Introduction to Arduino - Arduino Sketches: Tools and Techniques for Programming Wizardry - page 13

Arduino Mini
The Arduino Mini is a tiny device, useful for applications where space is reduced
to the absolute minimum (see Figure 1-7). It has 14 digital I/O pins and 4 analog
input pins. (Four more are available but are not broken out.) The device has the
strict minimum: it does not have a USB connector; it has no power regulator;
and it has no headers. Programming is done via an external USB or RS232 to
TTL serial adapter. It is shown in Figure 1-7.
Figure 1-7: The Arduino Mini
Arduino Micro
The Arduino Micro lives up to its name; it is one of the smallest Arduino boards
available. Despite its small size, it still has a large amount of input and output
pins; it has 20 digital input/output pins, of which 7 can be used as PWM outputs.
It also has 12 analog inputs.
The Micro is not designed to have shields but it does have an interesting layout,
as shown in Figure 1-8. It can be placed directly onto a breadboard.
Arduino Due
The Arduino Due differs from all other Arduino designs in that it is not
based on an AVR, but rather uses a microcontroller based on an ARM
Cortex-M3, the Atmel SAM3X8E. This advanced microcontroller is clocked