I need help to choose SD Card Connectors

Semiconductor Integrated Circuits (ICs)
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1

Dear DigiKey Technical Support,

I am designing a portable backup device which is based on removable SD Cards and of course, a SD Card Connector/Slot.

According to the ST Micro datasheet, their MCU supports:

Data transfer Rate up to 208 Mbyte/s for the 8-bit mode of SDMMC bus.

STM32U575CGT6 STMicroelectronics | Microcontrollers | DigiKey

Now, my question is:

What kind of SD Card Connector should I choose so that the transfer speed is compatible with the ST MCU’s SDMMC bus speed?

I am new to this storage field. Please share your valuable experiences. I hope my device can transfer SD Card data as fast as possible so that it can survive a few more years on the market.

Yours faithfully,
Timmy

2

For this design (STM32U575CGT6) follow the MB1550-U575AIQ design files: 6L2S_Outjob the pcb routing is more important then the microSD connector (which is an off the shelf item)..

MB1550 uses: PJS008-2003-1 Yamaichi Electronics | PC Card Sockets | DigiKey Marketplace

Regards,

3

Hello RC,

Glad to meet you here. We talked a lot on Discord BeagleBoard. :grinning_face:

I will raise more questions later.

So, I do not need those 19, 21 pins SD Card Connectors for the current target speed 208 Mbyte/s for the 8-bit mode of SDMMC bus, do I?

4

STM32U5 only support 1 bit, 4bit and 8-bit up to HS200 (no HS400 and no pcie…)

image
image786×764 54.3 KB

So a standard:

9 (8 + 1) Position Card Connector Secure Digital - microSD

card slot is the best you can use.

Regards,

5

Hello Robert,

Thanks for your information.

To complete my project, I still need a certified Wi-Fi Module which supports Wi-Fi Direct p2p.

Would you recommend one? Low power is preferred for my portable device.

6

For Wi-Fi Direct check the module SDK, not only chip datasheet. Many chips support P2P on paper but vendor firmware for the module dont. Also take module with certification already done (FCC/CE) and stock at 2-3 distributors, for portable product the module is where you get stuck later.

How many units you plan first, prototype only or small series?

7

Hello sfzorin,

Thanks for your information.

I am looking for a Wi-Fi module for testing and prototype. My product will be a portable device.

Yes, you are correct. I have seen some Wi-Fi module which claims to support Wi-Fi Direct or P2P, but when it comes to the actual firmware, the factory cannot show additional information.

I am quite interested in TI’s modules but they cannot provide firmware supporting Wi-Fi Direct yet. :grin:

You have much experience on this issue. :smiley:

14

Hi @HKPhysicist when working with stm32 products take a look at their partnership products with Qualcomm: https://www.st.com/en/wireless-connectivity/wi-fi-products.html with the ST67W family they have good integration into the current STM32CUBE stack for software support.

Forgot it doesn’t have real WiFi-Direct as that was really a Broadcom thing.. but it does have multple Soft-AP support which you can make into WiFi-direct.

Regards,

15

RC,

I see. So they call multiple Soft-AP as Wi-Fi Direct, right?

I have downloaded the STM X Cube Matter. I will check it. Thanks.

16

Not exactly the same. Soft-AP is the module working as normal access point, phone must leave its own Wi-Fi and join the device network. Wi-Fi Direct is P2P with group owner negotiation, phone can stay on its home Wi-Fi. For a portable device soft-AP is often enough and every module supports it, so first check if you really need P2P.
One more thing, iPhone apps cant use Wi-Fi Direct at all, only Android. Which phones you need to support?

17

Dear sfzorin,

Thanks for the valuable information! You have helped me to save much time! :handshake: :folded_hands:

Actually, my primary target customer group is iphone boys!

I thought of Wi-Fi Direct because there is such an option on my Samsung phone.

Right now, I can focus on the SD Card IO. I will choose Soft-AP. I know how to implement it on ESP32. It is as simple as copying library from Arduino v2.3.

18

Which kinda leads to the other follow up i was thinking. Is there something specific in your design that requres the stm32? Using the SD controller on a ESP32 could be a way to optimze this design, and use your ESP32 knowledge..

19

Yes, you are correct.

Finally, I have found a very new ESP32-P4 which support UHS-I SDR104.

Damit! It is almost done! :smiley:

The next step is to find a reliable board of this ESP32-P4.

There is one made by RFRobot but I have bad experience with their ESP32-C6 board being not very reliable.

The same ESP32-C6 board made by Adafruit performs so much more stable! Of course, prices are more than double. :star_struck:

20

i’ve had pretty good luck with espressif own designed dev kits…

Regards,