Cannot Initialize 8GB SDHC CMD8 responds with (0xFF)

Question

I am trying to interface a 8GB SDHC with STM32L0 controller through SPI.

Followed this tutorial.

As this thread suggests, I followed the the Command Sequence as follows:

1. CMD0 arg: 0x0, CRC: 0x95 (response: 0x01)
2. CMD8 arg: 0x000001AA, CRC: 0x87 (response: 0x01)

I am sending some clocks with CS Activated and Deactivated in between these commands as discussed here.

Somehow, I get the response from CMD0 as 0x01 but CMD8 always responds with 0xFF.

Following is the code I am using to init my SD card:

void SD_INIT(void){
    CS_HIGH;
    for(count = 0; count < 8; count++){
            SPI_SEND_CMD_DUMMY();
    }
    CS_LOW;
    for(count = 0; count < 8; count++){
            SPI_SEND_CMD_DUMMY();
    }

    uint8_t txBuff[] = {0x40,0x00, 0x00, 0x00, 0x00, 0x95 };
    HAL_SPI_TransmitReceive(&hspi2,txBuff,readBuff,6,100);

    //count = 255;   //Try 255 times..
    for(count = 255;count>0;count--){
            uint8_t dummy[] = {0xFF};
            HAL_SPI_TransmitReceive(&hspi2,dummy,readBuff,1,100);
            if(readBuff[0] == 0x01){
                    status = 1;
                    break;
        }

    }

    for(count = 0; count < 8; count++){
            SPI_SEND_CMD_DUMMY();
    }
    CS_HIGH;
    for(count = 0; count < 8; count++){
            SPI_SEND_CMD_DUMMY();
    }


/*-------------------SDHC TRY----------------*/

    if(status==1){

    //status=0;
    CS_LOW;
    for(count = 0; count < 8; count++){
            SPI_SEND_CMD_DUMMY();
    }
        //HIGH CAPACITY 0x000001AA 
    uint8_t tx1Buff[] = {0x48,0x00, 0x00, 0x01, 0xAA, 0x87 };
    HAL_SPI_TransmitReceive(&hspi2,tx1Buff,readTempBuff,6,100);

    //count = 255;   //Try 255 times.. //10ms = 160000
    for(count = 100;count>0;count--){
            uint8_t dummy[] = {0xFF};
            HAL_SPI_TransmitReceive(&hspi2,dummy,readTempBuff,1,100);
            if(readTempBuff[0] == 0x05){  //Invalid Command
                    status = 3;
                    break;
        }
    }

    for(count = 0; count < 8; count++){
            SPI_SEND_CMD_DUMMY();
    }
    CS_HIGH;
    for(count = 0; count < 8; count++){
            SPI_SEND_CMD_DUMMY();
    }
    }

void SPI_SEND_CMD_DUMMY(void){

        uint8_t txBuff = 0xFF;
        HAL_SPI_Transmit(&hspi2,&txBuff,1,100);
}

The response I am getting in readTempBuff is:

readTempBuff[0]  :  0xFF
readTempBuff[1]  :  0xFF
readTempBuff[2]  :  0xFF
readTempBuff[3]  :  0xFF
readTempBuff[4]  :  0xFF

Answer 1

for(count = 100;count>0;count--){

That is only 100 response bytes, my code uses 1000 for every SD command. Some cards may need the extra time/clocks.

Note that IIRC you also need to process the R7 response of the CMD8.

SDHC card code is non-trivial, but there are a lot of open source implementations to learn from.