the button type.
  • 7805 voltage regulator
  • 16MHz crystal oscillator
  • Pushbutton („mouse type“) – used as reset button, see images what the „mouse type“ means. You could use the regular round pushbutton in square housing, but it's footprint is wider and then you must make the stripboard wider by one or even two holes. Mouse button saves room here. If you have a broken mouse form recent decade, they actually can be found in there usually.
  • 28 pin socket for the ATmega
  • Female headers  - 2 x 14 or 14 + 8 + 4
  • Male headers – 6 pc. For FTDI cable connector.
  • 2 x 22pF capacitors (ceramic) – for the crystal
  • 4 x 10nF capacitors (ceramic)
  • 100nF capacitor (ceramic)
  • 100uF electrolytic capacitor (rated 16V or more)
  • 1 Kohm resistor – for reset pullup, 1/8 W is best size for my perfoboard  schematic.
  • ~330 ohm resistor – for the power indicator LED, can be other resistance value suitable for the LED, should be ¼ W, because there will be some power dissipation.
  • Rectifier diode – to protect against accidental reverse voltage. These can be found in all kinds of old power supplies – computer PSU, phone charger etc.
  • 9V battery clip – can be made form old 9V battery, but be careful while disassembling the metal outer part, I always manage to hurt myself in that process.
  • Wires – any insulated wire thin enough to fit through stripboard holes.

  • Paper and glue or sticker paper – for pin labels
  • Duct tape, double sided tape, cardboard – for protecting the bottom side

  • Soldering iron and all the rest usual tools needed for soldering job.
  • Some means to cut the stripboard in shape (tin shears for laminated board, a sharp knife and wooden block for breaking a plastic one)
  • Mini drill with some small grinder bit or other preferred means for cutting and removing traces on stripboard. On my drawing I marked entire surrounding of a hole to be removed, if you make just thin cuts, then in some places they should go in between holes instead of on the hole – especially I mean the male header pins area.

  • Multimeter for troubleshooting.
  • Components for testing some sketch (for blink sketch led and resistor for example).

  • FTDI cable. But if you are just going to order one and want to make this thing before it arrives you can actually test it out with help of an Arduino that has controller chip in a socket - check out further information in last steps.
<p>Much Thanks!!!...I'm doin' it!</p>
If you need even smaller - http://www.geocities.jp/Arduino_diecimila/obaka/project-2/index_en.html
really good and informative tutorial, i have one question in my mind, now, can i use all pins as if it is being used from Arduino board ? or any special care like adding cap or resisters or crystals etc to be added to use pins like input pin and output pin ?
If I understand your question correct then the answers is - the board can be used just the same as a factory made Arduino board, exept one thing. I have seen tutorials that allow you to connect a LED directly, without resistor, to pin 13. This is because a factory made Arduino has a built in LED there and they claim that it's current limiting resistor is for some reason in series with the pin header. My design does not have it. You may destroy your LED doing that. Here is a schematic for home-madeable board from official Arduino site<a href="http://http://arduino.cc/en/uploads/Main/ArduinoSeverinoSchematic.png" rel="nofollow"> http://arduino.cc/en/uploads/Main/ArduinoSeverinoSchematic.png</a> - this one actually has the resistor in parallel but there is no circuitry between the rest of the input/output pins and their pin headers.<br> <br> Slightly offtopic, there may arise some issues that your circuit components on pins 0 and 1 (TX and RX) may interfere while programming or with using serial connection commands, but this is exactly the same with factory made boards.
Thank you Sir, I was eagerly waiting for this answer and now can make board for my other projects also... <br> <br>Thanks again...
What an excellent Instructable. I'm definitely going to make one! <br>Just one small thing, in the materials list, I believe it should be 100uF electrolytic capacitor (rated 16v or more) not 100nF. <br>
Thank you very much. <br>Also thanks for reading with such attention. That clearly was a typo, fixed now.

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