S32K中的主题 Re: Why is CS pulled high before LPSPI has finished transmitting?

Why is CS pulled high before LPSPI has finished transmitting?

kalvin — Mon, 19 Sep 2022 07:53:09 GMT

void SPI_Init(LPSPI_Type *instance,SpiSpeedType Speed)
{
instance->IER = 0x00000000; /* Interrupts not used */
instance->DER = 0x00000000; /* DMA not used */
instance->CFGR0 = 0x00000000; /* Defaults: */
/* RDM0=0: rec'd data to FIFO as normal */
/* CIRFIFO=0; Circular FIFO is disabled */
/* HRSEL, HRPOL, HREN=0: Host request disabled */
instance->CFGR1 = LPSPI_CFGR1_MASTER(1); /* Configurations: master mode */
/* PCSCFG=0: PCS[3:2] are enabled */
/* OUTCFG=0: Output data retains last value when CS negated */
/* PINCFG=0: SIN is input, SOUT is output */
/* MATCFG=0: Match disabled */
/* PCSPOL=0: PCS is active low */
/* NOSTALL=0: Stall if Tx FIFO empty or Rx FIFO full */
/* AUTOPCS=0: does not apply for master mode */
/* SAMPLE=0: input data sampled on SCK edge */
/* MASTER=1: Master mode */

instance->TCR |= LPSPI_TCR_PRESCALE(SpiSpeed.prescale)| /* PRESCALE=2: Functional clock divided by 40M/2 = 20M */
LPSPI_TCR_PCS(2) |
LPSPI_TCR_FRAMESZ(7); /* FRAMESZ=7: # bits in frame = 7+1=8 */

instance->CCR |= LPSPI_CCR_SCKDIV(SpiSpeed.sckdiv) | /* 20/(8+2) = 2M */
LPSPI_CCR_DBT(8) |
LPSPI_CCR_SCKPCS(4) |
LPSPI_CCR_PCSSCK(4);

instance->FCR = LPSPI_FCR_TXWATER(3); /* RXWATER=0: Rx flags set when Rx FIFO >0 */
/* TXWATER=3: Tx flags set when Tx FIFO <= 3 */
instance->CR = LPSPI_CR_MEN_MASK
|LPSPI_CR_DBGEN_MASK; /* Enable module for operation */
/* DBGEN=1: module enabled in debug mode */
/* DOZEN=0: module enabled in Doze mode */
/* RST=0: Master logic not reset */
/* MEN=1: Module is enabled */
}
uint8_t LPSPI_ReadWriteByte(LPSPI_Type *instance,uint8_t byte)
{
uint8_t recieve = 0;

while((instance->SR & LPSPI_SR_TDF_MASK)>>LPSPI_SR_TDF_SHIFT==0);
/* Wait for Tx FIFO available */
instance->TDR = byte; /* Transmit data */
instance->SR |= LPSPI_SR_TDF_MASK; /* Clear TDF flag */

while((instance->SR & LPSPI_SR_RDF_MASK)>>LPSPI_SR_RDF_SHIFT==0);
/* Wait at least one RxFIFO entry */
recieve= instance->RDR; /* Read received data */
instance->SR |= LPSPI_SR_RDF_MASK; /* Clear RDF flag */

return recieve; /* Return received data */
}

Re: Why is CS pulled high before LPSPI has finished transmitting?

davidtosenovjan — Tue, 20 Sep 2022 11:53:06 GMT

It is given by following bits in Transmit Command Register (TCR):

Re: Why is CS pulled high before LPSPI has finished transmitting?

kalvin — Tue, 20 Sep 2022 12:18:58 GMT

@davidtosenovjan thanks for your answer,but why there are three bytes before each byte is 0x00, please see the picture in the attachment .

Re: Why is CS pulled high before LPSPI has finished transmitting?

davidtosenovjan — Wed, 21 Sep 2022 12:32:43 GMT

Why you are transmitting per four bytes when the function seems to be written per byte? Which data you are transmitting, it is not apparent from your code snippet.

Re: Why is CS pulled high before LPSPI has finished transmitting?

kalvin — Wed, 21 Sep 2022 13:00:30 GMT

transmit buffer is ：

spi_buffer_t master_buffer =
{
.tx = {0xA,0xB,0xC,0xD,0xE,0xF,0x9,0x8,0x7,0x6,0x5,0x4,0x3,0x2,0x1,0xAA},
.rx = {0}
};

Re: Why is CS pulled high before LPSPI has finished transmitting?

kalvin — Wed, 21 Sep 2022 13:05:04 GMT

Re: Why is CS pulled high before LPSPI has finished transmitting?

kalvin — Fri, 23 Sep 2022 01:18:23 GMT

@davidtosenovjan The null byte problem has been solved, but I still have a question to ask, why does CS keep low level after TCD CONC is enabled? Please see the attached picture .

Re: Why is CS pulled high before LPSPI has finished transmitting?

davidtosenovjan — Fri, 23 Sep 2022 12:31:17 GMT

Here you may read description to understand how to set CONT/CONTC bits:

https://community.nxp.com/t5/S32K/S32K14x-Command-Word-in-LPSPI/td-p/1040779

Re: Why is CS pulled high before LPSPI has finished transmitting?

kalvin — Mon, 26 Sep 2022 09:17:38 GMT

Thanks @davidtosenovjan my problem has been solved ！