KW38's CS cannot be controlled through gpio.

[tedwu1]

Hello friend,

I want to use gpio as CS because I have 3 SPI devices. I use frdmkw38_dspi_polling_b2b_transfer_master project. But the CS (PTA19) pin always high. I cannot control it to low. I modified some code as follows. Can anyone guide me? Thank you in advance.

Best wishes

Ted Wu

pin_mux.c
void BOARD_InitPins(void)
{
...
/* PORTA16 (pin 4) is configured as SPI1_SOUT */
PORT_SetPinMux(PORTA, 16U, kPORT_MuxAlt2);

/* PORTA17 (pin 5) is configured as SPI1_SIN */
PORT_SetPinMux(PORTA, 17U, kPORT_MuxAlt2);

/* PORTA18 (pin 6) is configured as SPI1_SCK */
PORT_SetPinMux(PORTA, 18U, kPORT_MuxAlt2);

/* PORTA19 (pin 7) is configured as SPI1_PCS0 */
PORT_SetPinMux(PORTA, 19U, kPORT_MuxAsGpio);

PORTA->PCR[19] = ((PORTA->PCR[19] &
/* Mask bits to zero which are setting */
(~(PORT_PCR_SRE_MASK | PORT_PCR_ISF_MASK)))

/* Slew Rate Enable: Fast slew rate is configured on the corresponding pin, if the pin is
* configured as a digital output. */
| PORT_PCR_SRE(kPORT_FastSlewRate));
....
}

dspi_polling_b2b_transfer_master.c
int main(void)
{
BOARD_InitPins();
BOARD_BootClockRUN();
BOARD_InitDebugConsole();

/* Define the init structure for the output pin */
gpio_pin_config_t gpio_1_config = {
kGPIO_DigitalOutput,
1,
};
...
srcClock_Hz = DSPI_MASTER_CLK_FREQ;
DSPI_MasterInit(EXAMPLE_DSPI_MASTER_BASEADDR, &masterConfig, srcClock_Hz);

/* Init output CS GPIO. */
GPIO_PinInit(GPIOA, 19U, &gpio_1_config);

while (1)
{
...
/* Start master transfer, send data to slave */
masterXfer.txData = masterTxData;
masterXfer.rxData = NULL;
masterXfer.dataSize = TRANSFER_SIZE;
masterXfer.configFlags = kDSPI_MasterCtar0;
GPIO_PinWrite(GPIOA, 1U << 19, 0);
DSPI_MasterTransferBlocking(EXAMPLE_DSPI_MASTER_BASEADDR, &masterXfer);
GPIO_PinWrite(GPIOA, 1U << 19, 1);
...
}

[tedwu1]

Hi @EduardoZamora 

If I use a single SPI, I can control the PTA19 (CS) potential level through the SPI program. But I have 3 SPI devices. I want to use gpio as CS (chip select) to distinguish which SPI is used at a time. So I want to use gpio as CS. But if I use gpio as CS I can't control it.

Best wishes

Ted Wu

[EduardoZamora · Accepted solution]

Hi,

Just as a quick test you can try the following:

In pin_mux.c > BOARD_InitPins(), add 

PORT_SetPinMux(PORTC, 3U, kPORT_MuxAsGpio);

In dspi_transfer_master.c, add the following after pins and clock initialization:

gpio_pin_config_t gpio_as_cs = {
    kGPIO_DigitalOutput,
    1,
};

GPIO_PinInit(GPIOC, 3U, &gpio_as_cs);

After that, try writing the GPIO output:

GPIO_PinWrite(GPIOC, 3U, 0);
/* Delay */
for (i = 0U; i < EXAMPLE_DSPI_DEALY_COUNT; i++)
 {
 __NOP();
 }
 GPIO_PinWrite(GPIOC, 3U, 1);

You should see that the GPIO output level changes. However, please consider taking a look at the FRDM-KW38 schematics file to confirm that the pin you are trying to configure is not being used or connected to another module.

Please, let me know your findings.

Regards,
Eduardo.

[tedwu1]

Hi @EduardoZamora 

Thank you very much.

Ted Wu

[EduardoZamora]

Hello @tedwu1

Hope you are doing well.

According to the FRDM-KW38 schematics (which can be downloaded from the FRDM-KW38 webpage, Design Files section), PTA19 should be connected to FXOS8700CQ Combo Sensor Pin 11 (INT1). Please, consider using another pin as GPIO for your application.

Regards,
Eduardo.