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TMS320F28388D: SPI communication Receiving 24bit via SPI from slave

aruna revanna
Prodigy 170 points
Part Number: TMS320F28388D

Hi

uint16_t read_data[3] ={0};
uint16_t rData=0;
uint16_t TXRXError=0;
uint32_t sData32=0,rData32 =0;

SPI configuaration as follows

SPI_disableModule(mySPI0_BASE);

SPI_setConfig(mySPI0_BASE, DEVICE_LSPCLK_FREQ, SPI_PROT_POL0PHA0 ,SPI_MODE_MASTER, 1000000, 8);
SPI_enableFIFO(mySPI0_BASE);
SPI_setTxFifoTransmitDelay(mySPI0_BASE,0); 
SPI_disableHighSpeedMode(mySPI0_BASE);
// SPI_enableLoopback(mySPI0_BASE);
SPI_disableLoopback(mySPI0_BASE);
SPI_enableTalk(mySPI0_BASE);
SPI_disableInterrupt(mySPI0_BASE, SPI_INT_TXFF);
SPI_setEmulationMode(mySPI0_BASE, SPI_EMULATION_FREE_RUN);////!Set so breakpoints don't disturb xmission
SPI_enableModule(mySPI0_BASE);

Master can validate data received by slave is correct by validating second response from the slave.

I am transmitting same 24-bit data twice to the slave to get  response of 24 bits from slave. I am comparing first 24bits transmitted with 2nd time received 24bits of the data.but I am not getting correct data.

I am missing something while receiving data.

SPI_transmit24Bits(mySPI0_BASE, sData32, 0);
SPI_transmit24Bits(mySPI0_BASE, sData32, 0);
read_data[0] = SPI_readRxEmulationBuffer(mySPI0_BASE);
read_data[1] = SPI_readRxEmulationBuffer(mySPI0_BASE);
read_data[2] = SPI_readRxEmulationBuffer(mySPI0_BASE);

rData = read_data[1] << 8 ;
rData = rData | read_data[2];

Thanks in advance

  • 0
    TI__Mastermind 21926 points

    Hi Aruna,

    Our subject matter expert is currently out of office and will get back to you the following business day.

    Best regards,

    Ryan Ma

  • 0 in reply to Ryan Ma
    TI__Guru 55700 points

    If you're trying to receive 24 bits from target (slave), why are you using SPI_transmit24Bits function?

    Are you trying to transmit contents of sData32 variable?

    Did you already look into readData function in spi_ex6_eeprom example?

    Regards,

    Manoj

  • 0 in reply to Manoj Santha Mohan
    Prodigy 170 points

    If you're trying to receive 24 bits from target (slave), why are you using SPI_transmit24Bits function?

    Ans: I would like to transmit 24bits data to slave and same time I would like to receive 24bit response from the slave. so I am using SPI_transmit24Bits function to transmit the data.

    Are you trying to transmit contents of sData32 variable?

    Ans:Yes.Here also I have one question, will Left justified 24bit data will get transmitted or right justified 24bits get transmit?

    Did you already look into readData function in spi_ex6_eeprom example?

    No.

    I have one more question when to use FIFO enabled SPI or when not to use?

    Thanks in advance

  • 0 in reply to aruna revanna
    TI__Guru 55700 points

    Aruna,

    For transmit and receiving at the same time you can use the below function

    For sending / receiving 24 bits, you need to set charLength = 8, numofWords = 3 (8 bits x 3 = 24 bits)

    aruna revanna said:
    I have one more question when to use FIFO enabled SPI or when not to use?

    Typically, FIFO are added to reduce the frequency at which SPI generates CPU interrupt. If you are using polling option, then you don't need to worry about it.

    Regards,

    Manoj