Industrial Automation 8-Layer Stackable HAT for Raspberry Pi
Four Digital Inputs, four 0-10V Inputs and Outputs, four 4-20mA Inputs and Outputs, four 4A/24V Outputs, 1-Wire, RS485, Watchdog, RTC.
Overview
Industrial automation hardware for Raspberry Pi with modular I/O, standard communication interfaces, and support for widely used control and monitoring systems. The Industrial Automation HAT combines digital inputs, voltage and current analog I/O, MOSFET outputs, RS485/MODBUS, and 1-Wire interfaces in a compact, stackable platform for control, monitoring, and data acquisition.
- Digital, voltage, and current I/O on one board
- Native RS485 / MODBUS and 1-Wire interfaces
- Four MOSFET outputs for direct load control
- Up to 8 cards of each type can be stacked and mixed with other Sequent HATs for virtually unlimited I/O expansion
- Designed for control, monitoring, and data acquisition systems
- CE Certified to comply with EU regulatory requirements
Works with Open Automation Software
Compatible with widely used tools for control, monitoring, and system integration.
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INTERFACES AND I/O
| I/O's | Communication | Software Integration |
|---|---|---|
| • Four Optically Isolated Digital Inputs | • I2C Port to Raspberry Pi | • Command Line |
| • Four 0-10V or ±10V 16 bit Analog Inputs | • RS485/MODBUS Port | • Python Library |
| • Four Optically Isolated 4-20mA Inputs | • 1-Wire Interface | • Node-RED nodes |
| • Four 0-10V 14 bit Analog Outputs | • CODESYS Driver | |
| • Four 4-20mA 14 bit Analog Outputs | • OpenPLC Module | |
| • Four General Purpose LED Outputs | • Home Assistant | |
| • Arduino | ||
| Other Features | ||
| • Software controlled switches for analog input range selection | ||
| • Wide range 12-24V power supply delivers 5V/5A to Raspberry Pi | ||
| • 215Hz sample rate on 0-10V inputs, 675Hz sample rate on 4-20mA inputs | ||
| • Load interruption detection on 4-20mA outputs | • Pluggable Connectors 26-16 AWG wires | |
| • TVS Protection on all Inputs | • On Board Hardware Watchdog and fuse | |
| • Real Time Clock With CR2032 Battery Backup | • Eight Level Stackable | |
DESCRIPTION
The Industrial Automation HAT provides everything needed to build sophisticated industrial control, monitoring, and data acquisition systems with Raspberry Pi.
Four optically isolated 4-20mA inputs read sensors from 2-wire, 3-wire, or 4-wire transmitters.
Four 4-20mA outputs control actuators with 14-bit resolution and automatic load interruption detection.
Four 16-bit 0-10V or ±10V analog inputs read high-precision voltage signals. The input range is software-selectable per channel — no jumpers or DIP switches required.
Four 14-bit PWM 0-10V outputs control proportional actuators and drives.
Four open-drain MOSFET outputs switch DC loads up to 4A at 24V for direct control of solenoid valves, relays, and motors.
Four optically isolated digital inputs accept signals from 0 to 24V. Four programmable LED outputs display the state of any digital or analog channel.
The Real-Time Clock with CR2032 battery backup keeps accurate time through power failures, making the card ideal for data logging and time-stamped event recording.
The hardware watchdog automatically power-cycles the Raspberry Pi if the software becomes unresponsive, ensuring continuous operation in unattended deployments.
TVS diodes on all inputs protect against ESD and transient spikes. An onboard resettable fuse protects against accidental shorts.
TECHNICAL DETAILS
CARD LAYOUT
MECHANICAL SPECIFICATIONS
DIP SWITCH AND STACKING
The onboard six-position DIP switch configures both the stack address and the RS485 port behavior. Cards of different Sequent HAT types can be freely mixed in the same stack.
| Switch | Name | Function |
|---|---|---|
| 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) |
| RX | RS485 RX select | ON: Raspberry Pi receives RS485 directly |
| TX | RS485 TX select | ON: Raspberry Pi drives RS485 directly |
| TERM | RS485 termination | Enable on the last card in an RS485 chain to prevent signal reflections |
ELECTRICAL SPECIFICATIONS
| Power | |
|---|---|
| Power supply | 3.5mm Pluggable Connector, 12–24 VDC / 1A |
| Power consumption | 50 mA @ 24 V |
| Onboard resettable fuse | 2.5 A |
| 0–10 V Inputs | |
|---|---|
| Maximum Input Voltage | 12 V |
| Input Impedance | 20 KΩ |
| Resolution | 16 bits |
| Sample rate | 215 Hz |
| Full scale linearity | 0.15% |
| 0–10 V Outputs | |
|---|---|
| Minimum Output Load | 1 KΩ |
| Resolution | 14 bits |
| Full scale linearity | 0.1% |
| 4–20 mA Inputs | |
|---|---|
| Sample rate | 675 Hz |
| Input impedance | 150 Ω |
| Resolution | 12 bits |
| 4–20 mA Outputs | |
|---|---|
| Resistive load | Max 1 KΩ @ 24 V external |
| Maximum external voltage | 24 V |
| Resolution | 14 bits |
| Open Drain Outputs | |
|---|---|
| Maximum Output Current | 4 A |
| Maximum Output Voltage | 24 V |
POWER REQUIREMENTS
Power supply: The card requires an external 12–24VDC power supply connected to its own pluggable power connector. The card supplies 5V and up to 4A continuous, 5A peak to the Raspberry Pi over the GPIO bus, eliminating the need for a separate Raspberry Pi power supply. Operating current is 50mA at 24V.
PLUGGABLE CONNECTORS
All I/Os connect to heavy-duty 3.5mm pitch pluggable screw terminal connectors rated at 8A, accepting wire gauges from 26 to 16 AWG. Connectors can be unplugged from the board for convenient field wiring and debugging without disturbing the rest of the installation.
4-20mA CURRENT LOOPS
Since 4-20mA current loops are optically isolated from the system ground, they can be used with isolated or non-isolated, 2, 3 or 4 wire transmitters. In all cases an external power supply must be provided (up to 24VDC).
In the following diagrams the following notation is used:
| 1 | External 4-20mA Transmitter |
| 2 | Industrial Automation Card |
| 3 | External Power Supply |
| 4 | External 4-20mA Receiver |
4-20mA INPUT LOOPS
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| Case 1: Two wire transmitter, shared ground. | Case 2: Three wire transmitter, shared ground. | Case 3: Four wire transmitter, isolated ground. |
4-20mA OUTPUT LOOPS
The 4-20mA outputs are driven by Open Drain MOSFETS with a common ground. Connect your 4-20mA receiver as shown in the following diagram:
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| 4-20mA Output — Open Drain MOSFET with common ground |
FIELD CALIBRATION
All analog inputs and outputs are factory-calibrated.
However, firmware commands allow the user to recalibrate the board or perform higher-precision calibration if required.
Calibration is performed using a two-point method. The selected calibration points should be placed as close as possible to the minimum and maximum values of the measurement range.
Input Calibration
To calibrate the inputs, the user must apply known analog reference signals. For example, calibrating 4–20 mA inputs requires providing accurate 4 mA and 20 mA current sources.
Output Calibration
To calibrate the outputs, the user must:
- Issue a command to set the output to a desired value.
- Measure the actual output using a calibrated instrument.
- Issue the corresponding calibration command to store the measured value.
Storage and Reset
Calibration values are stored in non-volatile flash memory, and the input transfer curve is assumed to be linear.
If an incorrect command or value is entered during calibration, a RESET command can restore all channels in the selected group to their factory calibration values. After a reset, the calibration procedure can be repeated.
Calibration Without External Sources
The board can also be calibrated without external analog signal sources by:
- Calibrating the outputs first, and
- Routing the calibrated outputs to the corresponding input channels for input calibration.
The following firmware commands are available for performing calibration:
CALIBRATE 0-10V INPUTS: megaind <id> uincal <channel> <value>
RESET CALIBRATION OF 0-10V INPUTS: megaind <id> uincalrst <channel>
CALIBRATE 4-20mA INPUTS: megaind <id> iincal <channel> <value>
RESET CALIBRATION OF 4-20mA INPUTS: megaind <id> iincalrst <channel>
CALIBRATE 0-10V OUTPUTS: megaind <id> uoutcal <channel> <value>
RESET CALIBRATION OF 0-10V OUTPUTS: megaind <id> uoutcalrst <channel>
CALIBRATE 4-20mA OUTPUTS: megaind <id> ioutcal <channel> <value>
RESET CALIBRATION OF 4-20mA OUTPUTS: megaind <id> ioutcalrst <channel>COMMUNICATION INTERFACES
HARDWARE WATCHDOG
The Industrial Automation HAT includes a hardware watchdog that ensures your system automatically recovers if the Raspberry Pi software becomes unresponsive. The watchdog is disabled at power-up and activates after it receives the first reset command from the Raspberry Pi.
| Watchdog Parameters | |
|---|---|
| Default timeout | 120 seconds |
| Power-off duration on trigger | 10 seconds |
| Initial timeout period | Configurable — allows time for Raspberry Pi to boot and start the application |
| Running timeout period | Configurable — normal operating timeout |
| Reset counter | Stored in non-volatile flash; can be read or cleared at any time |
For a full list of watchdog commands, run: megaind -h
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 with virtually no upper limit on total I/O |
| Compatible with | All Raspberry Pi versions from Zero to 5 (40-pin GPIO header) |
FIRMWARE UPDATE
The onboard microcontroller firmware can be updated in the field. The update tool downloads the latest firmware from Sequent Microsystems' servers and flashes it to the board over I2C.
Running the Update
~$ cd ~/megaind-rpi/update/
~/megaind-rpi/update$ ./update <id>
Replace <id> with the board stack address (0-7). Full instructions including recovery procedures are available at:
https://github.com/SequentMicrosystems/megaind-rpi/tree/master/update/README.md
DOWNLOADS
| User’s Guide (PDF) | Schematics (PDF) | CAD | Software & Integrations |
|---|---|---|---|
| User’s Guide V2.0 | Schematic V2.0 | 3D STEP File V3.2 | Command Line |
| User’s Guide V3.0 | Schematic V3.0 | 2D CAD Drawing | Python Library |
| User’s Guide V3.2 | Schematic V4.0 | Node-RED nodes | |
| User’s Guide V4.0 | Schematic V5.0 | MODBUS interface | |
| User’s Guide V5.0 | CODESYS Library | ||
| OpenPLC Example | |||
| Home Assistant |
COMPLIANCE
RoHS and REACH Compliance Declaration
WHAT'S INCLUDED
When you purchase the card you will receive the following items:
| 1. Industrial Automation Card for Raspberry Pi |
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| 2. Mounting Hardware | |
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| 3. Connector Plugs for all Inputs and Outputs | |
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QUICK START
- Plug your card on top of your Raspberry Pi and power up the system.
- Enable I2C communication on Raspberry Pi using
raspi-config. - Install the software from GitHub:
~$ git clone https://github.com/SequentMicrosystems/megaind-rpi.git~$ cd /home/pi/megaind-rpi~/megaind-rpi$ sudo make install~/megaind-rpi$ megaind
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" Section
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