Digital Input

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The Digital Input block reads the state of digital input pins from any available GPIO port on Microchip microcontrollers. The block supports configurable electrical characteristics including pull-up and pull-down resistors, and provides flexible output formats for easy integration into Simulink models. Key Features: - [Pin Mapping and PPS Guide] - Microchip Device Datasheet - GPIO/PORT section

Overview

The Digital Input block reads the state of digital input pins from any available GPIO port on Microchip microcontrollers. Selected pins are configured as digital inputs with user-selectable pull-up, pull-down, or hi-impedance modes. When the block output is defined as one uint16, users should only use bits corresponding to the selected pins.

When to use:

Reading button/switch states
Monitoring external digital signals
Interfacing with digital sensors
Reading encoder signals

When NOT to use:

For pins that require analog input (use ADC block instead)
For pins configured as outputs elsewhere in the model

Block Dialog

Ports

Output

Port	Data Type	Description
Port signal	boolean or uint16	Digital state of selected pin(s). If multiple pins are selected without PACK option, each pin has its own boolean output. If PACK option is enabled, a single uint16 output contains pin states in corresponding bit positions.

Parameters

Parameter	Variable	Type	Description
Port	`PORT`	popup	GPIO port selection (A, B, C, etc.). Dynamically populated based on target device pin map. Shows available pin indices for each port.
Pins	`PIN`	edit	Array of pin indices to read, e.g., `[0]` or `[0 1 2]`. Valid range is `[0..15]` for 16-bit ports or `[0..31]` for 32-bit ports. Out-of-range or unavailable pins are automatically filtered out with a warning.
Input mode	`INPUT_PIN_MODE`	popup	Chip-dependent. Electrical configuration: `Hi-impedance (default)`, `Pull-up`, or `Pull-down`. Only visible on newer dsPIC and PIC32 chips (Arch 1,2,3,4,8 with CN.type==2). Hidden on older dsPIC and all SAM devices.
set block output as one uint16/uint32	`PACK`	checkbox	Conditional. When enabled, all selected pins are packed into a single uint16 (16-bit ports) or uint32 (32-bit ports) output with bits corresponding to pin numbers. When disabled, each pin has an individual boolean output. Always visible.
Request exact simultaneous sampling	`SIMULTANEOUS`	checkbox	Conditional. When enabled, all pins are read in a single PORT register access for atomic simultaneous sampling. Only visible when multiple pins are selected AND PACK is disabled.
Block execution ordering	`ORDERING`	popup	Controls block scheduling: `None`, `Input`, `Output`, or `Input & Output`.
Sample Time	`SampleTime`	edit	Sampling interval in seconds. Use `-1` for inherited sample time.

Device Support

Input Mode Parameter Visibility:

Visible: dsPIC30F, dsPIC33F, dsPIC33E, dsPIC33C, dsPIC33A, PIC32, PIC32A (Arch 1,2,3,4,8 with CN.type==2)
Hidden: Older dsPIC chips with CN.type≠2, all SAM (SAME70/SAMS70/SAMV71/SAMx2/SAMx5) devices
- When hidden, pins default to Hi-impedance mode

Output Data Type:

16-bit ports (dsPIC): PACK mode outputs uint16, unpacked mode outputs individual boolean per pin
32-bit ports (SAM/PIC32A): PACK mode outputs uint32, unpacked mode outputs individual boolean per pin

Port Availability:

The Port popup is dynamically populated from the chip pin map at model initialization
Only ports with at least one available digital pin are shown
Pin indices shown in brackets reflect actual chip capabilities (e.g., A [0:15] or B [0 2 4 8])

Examples

Programmatic Setup

% Add block to model
add_block('MCHP_Blockset/Digital IO/Digital Input', [mdl '/DigitalIn']);

% Configure key parameters
set_param([mdl '/DigitalIn'], 'PORT', 'A');
set_param([mdl '/DigitalIn'], 'PIN', '[0 1 2]');
set_param([mdl '/DigitalIn'], 'INPUT_PIN_MODE', 'Pull-up');

Troubleshooting

Problem: Block output always reads 0 or 1 regardless of input

Solution: Check that the pin is not configured as an output elsewhere in the model. Verify ANSEL configuration if the pin has analog capability.

Problem: Floating input causes unstable readings

Solution: Enable pull-up or pull-down resistor in the Input mode parameter, or add external resistors to your circuit.

Problem: Multiple pins don’t update simultaneously

Solution: All pins on the same port are read atomically from the PORT register in a single instruction. If pins are on different ports, they will be read sequentially.

Digital Output — Write to digital output pins
Digital Output Write — Direct output write block
Digital Output Read — Read output latch state