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.

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.

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.

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 Analog I/O (inputs and outputs), which may be configurable as digital inputs or pulse width modulation (PWM) outputs.