Use FREE-SHIPPING discount code for all US orders over $15


What payment methods do you accept?

We accept the following credit cards: MasterCard, Visa, American Express and Discover. We also accept payment by PayPal or Amazon Pay. If you decide to use either of these two methods, you’ll be taken to either the PayPal or Amazon Pay website, where you’ll be prompted to log in and process your payment. You’ll then be directed back to our merchant website once your transaction is complete.

You can also pay by wire transfer or by check. You can select any of these methods at checkout. 

To request Net-30 terms please send a valid purchase order on your company's leterhead to

Where is my refund?

We aim to process refunds within three days of an item being returned to us. Please note, however, that your bank may take several days to process the payment back into your account. With that said, please allow up to ten working days after posting the item back to us before getting in touch about your refund. 

Ordering and delivery

Can I place an order without creating an account?

Yes. You can place an order as a guest with no obligation to create an account. However, we do recommend that you create an account in order to be able to check your order history. We also recommend that you subscribe to our email newsletter, in order for us to notify you of bug fixes, new products or enhancements. 

Click HERE to create a new account.

Where is my order confirmation?

This is automatically sent to your email address when you place an order. If you haven’t received your order confirmation within 24 hours, please get in touch at just in case there’s a problem with your order. Please check your mailbox’s spam or junk folder before contacting in case the order confirmation has been diverted there.

How do I cancel my order?

There is only a short amount of time between when you place your order and when we start processing it. If you contact us straight away after ordering, via, we may be able to cancel your order before it’s processed. If not, we’ll despatch your order and then you can return it to us if you wish upon receiving it.

Can I alter my order?

If your order has not been dispatched, send an email to with the required changes and we'll try to adjust. We will send a refund or invoice if there is a difference in cost.

When will my order arrive?

Orders that require shipping within the U.S. will be delivered within three to ten days, depending on your preferred shipping method. Shipping to countries outside of the U.S. may take up to 14 days. Please get in touch if your order hasn’t been delivered according to the expected timescales, and we will check your order status.

What countries do you ship to?

We ship to most regions worldwide. You can select the shipping carrier at checkout. USPS usually delivers in 7-20 days to most countries, while UPS or DHL can deliver in 1-3 days.

How much is shipping?

Shipping costs depend on the item you’ve ordered and the country where it’s being delivered and it is calculated at checkout. 

If your order value is more than $15 we provide free shipping within the U.S. After placing your order, enter the code FREE-SHIPPING at checkout.

Can I track my order?

Yes. We’ll provide updates at every stage of your order, from the moment you place it, through to despatch and delivery. In your delivery confirmation emails, you’ll receive a tracking reference which you can use to check the progress of your order online.

Technical Support

Can your cards be intermixed? How many?

Theoretically, all our stackable cards can be intermixed in almost any configuration, up to eight of each type. 

In practical terms, stacking more than eight cards becomes mechanically challanging.

What is the maximum signal frequency on digital input ports?

At this point six of our cards can process digital inputs. The maximum frequency of input signals, or transitions per second that can be sensed, is the following:

  1. Home Automation Card has 8 optocoupled inputs prepolarized at 5V and can count transitions up to 125Hz.
  2. Industrial Automation Card has 4 optocoupled inputs that can count transitions up to 500Hz
  3. Building Automation Card has 8 dry contacts inputs that can read signals up to 500Hz

The following cards can read both AC and DC signs have a low pass filter at 25 Hz and can count up to 10 transitions per second:

  1. Sixteen Digital Inputs Card, which can read 16 AC/DC signals from 3V to 24V
  2. Four Relays four Inputs Card, which can read 4 AC/DC signals from 3V to 240V
  3. Eight HV Digital Inputs Card, which can read 8 AC/DC signals from 3V to 240V

What GPIO pins are your cards using?

All our cards use only the I2C pins from the Raspberry Pi GPIO connector to communicate with Raspberry Pi, leaving the other 25 pins available for your use.

Cards with on-board watchdog control the power to the Raspberry from the local processor. If the watchdog is activated, power is cut off if Raspberry does not access the I2C port in the preset time interval.

Cards with RS485 tranceiver use also one serial port of the Raspberry Pi. If enough resources are available, the RS485 port might be connected to the local processor as well, and jumpers are provided to decide who is controlling the transceiver.

Cards on on-board push-button have the push-button connected to pin 37 of the GPIO connector. The push-button is also connected to the local processor, if present and enough resources are available. 

Cards without a processor use I2C expanders to control the I/Os.

The only exception to all the rules is the I/O Learning Card, which uses the resources of the Raspberry Pi and is not stackable.

Sequent Microsystems GPIO Connector for Raspberry Pi HATS

Do you sell your product abroad or only in the US?

We sell worldwide. For small orders, the cheapest shipping carrier is USPS, which will pass the package to your local postal service.

For larger orders we use UPS and DHL. Shipping cost is calculated at checkout.

Do you have RoHS and REACH Compliance Declarations for your cards?

We keep RoHS and REACH Compliance Declarations on file for all our cards. If you need a local copy you can download it here:

Building Automation 8-Layer Stackable HAT for Raspberry Pi

Eight HV Inputs 8-Layer Stackable HAT for Raspberry Pi

Eight MOSFETS 8-Layer Stackable HAT for Raspberry Pi

Eight Relays 8-Layer Stackable HAT for Raspberry Pi

Four Relays four Inputs 8-Layer Stackable HAT for Raspberry Pi

Home Automation 8-Layer Stackable HAT for Raspberry Pi

I/O Learning Card with Full Node-RED Tutorial for Raspberry Pi

Industrial Automation 8-Layer Stackable HAT for Raspberry Pi

RTD Data Acquisition 8-Layer Stackable HAT for Raspberry Pi

Sixteen Digital Inputs 8-Layer Stackable HAT for Raspberry Pi

Sixteen Relays 8-Layer Stackable HAT for Raspberry Pi

Smart Fan HAT the Best Cooling Solution for Raspberry Pi

Super Watchdog HAT with Battery Backup for Raspberry Pi

Three 40A/240V Relays RS485 Daisy-chainable HAT for Raspberry Pi

How do I connect my load to an Open Drain Output?

The following diagram shows how to connect your load to any of our cards with an open drain output. You have to provide the power supply and to connect the load as shown. Make sure the DC voltage of the power supply does not exceed the specifications of the card.

Open Drain Loads

Can you stack a Home and an Industrial Automation board?

Yes, you can stack them, but mecanically the Home Automation card needs to be on top of the Industrial Automation card.

Since each card can be stacked to itself, you can stack up to eight Industrial Automation cards on top of the Raspberry Pi, and add up to eight Home Automation to the assembly.

Can I use Sequent Microsystems I/O cards with ROCK PI 4 ?

Yes, you can use all our cards with ROCK PI 4.

Because our drivers are made for Raspberry Pi, some changes need to be made.

Here a step-by-step example for setting up your ROCK PI 4 for using the  Home Automation For Raspberry Pi Card :

1) Install Debian  (u/p:rock/rock)
2) Install mraa library :
3) Turn on the I2C port  sudo nano boot/hw_intfc.conf   | turn on i2c7
4) Install build tools: sudo apt-get install build-essential python-pip python-dev python-smbus git
5) Get the repository: ~$ git clone
6) Change "/dev/i2c-1" with "/dev/i2c-7" in ioplus-rpi/src/comm.c
7) cd ioplus-rpi/
8) Install the ioplus command line interface: ~/ioplus-rpi$ sudo make install
9) Connect the card and test the software ioplus -list shuld return the cards connected to the ROCK PI.


My Question is not here. How can I get an answer?

Please use the Contact Us form to send your question, or email us to

We answer most inquiries in 24 hours, and if your question is of general interest we'll post the answer as well

Can I use interrupts to read inputs, or do I have to poll?

You can use intrerrupts on Raspberry Pi, but you have to write your own interrupt handler and activate the GPIO pullup, which is 50K to 65K.

Our cards with digital inputs send an interrupt signal to Raspberry Pi on input transitions.

Cards with analog inputs can be programmed to interrupt on input thresholds.

16 Inputs V2: GPIO11, Pin 23; V3 (Easy): GPIO26, Pin 37

8 Inputs V1: GPIO05, Pin 29; V2: TBD

12 Inputs V1: GPIO26 (Easy), Pin 37

4 Rel/4 Inp V2: N/A; V4 (Easy): GPIO26, Pin 37

RTD V6: N/A; V7: N/A; V8 (Easy): GPIO26, Pin 37 (use PA0)

HOME V1: N/A; V2 (Easy): GPIO26, Pin 37 (use PA1)

IND V3: GPIO13, Pin 33; V4 (Easy): GPIO26, Pin 37

BAS V4: GPIO10, Pin 19; V5 (Easy): GPIO26, Pin 37

Is there a way to automatically detect 1 or more Sequent I/O cards, and their types and addresses, without actually importing/using the drivers?

Considering all Sequent I/O cards communicate I2C, you can scan the bus for attached devices and detect which cards are connected and what stack-level settings they have. One little problem here, there are a few cards (we started replacing them) that use the same IO expander chip, so you will not be able to detect the exact type of the connected card. Here is the list of the I2C addresses for all cards, including the obsolete ones.

Do you have "C" libraries for your products?

We did not have a C library for our products but the command line interface is written in C and the source code is available on GitHub
You can decide to make your own library or use the code as it is but either way is very easy and you can count on our support.

Do you have any distributors in Europe?

  • in Germany
  • in England
  • in Czekia

Can your boards also be used with the Odroid C4 SBC's?

We did not test our cards with odroid but we think it will definitely work. The 40 pin connector for Odroid and raspberry are electrically identical. We have a Python library and command line interface written in C  which can be used on any linux os . All our cards use I2C port for communication , on raspberry i2c-1 and on Odroid i2c-0, so you need to change the port number in the source code.

How many Sequent boards can I install on one Raspberry Pi?

All our cards are stackable to eight layers, with a few exceptions

  1. 3-RELAY card can be only daisy chained through the RS485, it is too thick to be stacked
  2. Super-watchdog is not stackable since it does not make sense
  3. Smart Fan is stackable only to two layers

Some "dumb" cards implemented with I/O expanders (8-RELAYS, 8-INPUTS, 16-RELAYS, 16-INPUTS and 8-MOSFETS) share the same I/O address due to market shortages, so they can be stacked only up to combined eight.

The other "smart" cards can be stacked eight of each. This means you can create unreasonable long stacks. 

We tried to find if there is a practical limitation caused by the I2C communication. We tested a stack of 30, which is unreasonably long, and it worked without a glitch. How many HATS on one Raspberry Pi?

How can I use your cards with Beagle Bone using your Beagle-Pi Raspberry Pi emulator?

In order to use BB with our cards, there are some steps to follow. They are described on the  Beagle-Pi Raspberry Pi Emulator Using Beagle Bone Black page under SOFTWARE tab.
Here are the essentials:
To temporarily enable the I2C on Beagle Bone, open a terminal and type the following commands:
config-pin P9.17 i2c
config-pin P9.18 i2c
Depending on your OS, you might have to use the commands:
config-pin p9-17 i2c
config-pin p9-18 i2c
To enable the I2C permanently at startup, edit the file /etc/rc.local and add the same two lines. All the command "exit 0" on the last line.
To use the Node-RED, which comes preinstalled on the Beagle, add the Node-RED to the I2C group with the command:

sudo usermod -a -G i2c node-red

How fast can I read a signal using your digital input boards?

All our digital input cards have opto-isolated inputs.

In order to also read AC signals, we filter the signal at the output of the optocoupler.

The cards without a processor have a hardware filter. The cards with a processor filter the signal in software.

The cards without a processor can read signals up to 12Hz, square wave 50%. This group includes: 

  • 16-LV-INPUTS

The cards with a processor can read signals up to 4Khz, and measure PWM signals up to 500Hz. This group includes:

  • Home Automation
  • Industrial Automation
  • Building Automation (universal inputs not optocoupled)



How can I set Raspberry Pi time from the Sequent Microsystems Card RTC

To set the Raspberry Pi time from the RTC for the Industrial Automation card, run the following command from the command line or from cron:

t=$(megaind 0 rtcrd) | sudo date --set "$t"

Change the megaind command with the appropriate one for the card you use. 

We wrote a full script which keeps the two systems in sync. If the network is active, it sets the RTC time from Raspberry Pi.

If the network is down, it sets the Raspberry Pi time from the RTC. You can download the script from GitHub, with instructions HERE.