A couple of weeks ago when Jimmie Rodgers and Mitch Altman were in town at Hive13, the local hackerspace, I went to their soldering class. I was already past the level of soldering they taught (although not much! I’m still learning lots!) I went to the class to talk and to see how they did everything. While there I decided to buy the LoLshield + Diavolino kit that Jimmie was selling since he offered it for only $35. Considering a normal arduino is about $30 I hopped on this offer!
One of the main reasons that the Diavolino is so much cheaper than an Arduino is that the arduino has some extra circuitry such as a 5v regulator, FTDI usb-ttl chip for programming, and a couple other minor things. While I wish Jimmie would have bought the 5v regulator for an extra few bucks it’s not the end of the world. The Diavolino can still be powered by any power source from 4.5v to 5.5v. With the FTDI chip not included you need to buy one so the atmega microcontroller can actually be programmed. Most of the options I looked at were 5v FTD USB-TTL cables that several online electronics store offer and were generally $20 not including shipping. The cheapest one I could find was $18 from sparkfun. You could also go with a breakout board from sparkfun for only $15.
Before dedicating to one of these two I went to the arduino irc channel on freenode on irc and asked what other people would reccomend and someone mentioned the USB BUB board from modern devices. The nice thing about the USB BUB board is that it’s $14, and it comes with an extra 6 pin header input so you can rewire it for other boards that need FTDI chips to program them, but not in the same order as arduinos. Another nice thing is that there is a 3 pin jumper on it and depending on which two you connect it can supply either 5v or 3.3v logic. This is nice for some arduino clones and other avr/atmega devices that need 3.3v logic instead of the normal 5v logic for arduinos. If you are worried about the size of the BUB board then fear no more! The BUB board is very small. A lot smaller than I was expecting when I ordered it.
The BUB board comes without the jumper or headers soldered on, but to get all soldered together only takes about 5 minutes. Super simple!
Having this external programmer helps drop the price of the diavolino to about $15. That’s about half the price of a normal arduino. Of course the arduino has some nice extra features such as a built in regulator, FTDI chip, and a few other things, but the price make this a great deal! This is good if you want to have multiple arduinos since you only need one FTDI programmer for all of your boards, or if you are teaching a class and want to help lower costs.
I still have a few complaints about the Diavolino. It doesn’t have a voltage regulator, so unless you’re using a very stable and accurate power supply the Vcc on the the header pins tend to wander. I was trying to create a temp. logger as one of my first projects and found that due to this the temp, which was outputted as volts (every 10mV was 1 degree Kelvin) wandered about 10-20 mV, or 1-2°C. The battery pack is a bit annoying when you want to program it for a while, as it either has to be right next to the Diavolino or underneath of it even when not using it. I just took a two pin molex connector from a fan I took out of something a while ago and soldered it in between the Diavolino and battery holder as shown below. This way I can easily attach and detach it.
So while if you are only going to buy one I would definitely recommend an Arduino, if you need a cheap alternative for something like a class the Diavolino is great! Remember that the cost of development for the software, and the design are also in the cost of the Arduino so it’s always nice to support them!