QL IO board?

[Pepperm]

here is a screen shot of a bit of the article.

[tofro]

That is - unfortunately - not so useful for the QL. This schematic apparently uses the handshake lines RTS/CTS and DSR/DTR of the 25-pin PC serial port to bit-bang I2C. The QL has only half of these and they are not particularily easy to control as you need to jump through hoops in software to switch them.