Tuesday, 29 September 2015

PET microSD new boards added to range

I've been updating the design of the PET microSD, and there are now three different versions to chose from, depending on how you want to connect it, and to what machine. All of these plug into the rear edge connector of a PET from a 2001 up to an 8032 (or variations of the 8032 such as the SuperPET 9000). See later for information on 2001-8 and 8032-SK support.
OPTION 1 - PET microSD v1.2 horizontal. The two boards at the top make up the original style board, currently on V1.2. This plugs directly into the IEEE-488 port on the rear of the PET. These are still available, and still the best choice for many users.
The board needs 5V power and that is supplied from the datasette port, with a passthrough connector to attach a datasette. This means it can be moved from PET to PET and does not need the case to be opened. Just plug the boards into the back.
The V2.0 boards provide some alternative mounting arrangements, and a few changes. Firstly, since these boards aren't sticking out the back, they don't need to be as small, so I've gone back to a slightly larger boards with all the parts on the top side, so the backs of the boards now only contain the serial number and firmware version info.
Secondly, rather than tap the 5V power rail, I've added a DC-DC converter on to the board, so it can be powered from any supply from 7v to 22v. There is a handy connector, J11 on the PET board, near the back of the case. This is designed to supply unregulated 9V to add on boards, such as the 64K RAM board.
The V2.0 PET microSD boards have a short cable with a 7 pin connector. 9V is on the centre pin, so it can fit either way around to avoid any problems. If you have a board which already uses this connector, I can supply a longer lead with a clip on the end to attach to one of the reservoir capacitors.
OPTION 2 - PET microSD V2.0 vertical. The first of these new boards is a vertical version, think ZX81 RAM pack, only slightly larger capacity and no RAM pack wobble.
This plugs into the back of the PET and the power cable plugs onto J11 inside the PET (2001N onwards). It takes up very little space and allows easy access to the microSD card. This is a good choice if your PET is close to the back of the bench.
OPTION 3 - PET microSD V2.0 internal. The second new board is much requested, one that can be installed inside the PET. OK. It's not entirely internal, there is no internal IEEE-488 header on most PETs, so it has a small loopback board that plugs into the back. I'll probably remove the pass through connector in the next version of this to make it half that size.
Inside the PET, the 18 way socket on the loopback board is just visible above the connector. There is just enough space for this to fit through easily,
The PET microSD fits onto this header and also the J11 power connector as before.
This is a good option if you want it hidden out of the way and don't need to remove the microSD card very often, or are happy to open the PET to change it.
This shows the PET microSD V2.0 internal mounted onto a 4032 board outside of it's case to get an idea of how it all fits together.
The 8032-SK and 8096-SK do not have rear edge connectors, but they do have the same 8032 board, and the edge connector is internal. This board is can be used internally in an 8032-SK, with the rear panel cable now plugging into the top of the loopback board.

PET 2001
All the versions of the PET microSD can be used with the original 2001, but 2001's with BASIC 1 need to be upgraded to BASIC 2 or BASIC 4, you can use one of my ROM/RAM boards to have a configurable BASIC 1/2/4 ROM and 8/16 or 32K RAM upgrade.
The original 2001 does not have the 7 pin connector, so I would have supplied a longer lead with a clip on the end, this attaches to the 9V rail, and the easiest place is on the leg of the reverse protection diode, the furthest leg from the corner of the board.


Which one do you choose? Well choose 1 if you want to move it around between PETs or easily remove it, or don't want to open the PET case. Choose 2 or 3 if you are short of space, or prefer less wires around the back. Choose 2 if you need access to the SD card, Choose 3 if you don't plan to change the card often, or are happy to open the PET as required. Not all PETs support all options, so see the table of which PETs support which boards, which also has buy it now links.