Can someone help me with interfacing the eMMC flash chip with the RPi and the micro SD card slot? I have some problems with available micro SD cards and noticed that the eMMC can be used just as the micro SD card, but it has to be in the TF format. Something like this:
Now, it is ok to buy it from AliExpress, but I wonder how to make my own design based on the Samsung KLM8G1 flash chip.
The SD card has pins:
DAT0/MISO
DAT1
DAT2
DAT3/CS
MOSI
CLK
VSS
GND
The Samsung KLM8G1, however, has many more pins, although the huge majority are not used at all. Of what are used, there are:
VSS
VCCQ
VDDi
CLK
RST
DAT0-7
CMD
Data Strobe
On the board from Aliexpress, there is a flash chip, an LED with a resistor, another resistor of 4.7K, and a few capacitors. I have no idea how it is connected, and how can I replicate this. It does not have to be this flash chip at all.
I believe I could just add, eventually, the LED with a resistor, and maybe a few more caps. The RST here is pulled up without a resistor, which is ok, I think.
If you have never done a PCB design with a fine pitch high speed BGA, I suggest you forget trying to do you own design. Proper layout will be critical for this design to work.
Turning eMMC into a drop‑in replacement for a micro‑SD card sounds cool, but it’s far from plug‑and‑play. A micro‑SD card only has eight lines (DAT0‑DAT3, MOSI, CLK, CS, VCC, GND).
The Samsung KLM8G1 eMMC device you mentioned exposes many more signals – separate core and I/O power rails, reset, DAT0‑DAT7, CMD and a strobe line.
That means you’re dealing with a fine‑pitch BGA package that’s meant to live on a high‑speed PCB. You can’t just solder it to an SD socket and expect it to work; the routing, trace impedance and bypassing need to be right for reliable operation.
That’s why one of the forum replies bluntly said: if you’ve never done a PCB with a high‑speed BGA, forget about rolling your own – proper layout is critical. The ready‑made adapters you found on AliExpress do that work for you
I agree that designing a high-speed PCB for an eMMC flash is something that can be called a level above my knowledge.
But…
Yoda said: Do, or do not. There is no try. Here, where I live, there is something called inat, which can not be easily translated into any language on the planet Earth.
By just saying, please don’t even try, basically means, if you ask, you’d better leave it. If you ask, it means you have no idea. I once asked what fuel to poor in my car. I once asked how much one apple is, plus another one. You must learn once.
Maybe the question is not for a forum. Or maybe some guidelines could do the job.
marcgiroux85 said there is an adapter on Aliexpress that can do the job. Yes, there is. Someone made it. It can be made. Enough for me.
You can always fix a tire or pay a guy to do it for you.
For every single question here, you can answer just the way you answer me. I am sorry, but this is BS. Have you ever asked a question in your life? For anything?
The knowledge level is not fixed. It is up to you to gain a level after level. To do so, you must learn, ask, and try. If you quit every time someone says to you to let others do it for you, you are doomed. Maybe it is your way of thinking, living life, etc, but it is not mine.
Please, stop lecturing me should I try to design this kind of PCB. You can help, or you can pass this topic.
