Home » Eight HV Digital Inputs 8-Layer Stackable HAT for Raspberry Pi
Eight HV Digital Inputs 8-layer stackable HAT for Raspberry Pi with opto-isolated inputs and RS485 port
Eight HV Digital Inputs 8-layer stackable HAT with opto-isolated inputs and RS485 port for Raspberry Pi.
Eight HV Digital Inputs 8-layer stackable HAT with opto-isolated connectors and DIP switch for Raspberry Pi integration
Eight HV Digital Inputs 8-layer stackable HAT with opto-isolated connectors for Raspberry Pi GPIO expansion
Stackable Eight HV Digital Inputs HAT for Raspberry Pi with eight opto-isolated inputs and DIP switch configuration
Eight HV Digital Inputs stackable HAT for Raspberry Pi with opto-isolated inputs and I2C interface
Eight HV Digital Inputs 8-layer stackable HAT for Raspberry Pi 360 view
Eight HV Digital Inputs 8-layer stackable HAT for Raspberry Pi with opto-isolated inputs and RS485 port
Eight HV Digital Inputs 8-layer stackable HAT with opto-isolated inputs and RS485 port for Raspberry Pi.
Eight HV Digital Inputs 8-layer stackable HAT with opto-isolated connectors and DIP switch for Raspberry Pi integration
Eight HV Digital Inputs 8-layer stackable HAT with opto-isolated connectors for Raspberry Pi GPIO expansion
Stackable Eight HV Digital Inputs HAT for Raspberry Pi with eight opto-isolated inputs and DIP switch configuration
Eight HV Digital Inputs stackable HAT for Raspberry Pi with opto-isolated inputs and I2C interface
Eight HV Digital Inputs 8-layer stackable HAT for Raspberry Pi 360 view
SKU: SM-I-011

Eight HV Digital Inputs 8-Layer Stackable HAT for Raspberry Pi

Eight opto-isolated inputs 3-32v or 32-240V, AC/DC with status LEDs; RS485/MODBUS; Works with Raspberry Pi ZERO to 5.

In stock
$45.00

Overview

Eight-layer stackable high-voltage digital input HAT for Raspberry Pi with 8 opto-isolated channels. Each channel provides separate connectors for low-voltage (3–32V) and high-voltage (32–240V AC/DC) signals. Software-selectable input mode supports wide-range (3–240V, 1 kHz) or high-speed (3–32V / 120–240V, 10 kHz) operation.

  • 8 opto-isolated digital inputs — each with separate low-voltage (3–32V) and high-voltage (32–240V AC/DC) connectors
  • Software-selectable wide mode (3–240V, 1 kHz) or high-speed mode (3–32V / 120–240V, 10 kHz)
  • Hardware watchdog and RS485/MODBUS for standalone or PLC integration
  • Eight-layer stackable — up to 64 inputs on one Raspberry Pi
  • High-isolation opto-couplers; uses only I2C — all GPIO pins remain free
  • Compatible with all Raspberry Pi versions from Zero to 5

Works with Open Automation Software

Compatible with widely used tools for control, monitoring, and system integration.

Command Line Python Node-RED CODESYS OpenPLC Home Assistant

INTERFACES AND I/O

I/O's Communication Software Integration
• 8 Opto-Isolated HV Digital Inputs (3–240V AC/DC) • I2C Port to Raspberry Pi • Command Line
• Separate LV (3–32V) and HV (32–240V AC/DC) connector per input • RS485/MODBUS Port (dual in/out connectors) • Python Library
• 8 Status LEDs (one per input) • Node-RED nodes
• Push Button (GPIO 26 / pin 37) • CODESYS Driver
• OpenPLC Module
• Home Assistant
Other Features
• Software-selectable 1 kHz (wide mode, 3–240V) or 10 kHz (high-speed mode) input sampling
• Hardware watchdog and resettable fuse (3A)
• 5V powered from Raspberry Pi or own pluggable connector
• Eight-layer stackable — up to 64 inputs per Raspberry Pi

DESCRIPTION

The Eight HV Digital Inputs HAT adds eight opto-isolated digital inputs to the Raspberry Pi, capable of detecting signals from 3V up to 240V AC or DC. Each channel provides a separate connector for low-voltage (3–32V) and high-voltage (32–240V) signals, making it safe and straightforward to connect different voltage levels on the same card.

HV Digital Inputs

Eight opto-isolated channels with separate LV (3–32V) and HV (32–240V AC/DC) connectors per input. Typical forward current 5 mA, maximum 50 mA. LV series resistor 2.2 KΩ; HV series resistor 120 KΩ. Isolation resistance minimum 1012 Ω.

Software Input Mode

Wide mode samples inputs from 3–240V at up to 1 kHz. High-speed mode supports 3–32V or 120–240V signals at up to 10 kHz. The mode is selected in software — no hardware changes or jumper moves required.

RS485/MODBUS

Dual RS485 connectors (in/out) allow daisy-chaining multiple devices on a single bus. When DIP switches are set to OFF, the card acts as a MODBUS RTU slave — any PLC, SCADA, or HMI can read all inputs without a Raspberry Pi. Set to ON for Pi passive bridge mode.

Hardware Watchdog

The onboard watchdog monitors the Raspberry Pi and power-cycles it if a reset command is not received within the configured timeout. Disabled at power-up; activated automatically after the first reset command is issued by the application.

Stacking

Up to 8 Eight HV Digital Inputs HATs stack on one Raspberry Pi for 64 opto-isolated inputs. Three DIP switch positions (ID0, ID1, ID2) select the stack level. Cards of different Sequent HAT types can be freely mixed. Only I2C is used — all 24 GPIO pins remain free.

TECHNICAL DETAILS

CARD LAYOUT

Eight HV Digital Inputs HAT for Raspberry Pi — card layout

MECHANICAL SPECIFICATIONS

Eight HV Digital Inputs HAT Mechanical Specifications

DIP SWITCH AND STACKING

The onboard 6-position DIP switch configures the stack address and RS485 port behavior. Up to eight Eight HV Digital Inputs HATs can be stacked on one Raspberry Pi; cards can be stacked in any order.

Eight HV Digital Inputs HAT DIP Switch

Switch Name Function
TERM RS485 termination ON = enables 120 Ω termination resistor; set ON if this card is the last on the RS485 bus
ID0 Stack ID bit 0 Binary stack address bit 0 (LSB) — sets card level 0–7
ID1 Stack ID bit 1 Binary stack address bit 1
ID2 Stack ID bit 2 Binary stack address bit 2 (MSB)

ELECTRICAL SPECIFICATIONS

Power
Power supply 5V/8A pluggable connector with reverse polarity protection
Power consumption 10 mA
Onboard resettable fuse 3 A
Opto-Isolated Inputs
Forward current Typ. 5 mA / Max. 50 mA
LV series resistor 2.2 KΩ
HV series resistor 120 KΩ
Isolation resistance Min. 1012 Ω

POWER REQUIREMENTS

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

COMMUNICATION INTERFACES

RS485 / MODBUS

The Eight HV Digital Inputs HAT includes a standard RS-485 transceiver with dual connectors (in and out) for easy daisy-chaining. The port can be accessed by the onboard processor or by the Raspberry Pi. The operating mode is configured using the DIP switch.

When the TX and RX DIP switches are set to ON, the Raspberry Pi communicates directly with any device that has an RS-485 interface. In this mode the card functions as a passive bridge. To use this configuration, the onboard processor must first release control of the RS-485 bus:

~$ 8inputs [0] rs485wr 0 0 0 0 0

When the DIP switches are set to OFF, the card operates as a MODBUS RTU slave. Any MODBUS master — PLC, SCADA, or HMI — can read all inputs using standard MODBUS commands, with no Raspberry Pi required. A full list of supported MODBUS registers is available on GitHub.

The TERM position on the DIP switch enables the RS485 line terminator. Set it to ON if the card is last on the RS485 chain.

HARDWARE WATCHDOG

The onboard hardware watchdog monitors the Raspberry Pi. If the application fails to send a reset command within the configured timeout, the watchdog cuts power to the Pi and restores it after the configured off period. The watchdog is disabled at power-up and is activated automatically after the first reset command is received. Use 8inputs -h to see all watchdog commands.

Parameter Value
Initial timeout period Configurable — allows time for Raspberry Pi to boot and start the application
Running timeout period Configurable — normal operating timeout
Off period Configurable — duration the Raspberry Pi power is cut when timeout triggers
Reset counter Stored in non-volatile flash; can be read or cleared at any time

COMPATIBILITY

Interface I2C
GPIO used GPIO2 (SDA), GPIO3 (SCL) — 2 pins only; remaining 24 GPIO pins stay free
Max stack 8 cards of each type; different Sequent HATs can be freely mixed
Compatible with All Raspberry Pi versions from Zero to 5 (40-pin GPIO header)

DOWNLOADS

User's Guide (PDF) Schematics (PDF) CAD Software & Integrations
User's Guide V1.0 Schematic V1.0 2D CAD Drawing Command Line
Schematic V2.0 3D STEP Model Python Library
3D Printing Enclosure Node-RED nodes
CODESYS Driver
OpenPLC Module
Home Assistant

COMPLIANCE

RoHS and REACH Compliance Declaration

WHAT'S INCLUDED

When you purchase the card you will receive the following items:

1. Eight HV Digital Inputs HAT for Raspberry Pi
Eight HV Digital Inputs HAT for Raspberry Pi
2. Mounting Hardware
Mounting hardware for Eight HV Digital Inputs HAT
  • Four M2.5×18mm male-female brass standoffs
  • Four M2.5×5mm brass screws
  • Four M2.5 brass nuts
3. Connector Plugs for all Inputs and Outputs
Connector plugs for Eight HV Digital Inputs HAT
  • All required mating connector plugs for field wiring

QUICK START

  1. Plug your card on top of your Raspberry Pi and power up the system.
  2. Enable I2C communication on Raspberry Pi using raspi-config.
  3. Install the software from GitHub:
    ~$ git clone https://github.com/SequentMicrosystems/8inputs-rpi.git
    ~$ cd 8inputs-rpi
    ~/8inputs-rpi$ sudo make install
    ~/8inputs-rpi$ 8inputs -h

The program will respond with a list of available commands. To read more about the CLI, please refer to the README file. If you would rather use a different platform, you can access the same functionality through dedicated, ready-to-use integrations in the Downloads tab above.

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