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hoglet67 / MMFS

Modern SD Card File System for Acorn 8-bit Machine (Master, Beeb, Electron)
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TurboMMC schematic and PCD #32

Open 68ec020 opened 1 year ago

68ec020 commented 1 year ago

I noticed there is just a hand-drawn schematic and no PCB layout for the TurboMMC interface. So, I created one:

https://github.com/68ec020/uSD-Turbo

I will add a readme file soon, but feel free to link to the repo in the MMFS wiki. The interface is working and I included resisters everywhere two outputs could be active at the same time, like in the hand-drawn schematic. So it should be safe.

uSD-Turbo
StormTrooper commented 4 months ago

Thanks for posting this. I'm trying to build one of these. Has this been confirmed working?

I've looked at the hand drawn schematic posted and there are a bunch of extra 1k8 and 3k3 resistors so wondering why these are missing?

68ec020 commented 4 months ago

Hi StormTrooper! The hand-drawn schematic uses voltage dividers to generate 3.3 V signals for the SD-card. I used an active level shifter (74LVC125AD). Also, there is no information in the hand-drawn schematic, how VCC (3.3 V) for the card is generated. On my board there is a voltage regulator. I use this board in my BBC Micro and it works. To be completely honest the board I use and tested is an earlier version. I realised R5 was missing on this earlier PCB version and I added a leaded resistor to the connector to fix it. The only change to the latest version on Github is the missing resistor. I was too lazy to order and build I new PCB just because of this. If you need help with building / ordering a PCB, please ask again. Maybe on my repo, so we don't spam this one. I would love to hear if the interface works for you.