Hi, I am trying to figure out why my SPI timing diagram looks like below:
As you can see, the clocks don't look proper and there are not even enough of them.
Here is my SPI config code for EUSCI_B0:
static const eUSCI_SPI_MasterConfig SD_SPI_Config =
{
EUSCI_B_SPI_CLOCKSOURCE_SMCLK,
3000000, //Source clk (SMCLK) speed
200000, //Desired SPI clk spd
EUSCI_SPI_MSB_FIRST,
EUSCI_SPI_PHASE_DATA_CAPTURED_ONFIRST_CHANGED_ON_NEXT,
EUSCI_SPI_CLOCKPOLARITY_INACTIVITY_LOW,
EUSCI_SPI_3PIN
};
static void power_on (void)
{
UCB0CTLW0 |= BIT0; //UCSWRST = 1 //SPI_disableModule()?
/* Configure MOSI/MISO/SCLK/CS pins */
/*
* eUSCI B0:
*
* OUT - MOSI: P1.6
* IN - MISO: P1.7
* OUT - SCLK: P1.5
* OUT - CS : P4.6
* IN - CD : P4.7
*/
P4->OUT |= BIT6; //Set CS default value to high
P4->DIR |= BIT6; //Set CS as output
//P4->DIR &= ~BIT7; //Set CD (card detect) as input
P1SEL1 &= (~BIT7 & ~BIT6 & ~BIT5);
P1SEL0 |= BIT7 | BIT6 | BIT5; //Set SPI pins to use primary function instead of GPIO
//debug: add pullup resistor to MISO
//P1->OUT |= BIT7;
//P1->REN |= BIT7;
SPI_initMaster(EUSCI_B0_BASE, &SD_SPI_Config); //Set eUSCI B0 SPI registers
UCB0CTLW0 &= ~BIT0; //UCSWRST = 0 //SPI_enableModule()?
}
And here is my SPI transfer function:
/* Exchange a byte */
static
BYTE xchg_spi ( /* Returns received data */
BYTE dat /* Data to be sent */
)
{
SPI_transmitData(EUSCI_B0_BASE, dat);
while(!EUSCI_B_SPI_getInterruptStatus(EUSCI_B0_BASE, EUSCI_B_SPI_RECEIVE_INTERRUPT));
//while(EUSCI_B_SPI_isBusy(EUSCI_B0_BASE));
return EUSCI_B_SPI_receiveData(EUSCI_B0_BASE);
}
And lastly, here is my driver code:
power_on();
while(1){
CS_LOW(); //Chip select goes low
xchg_spi(0xAA);
CS_HIGH(); //Chip select goes high
}
Also for background, while I don't think this should matter, I am trying to initialize/communicate with a MMC card in SPI mode. I am trying first to ensure that I am using SPI correctly.
Any ideas for what could be going wrong?
