16 LV Digital Inputs 8-Layer Stackable HAT for Raspberry Pi

The Raspberry Pi can read 26 input signals through the GPIO header, but some projects need to read more! Since all GPIO pins are wired directly to the local processor, some hardware is required to connect them to the real world.

The card has 16 optically isolated digital inputs. Each channel can accept inputs from 3V-24V. Inputs can read both DC and AC signals.

The card communicates with Raspberry Pi using only the I2C port, leaving all the other 24 GPIO pins available for your use. It has also an RS-485 header port, a power LED and a push-button that can be used to shut down the Raspberry Pi.

Pluggable connectors make the 1 Inputs card easy to use when multiple cards are stacked up.

An 8 inputs card is also available which offers higher voltages.

For any technical questions about this product please email support@sequentmicrosystems.com

Features

• Compatible with all 40-pin Raspberry Pi boards
• Sixteen LV (low-voltage) universal opto-isolated inputs 3V-24V
• Eight layers stackable to 128 inputs
• Pluggable Connectors 30-16 AWG wires
• Software self-test
  
• Command Line Driver
• Python Library
• Node-Red nodes

Compatibility

The card is compatible with all Raspberry Pi versions from Zero to the Pi 4. All stacked cards share the I2C bus using only two of the Raspberry Pi’s GPIO pins to manage all eight cards. This feature leaves the remaining 24 GPIOs available for the user.

Power Requirements

The card needs 5V to operate and can be powered from the Raspberry Pi or from its own 2-pin pluggable connector. The card draws 10mA. If power is applied to the 2-pin pluggable connector, no other power supply is needed for the Raspberry Pi.

Stacking Multiple Cards

Up to eight cards can be stacked on your Raspberry Pi. Each card is identified by jumpers you install to indicate the level in the stack. Cards can be installed in any order. A three-position jumper selects the stack level.

For your convenience, two jumpers are provided with each card.

Reverse Power Supply Protection

The board is protected against accidental reverse power supply with a 5.8A, 39 mOhm MOSFET which breaks the ground line if reverse power is applied.

Reset Pushbutton

Shutting down the Raspberry Pi by turning off the power can result in SD Card failure. To prevent this, a shutdown command needs to be used before power cut-off. But this requires a monitor, keyboard and mouse connected to the Pi.

A momentary push-button installed at the edge of the board provides a convenient way to shut down the Raspberry Pi. The button is routed to pin 37 (GPIO 26). You need to write a script that monitors this pin, and if pressed for more than the desired time, issues the shut-down command.

DIN-Rail Mounting

The card can be installed parallel on a DIN-Rail using the DIN-Rail Kit Type 1, or perpendicular using the DIN-Rail Kit Type 2.

Resources

• Main resource download page
  

Package Contents

• 1x 16-inputs card for Raspberry Pi
• 4x M2.5x18mm male-female brass standoffs
• 4x M2.5x5mm brass screws
• 4x M2.5 brass nuts
• 10x connector plugs
• 2x Pin jumpers

Software

Quick Start

• Plug your 16-INPUTS card on top of your Raspberry Pi and power up the system.
• Enable I2C communication on Raspberry Pi using raspi-config.
• Install the card software from github.com:
  ~$ git clone https://github.com/SequentMicrosystems/16inputs-rpi.git
  ~$ cd /home/pi/16inputs-rpi
  ~/16inputs-rpi$ sudo make install
  ~/16inputs-rpi$ 16inputs -h
• The program will respond with a list of available commands.

Software Interfaces

You can write your own application using the Command Line or Python Library provided. No programming is required if you use the Node-Red nodes we supply. You can drag and drop the functional blocks to design your application. Examples are provided at GitHub.

Self Test

The card can be tested before installation by running a simple command from the command line. The test LED located at the edge of the board will cycle on and off twice per second indicating that the card is operational.

RS485 Port

A standard RS485 transceiver permits the Raspberry Pi to communicate using any protocol including MODBUS, PROFIBUS, camera PTZ control, etc. The transceiver is connected to the serial port of the Raspberry Pi from the GPIO connector, pins 8 (GPIO14, TxD0) and 10 (GPIO15, RxD0). The Rx line is routed through a 2 pin jumper. The jumper needs to be installed in order to use the RS485 port. If the jumper is not installed, both pins can be used as GPIO's

Electrical Specifications

• Power Supply: 5V/8A pluggable connector with reverse polarity protection
• Onboard resettable fuse: 3A
• Opto-isolated Digital Inputs:
• Input Forward Current: Typical 5 mA, maximum 50 mA
• Low Voltage Input Series Resistor: 1.2K
• High Voltage Input Series Resistor: 10K
• Isolation Resistance: Minimum10¹² Ω

Revision History

As of 01/11/2022 we are now offering an updated version from Sequent which no longer offers jumper-selectable higher voltage input ranges (as well as some PCb layout changes)