SPI clock resting on logic high when CPOL=0

[denjos007]

Hi,

I have an SPI setup in the FLEXCOMM8 of LPC55s69 board. Its setup to be CPOL=0 and CPHA=0. I would expect the SCLK to return to 0 after each packet. However when scoping this, the observed behaviour is the opposite.

Is there a something that I can change to reverse this behaviour, as the chip i am interfacing with is getting erroneous data

Thanks

[denjos007]

Hi Alice,

I am not using the MCUXpressoIDE, instead, I am using CLion, and in that case, I am not able to view the registers using PyOCD. I had raised a community post on it and was basically asked to use the MCUXpressoIDE. So i can not confirm it using register view, however using the confid tools, i am setting the CPOL to 0 and seeing the same in pheripherals.c

const spi_master_config_t FLEXCOMM8_config = {
  .enableLoopback = false,
  .enableMaster = true,
  .polarity = kSPI_ClockPolarityActiveHigh,
  .phase = kSPI_ClockPhaseFirstEdge,
  .direction = kSPI_MsbFirst,
  .baudRate_Bps = 1000000UL,
  .dataWidth = kSPI_Data8Bits,
  .sselNum = kSPI_Ssel0,
  .sselPol = kSPI_SpolActiveAllLow,
  .txWatermark = kSPI_TxFifo0,
  .rxWatermark = kSPI_RxFifo1,
  .delayConfig = {
    .preDelay = 0U,
    .postDelay = 0U,
    .frameDelay = 0U,
    .transferDelay = 0U
  }
};

static void FLEXCOMM8_init(void) {
  /* Initialization function */
  SPI_MasterInit(FLEXCOMM8_PERIPHERAL, &FLEXCOMM8_config, FLEXCOMM8_CLOCK_SOURCE);
}

I had used a sample program similar to the SPI example and found the same behaviour

Now if i change the CPOL to 1, the behavior is as required. SPI clock and MOSI outputs default to low. This means that i cannot use CPOL=0 for interfacing with the system I am using. Is there any way to reverse this behaviour for CPOL=0?

Regards,

Joseph

[Alice_Yang]

Hello,

I use the SDK demo "lpcxpresso55s69_spi_interrupt_b2b_transfer_master"test the on my side, there is no problem.

BR

Alice

[Alice_Yang]

Hello ,

Could you please confirm  SPI configuration register set CPOL to 0 correctly, can using IDE register view.

And how about use the SPI example under SDK to test. 

BR

Alice