SD card interfacing with Atmega8

[sukhdeepmankoo]

Hi,
I am trying to interface SD Card with Atmega8. I have made the following connections on hardware side.

SD Card Atmega8

Pins Pins
1)CS 16(SS)

2)DI 17(MOSI)

3)GND

4)3.24V

5)SCK 19(SCK)

6)GND

7)DO 18(MISO)

Through MicroSD Adaptor.

On software Side, I have made Atmega8's software. Where Atmega8 is operating at 8Mhz.

void spi_init(void)
{ SPI_DDR|=(1<<MOSI)|(1<<SS_LOW)|(1<<SCK);
SPI_DDR&=~(1<<MISO);
SPI_PORT|=(1<<MOSI)|(1<<SS_LOW)|(1<<SCK)|(1<<MISO);
SPI_PORT&=~(1<<SS_LOW);
SPSR|=(1<<SPI2X);
SPCR=(1<<SPE)|(1<<MSTR)|(1<<SPR1);
}
unsigned char spi_transmit(unsigned char data)
{ SPDR=data;
while(!(SPSR & (1<<SPIF)));
data=SPDR;
return data;
}
void sd_spi_init(void)
{ unsigned char count,response=0;
unsigned int retry;
/***********wait for 74 clock cycles**********/
lcd_command_register(0x01);
delay(1500);
lcd_char_display("Initialization",LINE1+3);
SPI_PORT|=(1<<SS_LOW);
for(count=0;count<10;count++)
spi_transmit(0xff);
SPI_PORT&=~(1<<SS_LOW);
spi_transmit(0x40);
spi_transmit(0);
spi_transmit(0);
spi_transmit(0);
spi_transmit(0);
spi_transmit(0x95);
for(retry=0;retry<0xfffe;retry++)
{ response=spi_transmit(0xff);
if(response==1)
{ SPI_PORT|=(1<<SS_LOW);
break;
}
}
lcd_value_display(response,LINE4);
SPI_PORT|=(1<<SS_LOW);
spi_transmit(0xff);

SPI_PORT&=~(1<<SS_LOW);


lcd_value_display(response,LINE4);
for(retry=0;retry<0xfffe;retry++)
{ spi_transmit(0x41);
spi_transmit(0);
spi_transmit(0);
spi_transmit(0);
spi_transmit(0);
spi_transmit(0xff);
response=spi_transmit(0xff);
if(response==0)
{ SPI_PORT|=(1<<SS_LOW);
break;
}
}
lcd_value_display(response,LINE4+10);
SPI_PORT|=(1<<SS_LOW);
spi_transmit(0xff);


}

I am getting 255 on LCD Screen. why SD is not able to Initialize? Kindly tell me to find where i have done mistake.

Thanks & Regards

 

[shato]

Hi,

only to say you, that some cards can cause troubles.

example :

I have interfaced a sdcard DAN-ELEC with my atmega 8 ==> ERROR (error initialisation).

Voltage was 3.3v

Everything seems OK (with electronic oscilloscope) : SCK,MOSI,MISO,SS

I spend a lot of time...

Finally, I tried another SCARD , and , it was OK !! (3,3V and 5V too)

So, I'd like to find the datasheet of the sdcard DAN-ELEC 2Go, to understand what was the problem.

Perhaps no, you found the solution...

Good luck.

BErt