Sinclair ZX80 / ZX81 / Z88 Forums

I'd like to send and receive data to and from a ZX Spectrum from an external device with a serial port. Can anyone suggest a circuit for adding a serial port to a ZX Spectrum?

Would a parallel port work better w.r.t how BASIC reads and sends bytes? It looks like from the ZX side a parallel port with a specific address would be best for reading and writing. I can then simply convert between parallel and serial using a MAX232 and some shift registers.

Ideas?

The Sinclair Interface 1 includes a bit-bashed serial port. It uses a 9 pin D-connector, but with non-standard pin-out.
SPECTRA also includes an Interface 1 compatible serial port.

If you want a DIY system, the difficulty is the range of UART serial chips is rather limited these days. Zilog’s version is still available and Motorola’s version can be obtained from eBay etc. But a lot of the other UARTs are rather harder to get these days.

Alternatively, rather than using a UART or shift registers, a suitably fast microcontroller can do the serial to parallel conversion.

A bit bashed solution is easy in hardware, but requires more complex software.

dr beep has developed a parallel interface to connect to a PC Centronics port.

But any DIY system will require software to be loaded in order to use the new hardware...

Mark

I was actually gifted recently three or four 8250 UARTs. Could they be useful?

I can program an Arduino to do conversion too. I was just looking for ideas. Thanks 1024!