FLEXIO as SPI configuration

[gschelotto]

Hi,

I'm evaluating FLEXIO as SPI using SDK v3.2.1 on a FRDM-KL27Z. Basically I'd need to solve 2 things:

• Set the CLK Polarity Active Low, not High as provided in the frdmkl27z_driver_examples_flexio_flexio_spi_int_spi_transfer_master
• Disable CS assertion by the driver. I need to set/clear the CS manually. Similar way than the output mode configuration (kSPI_SlaveSelectAsGpio) in the SPI driver.

How can I do to accomplish these points?

regards,

gaston

[HeMyFAE]

HI Gerardo,

Can you check with the SDK team on whether we have implemented FlexIO SPI driver with the ability to invert the clock polarity for i.xm RT 10xx?

Regards,

hy

[gerardo_rodriguez]

Hello Gaston,

The FlexIO SPI driver doesn't support CPOL=1 (idle high), but as mentioned in the KL27P64M48SF2RM, you can manually change the pin polarity of the timer used for SCK generation to support this:

In FLEXIO_SPI_MasterInit(): 

    /*3. Configure the timer 0 for SCK. */
    timerConfig.triggerSelect = FLEXIO_TIMER_TRIGGER_SEL_SHIFTnSTAT(base->shifterIndex[0]);
    timerConfig.triggerPolarity = kFLEXIO_TimerTriggerPolarityActiveLow;
    timerConfig.triggerSource = kFLEXIO_TimerTriggerSourceInternal;
    timerConfig.pinConfig = kFLEXIO_PinConfigOutput;
    timerConfig.pinSelect = base->SCKPinIndex;
//    timerConfig.pinPolarity = kFLEXIO_PinActiveHigh;
    timerConfig.pinPolarity = kFLEXIO_PinActiveLow;‍‍‍‍‍‍‍‍

About the CS pin, you can manually change the pin muxing to GPIO instead of the FlexIO so you can manually control it. 

Regards,

Gerardo

[gschelotto]

Hi Gerardo,

Thanks for replying. I assume I have to modify the FlexIO SPI driver in order to change the pin polarity of the timer. Will this feature be implemented in the next SDK version?

regards,

gaston

[gerardo_rodriguez · Accepted solution]

Hi Gaston,

Yes, the FlexIO SPI driver must be modified to invert the clock polarity.

Unfortunately, I don't know if this feature will be implemented in future versions of the SDK.

Regards,

[gschelotto]

Please could someone give me some feedback? I thought I could use an extra SPI interface without constraints but I don't know how to do it.

https://community.nxp.com/thread/471557 

regards,

gaston