Sunday, 4 January 2026

Minstrel Expansion Bus Roundup

This is a quick overview of where things are with the Minstrel Expansion Bus.

There are now three modules and another couple in development, and two backplane options.

There are also various other boards which can be used with it, such as the Minstrel ZXpand:

And David Stephenson's ZX-IO:

Backplanes

I have recently updated the backplane options, so there are now two versions, powered and unpowered.

Previously the unpowered version was the same PCB as the powered version without the power supply bits fitted.

But now there is a dedicated unpowered version with just the bus connectors.

Available with a pin header for direct soldering to a Minstrel 2 or 3.

Or an edge connector to attached to a Minstrel 2, 3, ZX81 or TS1000.

This version is powered by the host, so that is fine for a few lower power cards.

If you plan to add more cards, the powered version is a better option.

This does two things. Firstly, it has a 7805 5V regulator which powers all the slots, plus the rear pass-through connector.

Secondly, it has a 9V DC input. You can either have this completely separate, and use it to power the slots and the 7805 and leave the host as it was. 

Alternatively, you can jumper it to connect to the hosts 9V rail. That allows you to supply power to either the 9V DC barrel jack on this board, or the power jack on the host.

This is most useful if you are using a ZX81 or TS1000, so you can avoid using the less than ideal 3.5mm DC power jack on there.

Having the bus connectors powered by their own regulator also avoids any additional load on the hosts 7805 regulator, which often gets quite toasty all on it's own if it's a ZX81 or TS1000.

The passthrough edge connector is also powered by the 7805 on the expansion bus, so you can use larger peripherals without overloading the host power supply.

Or even anther backplane if you need more slots:

Or a powered and unpowered combo:

The Modules

The number of modules is building up, with a few new ones in development, and ideas for several more.

Oops, pretend you didn't see that one yet.

I'll put a different one in, no one will notice.

Minstrel Joystick

The first module of this type was the Minstrel Joystick

This is a Kempston compatible joystick interface, for use in your own programs with a bit of simple machine code, or in games such as Paul Farrow's ZX81 Kong etc.

Minstrel Input Monitor

This started as a request to add a click when you press a key (like the ZX Spectrum), but grew to also include a monitor for the loading signal.

Minstrel ROM Cart

This is a new module to replace the internal ROM with multiple jumper selectable ROM images.

Minstrel ZXpand

Although not originally designed for it, the Minstrel ZXpand fits into this system, either as a vertical card, or on the rear expansion slot.

If you do attach it like that, you still need the wire to connect to the mainboard to select the ZXpand ROM.

Although you can replace that functionality with the new Minstrel ROM cart.

That means you can now use the Minstrel ZXpand on a ZX81 or TS1000 (internal RAM upgrade required)

Adverts

The various backplanes and modules are available from my Tindie store, as kits or assembled.

Patreon

You can support me via Patreon, and get access to advance previews of development logs on new projects like the Mini PET II and Mini VIC when I get back to them in the new year and other behind the scenes updates. This also includes access to my Patreon only Discord server for even more regular updates.

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