SPI (wait for the slave to be ready)

while (P3IN&SOMI); 

can be translated as "if SOMI is high stay in this infinite loop."

I have this feeling that what we try to say here is: if there is no signal at SOMI, that means the slave is ready?

Am I getting this right?

Thank you

Yu,

Conceptually I understand what you are saying, but there are two problems:

1. If you are polling the slave this indicator will not work in true SPI communication unless you use that SOMI pin on the slave side as a GPIO... I think that is what you are trying to do: use that pin as an indicator.

2. The acronym "SOMI" is not defined in the MSP430 headers. I am assuming you are defining that to be a logical high for the MSP430 pin associated with SOMI on the master side.

If the above are taken care of it sounds good to me.

Thank you for your reply Brandon.

You are exactly right. I did not write that code myself, that was from MCU_CC2500 interface code example from TI. The original codes are:

void TI_CC_SPIWriteReg(char addr, char value)
{
    TI_CC_CSn_PxOUT &= ~TI_CC_CSn_PIN;                                                       // /CS enable
    while (TI_CC_SPI_USCIB0_PxIN&TI_CC_SPI_USCIB0_SOMI);                   // Wait for CCxxxx ready
    IFG2 &= ~UCB0RXIFG;                                                                                            // Clear flag
    UCB0TXBUF = addr;                                                                                                // Send address
    while (!(IFG2&UCB0RXIFG));                                                                                 // Wait for TX to finish
    IFG2 &= ~UCB0RXIFG;                                                                                            // Clear flag
    UCB0TXBUF = value;                                                                                               // Send data
    while (!(IFG2&UCB0RXIFG));                                                                                  // Wait for TX to finish
    TI_CC_CSn_PxOUT |= TI_CC_CSn_PIN;                                                           // /CS disable
}

I created my own header and used my own simplified naming conventions. TI_CC_SPI_USCIB0_SOMI happens to be a general purpose Input and Output on CC2500.

Say, what would you do to make sure that the slave is ready?

Thank you

My program hang in

while (TI_CC_SPI_USI_PxIN&TI_CC_SPI_USI_SOMI);// Wait for CCxxxx ready

and SOMI pin is high. Does someboby meet this problem?

void TI_CC_SPIWriteReg(char addr, char value)
{
  TI_CC_CSn_PxOUT &= ~TI_CC_CSn_PIN;        // /CS enable
  while (TI_CC_SPI_USI_PxIN&TI_CC_SPI_USI_SOMI);// Wait for CCxxxx ready
  USISRL = addr;                            // Load address
  USICNT = 8;                               // Send it
  while (!(USICTL1&USIIFG));                // Wait for TX to finish
  USISRL = value;                           // Load value
  USICNT = 8;                               // Send it
  while (!(USICTL1&USIIFG));                // Wait for TX to finish
  TI_CC_CSn_PxOUT |= TI_CC_CSn_PIN;         // /CS disable
}