Industrial Automation 8-Layer Stackable HAT for Raspberry Pi

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. 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 Open Drain PWM Outputs • Home Assistant • Four General Purpose LED Outputs • 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. 4–20 mA Inputs Four optically isolated 4-20mA inputs read sensors from 2-wire, 3-wire, or 4-wire transmitters. 4–20 mA Outputs Four 4-20mA outputs control actuators with 14-bit resolution and automatic load interruption detection. 0–10 V Analog Inputs 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. 0–10 V Analog Outputs Four 14-bit PWM 0-10V outputs control proportional actuators and drives. MOSFET Outputs Four open-drain MOSFET outputs switch DC loads up to 4A at 24V for direct control of solenoid valves, relays, and motors. Digital Inputs & LED Outputs Four optically isolated digital inputs accept signals from 0 to 24V. Four programmable LED outputs display the state of any digital or analog channel. Real-Time Clock 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. Hardware Watchdog The hardware watchdog automatically power-cycles the Raspberry Pi if the software becomes unresponsive, ensuring continuous operation in unattended deployments. Protection 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 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: 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 RS485 / MODBUS The Industrial Automation HAT includes a standard RS-485 transceiver that can be accessed either by the onboard processor or by the Raspberry Pi. The operating mode is configured using the TX and RX switches on the SW1 DIP switch. When TX and RX 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, implementing only the hardware signal levels required by the RS-485 protocol. To use this configuration, the onboard processor must first release control of the RS-485 bus: ~$ megaind 0 rs485wr 0 0 0 0 0 When TX and RX are set to OFF, the card operates as a MODBUS RTU slave. Any MODBUS master — PLC, SCADA, or HMI — can read all inputs and control all outputs using standard MODBUS commands, with no Raspberry Pi required. A full list of supported MODBUS registers is available on GitHub. In both modes, the onboard processor must be configured to either release or control the RS-485 signals accordingly. Refer to the command-line help for further details. 1-Wire Interface The Industrial Automation HAT includes a standard 1-Wire bus for connecting digital temperature sensors. Up to 16 DS18B20 sensors can be connected in parallel on a single two-wire cable, covering large areas such as multi-zone HVAC systems or distributed monitoring installations. Sensors are accessible from the command line, Python scripts, Node-RED, and the MODBUS interface, making integration straightforward regardless of your software environment. 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. WARNING: Stop all processes that access the card (Node-RED flows, Python scripts, cron jobs) before starting a firmware update. Accessing the card during an update may corrupt the firmware. 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 CE EMC Test Report CE Certification WHAT'S INCLUDED When you purchase the card you will receive the following items: 1. Industrial Automation Card for Raspberry Pi 2. Mounting Hardware Four M2.5×19mm male-female brass standoffs Four M2.5×5mm brass screws Four M2.5 brass nuts 3. Connector Plugs for all Inputs and Outputs Six 8-pin female mating connector plugs for I/Os One 5-pin female mating connector plug for RS485 and 1-Wire ports One 2-pin female mating connector plug for power 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