Pi HAT with 16 opto-isolated inputs can stack for up to 128
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Monarco HAT - Analog and digital I/O, RS-485 and 1-Wire bus for Raspberry Pi
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I/O Accessories Kit for I/O Learning Card for Raspberry Pi – Sequent Microsystems
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IO Expansion HAT for Raspberry Pi Zero/Zero W - DFRobot
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Monarco HAT - Analog and digital I/O, RS-485 and 1-Wire bus for Raspberry Pi
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Waveshare Stack Hat For Raspberry Pi, Stacks Up To 5 Hats, I/o Expansion Kit, 5 Sets Of 2x20 Pinheaders, Usb External Power Port - Demo Board - AliExpress
IO Expansion Hat for Raspberry Pi 3/4/400 - DFRobot | Mouser
Universal Plus Raspberry Pi Hat - The most advanced I/O Hat | Facebook
IO Expansion HAT for Raspberry Pi 4B/3B+ - DFRobot
IO Expansion HAT for Raspberry Pi 4B/3B+ - DFRobot
