Full size SD Card Reader Prototype

Hi All,

i’m working on a Full size SD Card Reader to fit into the expansion card, let me know if someone is interested to help out mechanic design and firmware design. My FW is a bit rusty because in the last time i mainly do HW electronic development :slight_smile:

I finally manage to find all the electronic parts needed to do a USB C to SD card reader and i will have the schematic finished soon.

The hard part where the connectors, but with some mechanical modification i think i solved the connector problem: see attached pictures:

Things to do:

  1. Schematic ( this is no problem)

  2. Final Mechanic design → where to put screws on outside

  3. FW design for the IC ( there are some examples, i think they just need to be adjusted to my HW)

  4. Optional dual SD FUll size connector + uSD connector in same expansion card
    ( the connector will fit and the IC supports dual SD, only need to check layout if all electronic parts fit to PCB)

What do you think?


The best bet is to use the two screw posts for the PCB since everywhere else is occupied with either the IC or the SD slot but instead of leaving a giant air gap between the top and the pcb use spacers/washers. The other (card insert) side might get away with a simple “clip” or a stud design that prevents it from opening in that direction, or none if the cover is recessed into the case (e.g. preventing easy prying action on a open seam without the use of a flathead or a tool).
I would be using recessed screws on a non-exposing surface.

I will throw money at this.


Agree. Full sized SD have so many good things about it, small SDs don’t cut it.

I wanted a PCIe card reader, though. Can you handle that?

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The tolerances will be way too tight, 3D printing tends to have +/- 0.5mm and there is not enough room for circuitry. I would suggest a larger expansion card.

This looks like a very solid design…

Would throw :heavy_dollar_sign: :heavy_dollar_sign: behind this…

I’m no expert but couldn’t you use the same IC and firmware from the original microsd card (if available) and just connect it to a full size sd rather than the microsd physical port on your custom pcb?

Idea: Combo with full-SD and mini-SD in the same dongle. Mini on top, Full on bottom, for example.


  • How do you mean that? Do you have an example?

“The other (card insert) side might get away with a simple “clip” or a stud design that prevents it from opening in that direction, or none if the cover is recessed into the case (e.g. preventing easy prying action on a open seam without the use of a flathead or a tool).”

  • What exactly do you mean by PCIe card reader?


I can provide the model, and you can check if this could be 3D printed ?
I would go for a aluminum housing CNC drilled


i don’t know what IC did they use in official uSD card reader ( i still can’t order the laptop to my country)

Maybe, as i said before the IC support dual SD cards, but i have to check if all the components fit to the PCB


Your not getting aluminium cnc drilled, it’s probably worth 40 bucks to get it drilled and cleaned up.

I’m curious what bridge chip you selected. I was looking for something to build my own before I saw this thread. I was looking at the Prolific PL2731 or the Realtek RTS5307, but one or both are EOL and hard to source from the normal suppliers. In the end I was considering the Cypress CYUSB3025.

Yes the Cypress CYUSB3025, it is available and in production, and the documentation is available, also there are some FW examples that can be reused.

I have experience with cypress FX3 and CX3 HW design, and SD3 is similar.

there is also VUB300:

but this doesn’t support dual cards, but i think this doesn’t need custom firmware

I don’t know how to do a 3D CAD (yet), but I have a rough idea of how to draw a 3-view diagram. Let me do that.

I felt this is pretty explanatory. I don’t need to draw a top-down or a frontal view.

The top image is what I will call a “base”. You have the hollowed out case, and you would put your PCB in. You have a big slot for the SD card, and you make two tiny slots.
The bottom image is what I will call a “cover”. You have the two “tabs” that stick out, which will go into the tiny slots in the above picture. The cover is installed with the “tabs” first lining up with the “slots” first going in, then “closing” the cover and fix it at the other end with two screws.

So the far end is fixed with screws and this end is secured using the tabs. Note that the lid might still “wobble”, but because the tab is preventing it from lifting off, it is secured in place.

If there is not enough room for making separate slots, you can make two little notch in the card opening itself and the two “tabs” will go in there.

By PCIe card reader I mean a card reader that interfaces with the system via PCIe, rather than USB.
Something like this
PCIe card reader example
or this thingy from walmart
However because we are interfacing with Thunderbolt instead of raw PCIe from the bus, I think this will be quite difficult to pull off, and a Thunderbolt card reader is quite a bit overkill.

Having to go to PCIe from TB4 is challenging considering the bridge chips are 20-30 dollars. Not even considering manufacturing costs as they use BGA.

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I don’t think even UHS-II (2) SD cards would require anything beyond USB 3.0 or maybe 3.1 or 3.2? Now if you were talking CFExpress, there are requirements for TB3/TB4.

I wonder if chopping the cable off this and putting the male USB-C connector directly on the board (depending how thick the controller is under the SD slot) would allow a fairly straightforward conversion?

I don’t know. But Dell 9360/9350 actually have a PCIe SD card reader with … yeah. not unworldy speeds (something like 500MB/s)
Check this from NotebookCheck.net
It will, however, allow some niche like SD card boot (since it’s not interfaced with any USB anyway)

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Hi, just wondering if there are any updates on this or what the roadmap looks like. I’m 100% okay with waiting however long it takes, I’m just curious to know how it’s going.

I can help if needed or just complete it on my own.

Hi All, sorry for late update, i’m building this in my free time and i had to sort out some personal things, nevertheless here’s an update:

  1. You can find the schematic on the link below:

→ for firs prototype i decided to go with VUB300 because it don’t require any custom FW development like the Cypress CYUSB3025-BZXI.
→ the down side is the VUB300 is only per SDIO spec 2.0 and USB2, while the CYUSB3025-BZXI is SDIO spec 3.0 and USB3 ( i need to figure out how to modify sample of the FW for CYUSB3025-BZXI in order to get this working)

  1. there is the problem with the connectors, because i found only few company that produce them ( need these connectors in order to fit to the expansion card size), the connectors have a MOQ of 3000pcs, at the end the company agreed to provide 3pcs sample but the shipping to me it will cost 100$ + Import duties + tax.

→ i would like to measure them in real, i found something similar in ebay and waiting to arrive.
→ or i need to find some one in china to get the samples to their address, and then post me via standard mail.

as Josh_cook sad you need a TB controller to get the PCIe lanes.
We could use TB3 IC that is cheaper, consumes less and is smaller than TB4 IC, because TB4 comes only in DUAL/QUAD config while the TB3 is also in SINGLE config
Thunderbolt™ 3 Controllers Product Specifications (intel.com)
Like JHL6240 ( the question is how to get the documentation to design it in)

Other thing is does it have to support standard Sd cads( then probably we need additional PCIe->SDIO bridge) or only PCIe sd cards like SD_HC_I_Express? ( i have to look in to that how that actually works)

if you like you can review the schematic :slight_smile:


Do you understand the USB spec? You need a 4.7k ohm resistor on CC1