SPI configuration for nrf52832

[Marc]

I've configured the SPI with DMA module as in the code below.

I've loaded the tx buffer with sample data and start the transaction; however, I'm not reading anything either on the MOSI pin or the MISO pin. The SCK pin also stays low. The tx and rx end events do go from 0 to 1 correctly.

Any ideas what I'm doing wrong?

Thanksspi code.rtf

[hmolesworth]

This your code correctly working on an SPI accelerometer; the delays are arbitrary and not tested with other values (just there to mimic your delays). The returned value is correct:

#define CSPIN   ACC_CS_PIN   // 11  //spi chip select
#define SCKPIN  ACC_SCK_PIN  // 12  //spi clock
#define MOSIPIN ACC_MOSI_PIN // 13  //spi mosi
#define MISOPIN ACC_MISO_PIN // 14  //spi miso

#define LIS2DH12_WHO_AM_I          0x0F                          // Read as 0x33

uint8_t spiTXBuf[] = {0x80|LIS2DH12_WHO_AM_I, 0xFF};
uint8_t spiRXBuf[sizeof(spiTXBuf)];
static const uint8_t mRxTxBufLength = sizeof(spiTXBuf);

void TestSPI(void)
{
  NRF_GPIO->PIN_CNF[CSPIN] = 1;  //output
  NRF_GPIO->PIN_CNF[SCKPIN] = 1;  //output
  NRF_GPIO->PIN_CNF[MOSIPIN] = 1;  //output
  NRF_GPIO->PIN_CNF[MISOPIN] = 0;  //input pin, input buffer connected, no pull, S0S1, sense disabled
  NRF_GPIO->OUTSET = 1 << CSPIN;  //deactivate by setting chip select high
  NRF_SPIM0->PSEL.SCK = SCKPIN;
  NRF_SPIM0->PSEL.MOSI = MOSIPIN;
  NRF_SPIM0->PSEL.MISO = MISOPIN;
  NRF_SPIM0->CONFIG = 0; //2; // 0b010;  //CPOL 0 -- clock polarity active high, CPHA 1 -- sample on trailing clock edge, send Msb first
  NRF_SPIM0->FREQUENCY = 0x20000000;  //2 Mbps
//uint8_t spiTXBuf[2];  //2 byte tx buffer
//uint8_t spiRXBuf[2];  //2 byte rx buffer
//spiTXBuf[0] = ADS_CMND_RREG; // 0b10101010;  //example byte
//spiTXBuf[1] = 2-1; // 0b10101010;  //example byte

  nrf_delay_us(200);                  // Delay to allow 18 tclk minimum
  NRF_SPIM0->ENABLE = 7;  //enabled

  NRF_SPIM0->TXD.PTR = (uint32_t)((uint8_t *)spiTXBuf);
  NRF_SPIM0->TXD.MAXCNT = mRxTxBufLength; //2;
  NRF_SPIM0->RXD.PTR = (uint32_t)((uint8_t *)spiRXBuf);
  NRF_SPIM0->RXD.MAXCNT = mRxTxBufLength; //2;
//  NRF_SPIM0->ENABLE = 7;  //enabled
  NRF_SPIM0->EVENTS_ENDTX = 0;
  NRF_SPIM0->EVENTS_ENDRX = 0;
  NRF_GPIO->OUTCLR = 1 << CSPIN;  //drive cs low to initiate spi comm
//for(uint8_t i = 0; i < 21; i++) __asm__("nop\n\t");  //low for 21 machine instructions
  nrf_delay_us(200);
  NRF_SPIM0->TASKS_START = 1;
  while(!NRF_SPIM0->EVENTS_ENDTX);  //last byte transmitted
  while(!NRF_SPIM0->EVENTS_ENDRX);  //last byte received
  NRF_SPIM0->TASKS_STOP = 1;
  NRF_GPIO->OUTSET = 1 << CSPIN;
  while(1);
}