Five ways, of course. In descending order.
5) Internal pullups. All the ATTiny and ATMega chips I’ve used have built-in pullups on all the input pins, which is REALLY CONVENIENT. Yes, if you’re a weekend warrior using a breadboard, you’ll just snap “stop being a b***h and add a resistor”. If you’re a pro making a production design, this resistor is another element you need to place on your board and add to your bill of materials, and it forces you to route your signal line near a supply line. This is highly relevant for some of the super-cramped wearable products I develop.
4) Generous I/O sink and source. This is probably my favorite feature of the low-end Atmel chips I use – they sink and source at least 30mA of current from every I/O pin. This is enough to directly drive a very bright LED, fan out a signal to a dozen old-school TTL devices, or fire a signal down a very long wire. Less sexy but more important, it gives you a lot more leeway before the output high voltage sags, which makes behavior more predictable.
3) Parts available in DIP package. I don’t want to reach for a breakout board and flux pen every time I make a new circuit. Don’t judge me.
2) Great toolchain. Avrdude, avr-gcc, et cetera, create a robust Bash-based cross-platform infrastructure. I don’t know what’s better – being able to code in the command line instead of the chipmaker’s system-grinding 500MB Eclipse fork, or being able to code at all on my Mac. Also, let’s be frank, C++ beats the hell out of Basic on syntax alone, and the libraries are garnish.
1) Arduino. The elephant in the microcontroller room, this is a deciding factor for a rapid prototyper. Say what you will about the Arduino IDE. Say what you will about the Arduino board. Say what you will about the Arduino culture. For free and zero registration, you get a fairly lightweight bootloader, well-written libraries that abstract out the obnoxious register math, and oodles of open-source code to
rip off use for inspiration. Plus, just add six holes (FTDI header) and your product has hackable Arduino street cred. Whammy.
Disclaimer for know-it-all dorks: I have not experimented with every Atmel chip in existence. For each of these loves, there is probably a chip that disproves the rule, or a competing chip that proves the rule. Yes, I think you’re very cool and your mother is very proud of you. My ATMega is still cooler than your PIC32SXF59ß∫®44SLC402EX900œß∂∆ç.