msp430f5438 - writing on SD card (slaa281b)

Thanks Jens, one more question though, do SD cards have seperate CD pin in SPI mode? We are connecting DI,DO,SCK and CS pins to MSP430, with also Vcc and 2 Gnd pins. We could use a pull-up resistor, but could not find any pins to associate with.

We have also tried to get the code working in the functions that have UCTL0 register, then it had some compiling errors, however we have changed all the flag and control registers. I think that our problem is that the code never goes into those functions before.

The CS signal is multiplexed with one of the data pins from parallel mode. (I think it's DAT3)
If during reception of the initial CMD0 this data pin is held low by the master, the SD card will enter serial mode and this pin will act as CS pin until next power cycle. If it is left open (pulled-up by the card), the card will be in parallel mode. You can always switch from parallel to serial mode, but not back again.

Forget what I wrote, I misread the question.

The CD pin (not CS) is not connected to the card. It is a switch on the card slot and operated by the card (closed to GND when the card is inserted and open when there is no card inserted).

Not all card slots implement it. If yours doesn't, you'll have to just try every now and then to init a card that may or may not be there.

Hi again,

Jens-Michael Gross said:

If you want to work with files on the card, you'll need additonal software that provides a file system and uses the SD card sample code for reading and writing the raw data sectors.

#define CSPORT         P3OUT            
#define CLKPORT        P3OUT           
#define DIPORT         P3OUT            
#define DOPORT         P3IN
#define CS              1<<3          
#define CK              1<<0            
#define DI              1<<4            
#define DO_             1<<5           
#define    CS_H()        CSPORT |=  CS    
#define CS_L()        CSPORT &= ~CS    
#define CK_H()        CLKPORT |=  CK    
#define    CK_L()        CLKPORT &= ~CK    
#define DI_H()        DIPORT |=  DI    
#define DI_L()        DIPORT &= ~DI    
#define DO              DOPORT & DO_  

void spi_init (void)
{
  UCA0CTL1 |= UCSWRST;                      // **Put state machine in reset**
  UCA0CTL0 |= UCMST+UCCKPL+UCMSB+UCSYNC;    // 3-pin, 8-bit SPI master
                                            // Clock polarity high, MSB
  UCA0CTL1 |= UCSSEL_2;                     // SMCLK
  UCA0BR0 = 0x02;                           // /2
  UCA0BR1 = 0;                              //
  UCA0MCTL = 0;                             // No modulation
  UCA0CTL1 &= ~UCSWRST;                     // **Initialize USCI state machine**
  UCA0IE |= UCRXIE;                         // Enable USCI_A0 RX interrupt
}

void spi_send_byte(char spi_data)
{
    while(UCTXIFG == 0);
    UCA0TXBUF = spi_data;
}

char spi_get_byte(void)
{
    spi_send_byte(0xff);              
    return spi_data;                
}

Hmmm, I'm nor sure what you've done here.

The defines seem to indicate that it is for a software SPI (No P3SEL defines for switching the SIMO and SOMI and SCl pins to module mode, btu defines for extracting DO and DI from DIPORT and DOPORT)

The two funcitons you defined for sending and receiving a byte through SPI are there, however, spi_get_byte gets - what? It returns spi_data which is undefined in the code you posted and definitely not what the hardware SPI has received.

The wait for (UCTXIFG==0) is void, since UCTXIFG is a non-zero constant. It should be "while(!(UCA0IFG & UCTXIFG));" So you're overwriting TXBUF byte after byte without waiting for the previous byte being sent.

SPI_get_byte, however, should clear UCRXIFG before calling spi_send_byte, then wait for UCRXIFG being set and then return the content of UCA0RXBUF.

One more thing: during initialization, the maximum SPi baudrate for SD cards is 400kHz. Only after initialization, baudrate may be rised to up to 25MHz. But your code seems to start with SMCLK/2 form the beginning, which is most likely way more than 400kHz.
(tip: don't go for maximum speed before it isn't working on lower speed at all.)