SPI with several chip selects

[matthias]

Hello everyone,

I am using KSDK 1.1.0 on a FRDM-K64 board and would like to use an SPI port with multiple chip selects (multiple connected slaves). I used Processor Expert to set up the DSPI peripheral with two different master configurations that have their dedicated chip select pin.

My question is: How can I change between using the two chip selects? I would like to avoid to reinitialize the whole driver by using DSPI_DRV_Master(De)Init() each time. Is there any simple way to switch between several chip selects?

Best regards

Matthias

[Alice_Yang]

Hi matthias ,

You can use "DSPI_HAL_StartTransfer()"  and "DSPI_HAL_StopTransfer()" change between using the two chip selects.

Best Regards,
Alice

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[oaf]

Are you sure? According to the comment in peripeherals_init.c:

/*!

* @brief Starts the DSPI transfers, clears HALT bit in MCR.

*

* This function call called whenever the module is ready to begin data transfers in either master

* or slave mode.

*

* @param baseAddr Module base address

*/

static inline void DSPI_HAL_StartTransfer(uint32_t baseAddr)

{

    BW_SPI_MCR_HALT(baseAddr, 0);

}

How does this sw change the PCS bits in the SPIx_PUSHR register?

[Alice_Yang]

HI Ole

(1) At the begin of the project , it need initialize both SPI0 and SPI1,

complete the two component  basic SPI configure.

And   delete "

  /* Start the transfer process in the hardware */

    DSPI_HAL_StartTransfer(baseAddr);

"

(2)  n the process of replacement , use the function   "DSPI_HAL_StartTransfer()"  and "DSPI_HAL_StopTransfer()".

(3) About the bit PCS[x] you said , both PCS[0] and PCS[1] (if use SPI0 and SPI1 ) already set "Assert"  in the initialize function.

(4) Of course ,  if there have public register the two SPI  both use ,and only can select one SPI in this register ,  it need reconfigure in the change period.

BR

Alice

[matthias]

Hello Alice,

thanks for your reply. I think there is a misunderstanding. I do not want to use two different SPI ports. As said, I have two slaves connected to the same SPI port (in my case SPI0) and I want to change the chip select that is used when transferring data.

I figured out that the PCS bits in the SPI0_PUSHR register should be changed as Ole said. To achieve this, I change the component whichPcs in the structure g_dspiStatePtr[FSL_SPICOM0] that is used globally in fsl_dspi_master_driver.c. Like this, the correct PCS bits are set when calling  DSPI_DRV_MasterTransferBlocking(), for example.

Is this the right way to do it or are there any functions in the KSDK driver that should be used?

Best regards,

Matthias

[Alice_Yang]

Hi mattias,

I know your meaning .

In the KSDK, there is not the driver function to change slave spi.

I recommend you configure the pcs pin  to  GPIO pin,  when want to select the slave spi, set the related pin to 0, the other on to 1.

BR

Alice