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ZX Spectrum Multi I/O Interface - Fully Assembled

A fully assembled/tested Multi I/O Interface for the ZX Spectrum
Total Price: £62.50
Price excl. VAT (EU only): £62.50
VAT (EU only):
Price / 100 g:


The rights to the ZX Spectrum Multi I/O Interface has been acquired by DCS Electronics, please see their website here:






Model: ZXIO1


A Multi I/O Expansion Board for the ZX Spectrum giving Analogue Input/Output, Digital Input/Output and I2C expansion capability.


A Multi I/O board for the Sinclair ZX Spectrum.

Featured as a design project right here at this interface gives the Sinclair ZX Spectrum multiple I/O connectivity by way of an interface which plugs into the rear expansion port of the ZX Spectrum.

I never intended to sell this product as it was just a project for myself, however, there has been some interest so I have built up a few to sell, albeit at just over cost price.

  • ADC - 4 analogue inputs - 12 to 18bit configurable
  • DAC - 4 analogue outputs - 16bit
  • 24 digital I/O (8 outputs, 8 inputs, 3 on-boards LED's, 4 on-board jumpers & I2C)
  • I2C bus interface

The project page here describes the design in detail including the hardware & software.
Important: Please check it out, it gives far more detail on the interface that I don't want to simply repeat here. A knowlege of how to use the ZX Spectrum, ZX Spectranet card & Boriel ZX Basic Compiler is assumed.

What you get:

  • Fully assembled & tested ZX Spectrum Multi I/O board V1.0
  • USB flash drive containing a copy of the open source development software I collected during the project (Spectranet zmakebas, z88dk C Compiler, Boriel ZX Basic Compiler, ZX Spectrum TNFSD), and also the demo BASIC program I wrote which demo's how to program the interface.
  • Printed diagram showing the I/O connections.

What you DON'T get:

  • ZX Alioth Spectranet Interface. Required if you want to replicate my own DEV system. You can get them from various sources, i.e. here.



16bit Analogue Output = Range 0  to 5vdc (0 - 65535, actual minimum output voltage typically 0.05Vdc).
16bit Analogue Input = Range 0 to 10Vdc (0 - 65535).
Digital outputs = ULN2803 darlington logic buffer. Datasheet here.
Digital inputs = 10k pull-up to +5.3vdc, external connection via contact to 0vdc (GND).
I2C = Bi-directional I2C communication to further external Slave.

NOTE: The interface is tested with a 48K ZX Spectrum Issue 2 (Important: It is untested with other versions, I do know it doesn't work with the 128K Toastrack, I never got around to troubleshooting).



Here is the compete assembled board ready to plug into the ZX Spectrum / ZX Spectranet card.



This photo show the major components on the board and the designation of the screw terminals for the I/O.



Under development in my own workshop. The interface is plugged into the Alioth ZX Spectranet card (not included in the sale).





Ian Johnston Engineering Ltd.
VAT Registration No:   865 9910 71
Company Registration No. 288019

A VAT invoice (paid) will be supplied with every order.