Inputs (analog, digital, and interrupts) are indicated by the notation In.m, where n is the shield index (0, 1, or 2), and m is the input index, from the minimum to the maximum for that configuration. Interrupts are a special type of input used to start a software process based on a hardware trigger. For example, on the M-Duino 21+ shield, digital inputs range from I0.0 thru I0.12; however, only I0.5 and I0.6 may be configured as interrupts, and only I0.7 thru I0.12 may be configured as analog inputs.

Digital (and PWM) outputs are indicated by the notation Qn.m, where n is the shield index (0, 1, or 2), and m is the digital output index, from the minimum to the maximum. For example, on the M-Duino 21+ shield, the digital outputs range from Q0.0 thru Q0.7; digital outputs are configurable as pulse width modulation (PWM – which mimic analog outputs) on Q0.5 thru Q0.7 only.

Analog outputs are indicated by the notation An.m, again where n is the shield index (0, 1, or 2), and m is the analog output index, from the minimum to the maximum. For example, on the M-Duino 21+ shield, the analog outputs range from A0.5 to A0.7.

NOTE: The analog and PWM outputs share the same pins, and their behavior is selected by a switch setting, described in the User Guide.

These products offer Digital I/O (inputs and outputs), which may be configurable as analog or interrupt inputs, or pulse width modulation (PWM) outputs.