Unable to access SD Card using SDIO in F446RET6

[Abin]

Hai all,

I am using SDIO protocol for interfacing SD card with STM42F446RE.But While accessing the SD card, I am facing the following issues.

1. Unable to access the card, even the card size , free space etc

2. Also unable to open directory, and files.

Here I am using SDIO 4bit bus mode. FATFS enabled with minimum sector size 512 and maximum 4096.

I tried with external pull up resistors of 10k in each data lines(D0 to D3) and CMD lines.

Bit still I am unable to connect with SD card,

Please help me

[EZHON.1]

Abin,

Based on your reply, you want to use L476RG and F446RE to operate SDcard. But the Nucleo boards don't have SDcard slot for your applicatin.

So could you tell me your hardware connection with Arduino or Morpho connectors? which interface do you used: SPI or SDIO?

Thanks!

[Abin]

Hai,

I will explain my points clearly.

I have Nucleo f446RE board and I need to interface an SD card with the same board using SDIO protocol.

I am using SD card adaptor for connecting the SD card with Nucleo Board. Please see the image.

The connection is exactly the same as in the image.

I hope it is clear.

[EZHON.1]

Abin,

Thanks for your sharing. The schematic is no issue, even we can config internal pull-up/pull-down without external resistor to respect the SDIO specification.

I don't find the right MCU pinout for SDIO and the connection. But I think it's not the big issue if you checked them carefully.

I'm worried about the signal integrity because you used the flying wires for SDIO communication. For my understanding, it maybe the issue happens on the L446, but not on the L476. It should be better to use oscillator to confirm the signals.

If not, I suggest adding more GND wires close to SDIO signals to check if the SDIO communication can create.

[Abin]

Hai @EZHON.1 

Thank you for your reply. I will check it. Moreover, I checked the clock frequency. It is coming as 334KHz. I configured HCLK as 16 MHz from internal RC oscillator.And the division factor is 18.This division factor is derived from the following formulae

SDIO Need 400KHz clock, So 400 = (HCLK)/(2*(CLKDIV+2)).Please confirm , my approach is correct.

[Abin · Accepted solution]

Hai All, 

I want to mention my points about the SDIO protocol in the F446RE Nucleo Board.

1. First I checked the Clock frequency and verified that it is always 381 KHz all the times. The image from the oscilloscope is attached here.

2. Even if the frequency input for APB2 is divided with any prescalar value , the same 381 KHz is maintained.

It is not increasing or decreasing.

3. I have tested the same with an SDIO module which is purchased via online for hardware side verification. Unfortunately there is no change.

So , I assume that SDIO is not suitable for F446RE Nucleo or STM32f446RE microcontroller series.

Please give a response to my observations.