Tuesday, 4 July 2017


Nothing much to say about this at the moment. Though this will be a cartridge port version of my internal RTC boards mentioned in THIS post a few days back.

The little RTC boards will solder into this PCB and be used that way. I did wonder about having the circuit on this cartridge PCB, but the problem is, as always, cost.  If I stocked the RTC boards and this board, then I would have to buy twice as many RTC IC's and with them being around £10 a go, I just don't want to keep investing huge sums of cash into things which may never sell.With that in mind, I can have produced just a few of this cartridge boards at a time and re-use the RTC mini boards.

The PCB will plug into the ST's cartridge port as normal. I added on a "through" connector on the end so other cartridges can be used. Though the problem is I can't find new 40way edge connectors like used on the ST's motherboard. So I will have to re-use them off scrap boards for now.  As more than 10 of these are unlikely to ever sell, then I don't think its a huge problem anyway.

As for "cases" for these. It is not something I myself have time to look into doing. Though there have been a few people offering to design a case for them. So it will be up to the community to design & produce cases for these.

I don't know when these cartridges will be produced. This is more of a "side-line" project for me. So keep checking my blog for updates on various things and don't forget to subscribe :)

Work is ongoing faster than posts are being added to my blog :)

I have sent off for 3 prototypes, expensive as I used 4 layers in the design. I didn't want to risk grounding bounce issues so 5V and 0V have their own layer. Signals are routed on the other 2 layers. In fact copper fill is filling in 0v also.  I've slapped on there a 100uF ceramic.  Will help stop voltage drops for carts powered through this RTC cart.

Hopefully will be some more news in the coming weeks..


  1. any source Kicad/eagle available for the ST cartridge port ?

  2. Not that I know of. I think that was a standard edge connector I used.