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Troubleshooting with SPI0 using MK10

Question asked by Michael K on Jul 11, 2016
Latest reply on Jul 12, 2016 by Hui_Ma



at the moment I'm facing a problem with SPI0. I want to establish a connection to a pressure sensor at this interface. The clock initialization looks like:

  SIM_SCGC5 = 0x00

            | SIM_SCGC5_PORTE_MASK

            | SIM_SCGC5_PORTD_MASK                                                       

            | SIM_SCGC5_PORTC_MASK                                                               

            | SIM_SCGC5_PORTB_MASK                                                       

            | SIM_SCGC5_PORTA_MASK;    


  SIM_SCGC6 = 0x00

            | SIM_SCGC6_PIT_MASK

            | SIM_SCGC6_SPI0_MASK;  


After that, I initialized the SPI module, using the following code:

/* Function to initialize the SPI 0 interface at a frequency of 2.4MHz */

void init_spi_0(void)


  /* Use alternative 2 on pin 0 of PORTD (CS) */

  PORTD_PCR0 = 0x00

             | PORT_PCR_MUX(0x02);


  /* Use alternative 2 on pin 1 of PORTD (CLK) */

  PORTD_PCR1 = 0x00

             | PORT_PCR_MUX(0x02);


  /* Use alternative 2 on pin 2 of PORTD (MOSI) */

  PORTD_PCR2 = 0x00

             | PORT_PCR_MUX(0x02);   


  /* Use alternative 2 on pin 3 of PORTD (MISO) */

  PORTD_PCR3 = 0x00

             | PORT_PCR_MUX(0x02)

             | PORT_PCR_PE_MASK

             | PORT_PCR_PS_MASK; 


  /* Use SPI0 as master, CS0 is low-active, clear TX FIFO and clear RX FIFO */

  SPI0_MCR = 0x00

           | SPI_MCR_MSTR_MASK

           | SPI_MCR_PCSIS(0x01)

           | SPI_MCR_DIS_TXF_MASK

           | SPI_MCR_DIS_RXF_MASK;


  /* Use in every frame 8 bits (0x08), baud rate prescaler is 3 (0x01) and the

  baud rate scaler is 2 (0x00) creating a SPI frequency of 8.33MHz */

  SPI0_CTAR0 = 0x00

             | SPI_CTAR_FMSZ(0x08)

             | SPI_CTAR_CPOL_MASK

             | SPI_CTAR_PBR(0x1)

             | SPI_CTAR_BR(0x00); 



To write or read data I use the code:

/* Function to send or read a byte */

uint8_t write_read_spi_0(int8_t data, uint32_t continuous)


  switch (continuous){

      case 0:

        /* Use a continuous chip select, assert PCS0 and write the byte to the register */

        SPI0_PUSHR = 0x00

                   | SPI_PUSHR_CONT_MASK

                   | SPI_PUSHR_CTAS(0x00)

                   | SPI_PUSHR_PCS(0x01)

                   | SPI_PUSHR_TXDATA(data);                



      case 1:

        /* Assert PCS0 and write the byte to the register */

        SPI0_PUSHR = 0x00

                   | SPI_PUSHR_CTAS(0x00)

                   | SPI_PUSHR_PCS(0x01)

                   | SPI_PUSHR_TXDATA(data);        




  /* Wait for the byte to be sent */

  while(!(SPI0_SR & SPI_SR_TCF_MASK));


  /* Read the received byte */

  data = SPI0_POPR;  


  /* Clear the flag (not self-clearing) */



  /* Return value */

  return (data);



I checked the signals with a scope and the signal CLK and MOSI are as expected. Only MISO remains low all the time.


The next step I made was connecting MISO to the power supply. If I use MISO as a GPIO I'm able to read in the right logic levels. If I switch back to SPI the results are wrong again. I recognized that 0x01FF is shifted through registers SPI0_RXFR0 till SPI0_RXFR3 (I need four write/read cyles) and if it reached register SPI0_RXFR3 it is written into SPI0_POPR.


Does anyone know what I'm doing wrong? I thought I had switched of the FIFO registers.


Thank you for your help.