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Stackable Raspberry Pi home automation “X-HAT” aims for maximum I/O

Sep 11, 2017 — by Eric Brown 11,590 views

On Kickstarter: a stackable “Raspberry Pi Mega-IO Expansion Card” for home automation offers a 12-bit DAC, 8x ADC, 8x relays, 8x opto-inputs, and 6x GPIO.

A startup by Mihai Beffa called Sequent Microsystems has launched a Kickstarter campaign for a Raspberry Pi add-on card that is loaded with inputs, outputs, and relays designed for home automation. The stackable Raspberry Pi Mega-IO Expansion Card is an attempt to “integrate as many Home Automation functions as possible into a Raspberry Pi platform,” says the KS page.

Raspberry Pi Mega-IO Expansion Card on its own with Raspberry Pi (left) and in the maximum quad-stack configuration
(click images to enlarge)

A single Mega-IO Expansion Card combined with a Raspberry Pi 3 SBC can simultaneously control HVAC, security, irrigation, and soil humidity detection I/O. This would otherwise require multiple I/O, relay, and ADC cards, and a tangle of cables in between, says Beffa.

The Mega-IO board sells for $25, $29, or $34 individually, depending on how quickly you join the campaign, and $96 for a four-pack. At publication time, the project was a third of the way toward its $10K goal. The boards are expected to ship in Mar. 2018.

Mega-IO top detail view (left) and block diagram
(click images to enlarge)

Specifications listed for the Raspberry Pi Mega-IO Expansion Card include:


  • 8x relays (10A/250V)
  • 8-channel 12-bit ADC
  • 12-bit DAC
  • 8-channel optically isolated inputs
  • 4x 16V/140mA open collector outputs
  • 6x GPIOs
  • 23x free GPIOs carried through from Raspberry Pi

The Mega-IO can be stacked up to four cards high. This would provide a complete system with up to 95x GPIOs, 32x relays, 32x opto-isolated inputs, and 4x DAC outputs.

The interfaces are controlled via an ST STM8L151C8U6, an 8-bit, 16MHz MCU with 64KB flash. The board itself follows HAT specifications in every way except for size, which replicates the horizontal dimensions of the Raspberry Pi itself. Sequent Microsystems refers to it as an X-HAT (eXpanded HAT).

Mega-IO 3-stack configuration with cabling (left) and sample Node RED code for monitoring opto-isolated inputs
(click images to enlarge)

All thru-hole components are mounted on top, and all surface mounts are on the bottom. A two-position jumper selects the stack order of the card, and each relay has its own 5-pin terminal block. There’s also a power connector that can provide 5V external power.

A command line utility is available for download, and a Raspbian image with the Node RED visual programming tool will soon be available. The image will include Mega I/O specific Node RED examples including setting the D/A output, testing A/D input, reading opto-isolated inputs, and testing relays. The project intends to establish a developers community around the board.

Other I/O focused, Raspberry Pi based gear includes Cube-Controls’s Pi Cubes, which runs Ubuntu Snappy on an integrated Raspberry Pi, and Pimoroni’s Explorer HAT and Automation HAT. A more complete I/O controller system is offered by Techbase in its newly revised ModBerry 500.

Further information

The Raspberry Pi Mega-IO Expansion Card is available on Kickstarter starting at $25 through Oct. 1, with shipments due in March. More information may be found on the Mega I/O Kickstarter page and the Sequent Microsystems website.

(advertise here)

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2 responses to “Stackable Raspberry Pi home automation “X-HAT” aims for maximum I/O”

  1. Mihai Beffa says:

    Today the Mega-IO card passed the funding threshold on Kickstarter

  2. G. Como says:

    All I can say is that I have to wait. Extremely useful and compact. Is there a header with terminals that can be placed on the right angle headers? I am just thinking even the discrete device for IO would be better managed using terminals with screws.

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