Why does sending CMD58 over SPI to my Class 10 SD return 0x01 instead of 0x00?

Question

I am trying to initialize an SD card using an SPI bus and STM32F4 Discovery Board. I am mainly relying on Elm Chan's implementation of the disk_initialize function in the example code to base my own implementation. Unfortunately, I have run into an issue where sending CMD58 to the SD card during the initialization process return a result of 0x01, which implies that the SD card is idle. However, I am still seeing the next four bytes from the SD card as 0x00, 0xFF, 0x80, 0x00 which is in the right format for an R3 response. However, I am not sure if I can trust these four bytes as my OCR.

As of now, I have tried ignoring that the SD card is idling and simply tried to use the next four bytes as the OCR but the code seems to fail at other points during the mounting process with respect to the type of the card being assumed from the OCR.

if (Timer1 && SD_SendCmd(CMD58, 0) == 0) { 
      for (n = 0; n < 4; n++) {
        ocr[n] = SPI_RxByte();
      }  
      type = (ocr[0] & 0x40) ? 6 : 2;  
}

The code segment above is where I am first seeing the idle response. SD_SendCmd is where I send CMD58 to the SD card and where I am receiving 0x01 as the leftmost byte of the five byte response. Because I am not receiving 0x00, which signals that the SD card has no issues with the command passed to it, the code breaks out of the initialization process and returns an error. I would greatly appreciate any help with this matter as I have been stumped by this 0x01 return value for quite some time now. Thank you!

Is `SD_SendCmd()` synchronous? If no, then you probably need to implement a `while` to wait for it to finish. Similar with `SPI_RxByte()`. — virolino, Jun 17 '19 at 06:29
There is a significant difference between the bits and bytes. — 0___________, Jun 17 '19 at 06:49

score 0 · Accepted Answer · answered Jul 11 '19 at 19:16

So I was able to figure out the issue. It turns out that the card I was using was an SDHC card, where HC stands for high capacity. According to the simplified SD card specification, the CRC, which is sent at the end of the transmission of a command has to have the least significant bit set to 1. So, ORing the CRC with 0x01 before any of the transmissions let me initialize and use any type of SD card. So the issue I was having was not from CMD58, but how I was dealing with the CRC in general. Interestingly enough, not ORing the CRC seems to work fine with non high-capacity SD cards. But ORing the CRC with 0x01 seems to work with all cards (at least as far as I have tested).

score 0 · Answer 2 · answered Aug 06 '21 at 01:27

0

With regard to ORing the CRC with 0x01, this is not the CRC, but the STOP-BIT, the CRC is of type CRC7 and is at bits 1:7 of byte #6 in the command. According to the specification, even if the CRC is not required, the stop bit must always be 1.

answered Aug 06 '21 at 01:27

Mike

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Why does sending CMD58 over SPI to my Class 10 SD return 0x01 instead of 0x00?

2 Answers2