topic Re: SPI with several chip selects in Kinetis Software Development Kit

SPI with several chip selects

matthias — Fri, 23 Jan 2015 14:07:02 GMT

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

Re: SPI with several chip selects

Alice_Yang — Mon, 26 Jan 2015 02:12:03 GMT

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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Re: SPI with several chip selects

oaf — Mon, 26 Jan 2015 07:30:35 GMT

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?

Re: SPI with several chip selects

Alice_Yang — Mon, 26 Jan 2015 08:24:21 GMT

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.

Alice

Re: SPI with several chip selects

matthias — Mon, 26 Jan 2015 09:21:46 GMT

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

Re: SPI with several chip selects

Alice_Yang — Mon, 26 Jan 2015 12:10:00 GMT

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.

Alice