I have a NRF52840 Dev Kit and a ESP32-S3 Dev kit, I want to do a SPI communication between them. Here NRF works as SPI Master and ESP works as SPI Slave. I am using SDK-17.1 for development. For SPI Master code I have taken an example code and used the same pins which are given in that code. My work flow is to send a 32 Bytes of data from Master to Slave then Slave will respond on that . So as per the SPI I need to send two commands from Master to read the data from Slave. In first command '0x11', Slave will prepare the data on its side, then Master will send a dummy command '0x13' to read that data.
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#include "nrf_drv_spi.h"
#include "app_util_platform.h"
#include "nrf_gpio.h"
#include "nrf_delay.h"
#include "boards.h"
#include "app_error.h"
#include <string.h>
#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"
#define SPI_INSTANCE 0 /**< SPI instance index. */
static const nrf_drv_spi_t spi = NRF_DRV_SPI_INSTANCE(SPI_INSTANCE); /**< SPI instance. */
static volatile bool spi_xfer_done; /**< Flag used to indicate that SPI instance completed the transfer. */
//uint8_t
#define BUFFER_SIZE 32
static uint8_t m_tx_buf[BUFFER_SIZE] ={0};
static uint8_t m_rx_buf[BUFFER_SIZE]; /**< RX buffer. */
static const uint8_t m_length = sizeof(m_tx_buf); /**< Transfer length. */
/**
* @brief SPI user event handler.
* @param event
*/
void spi_event_handler(nrf_drv_spi_evt_t const * p_event,
void * p_context)
{
spi_xfer_done = true;
NRF_LOG_INFO("Transfer completed.");
// if (m_rx_buf[0] != 0) // Check received data in SPI Rx buffer
{
NRF_LOG_INFO(" Received:");
NRF_LOG_HEXDUMP_INFO(m_rx_buf, sizeof(m_rx_buf));
}
}
bool toggle = 1;
int main(void)
{
bsp_board_init(BSP_INIT_LEDS);
APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
NRF_LOG_DEFAULT_BACKENDS_INIT();
nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG;
/* Note: 1, When you are controlling chip select by application firmware, it require to init chip select pin as NOT_USED while init spi driver. Else SPI driver will also control the same pin while communicating on SPI. */
spi_config.ss_pin = NRFX_SPIM_PIN_NOT_USED; // SPI_SS_PIN;//31
spi_config.miso_pin = SPI_MISO_PIN;//30
spi_config.mosi_pin = SPI_MOSI_PIN;//29
spi_config.sck_pin = SPI_SCK_PIN;//26
spi_config.frequency = NRF_DRV_SPI_FREQ_4M;
APP_ERROR_CHECK(nrf_drv_spi_init(&spi, &spi_config, NULL, NULL));
nrf_gpio_cfg_output(SPI_SS_PIN);
nrf_gpio_pin_set(SPI_SS_PIN);
NRF_LOG_INFO("SPI example started.");
while (1)
{
// Reset rx buffer and transfer done flag
memset(m_rx_buf, 0, m_length);
if(toggle == 1){
m_tx_buf[0] = 0x11;
m_tx_buf[1] = 0xfa;
m_tx_buf[2] = 0xfb;
for(uint8_t i =3;i<BUFFER_SIZE;i++){
m_tx_buf[i] = i;
}
nrf_gpio_pin_clear(SPI_SS_PIN);
APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, m_tx_buf,1, NULL, 0));
nrf_gpio_pin_set(SPI_SS_PIN);
}
else{
m_tx_buf[0] = 0x13;
for(uint8_t i =1;i<BUFFER_SIZE;i++){
m_tx_buf[i] = 0;
}
nrf_gpio_pin_clear(SPI_SS_PIN);
APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, m_tx_buf, 1, NULL, 0));
APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, NULL, 0, m_rx_buf, BUFFER_SIZE));
nrf_gpio_pin_set(SPI_SS_PIN);
}
toggle = ! toggle;
nrf_delay_ms(200);
}
}
This is my main.c file for SPI master code.
Here I have uploaded the SPI slave code also, SPI slave code is working fine , I have tested it by communicating between two ESP32 as Master and Slave. I am facing issue in communication between ESP32-S3 and NRF 52840 only
While communication I am facing following issues
- When we send a single byte of data from SPI master and does not send ,or put zero in TX buffer of Slave - Then Slave receives correct data which is send by Master
- In above case Master does not receives any data.
- In other case When we send a single byte of data from SPI master and if we put non zero values in TX buffer of Slave - Then Slave receives incorrect data or garbage
- In above case also master does not receive any data
- When we send 32 Bytes of data from Master and put non zero values in TX buffer of slave - Then Master receives garbage values and Slave also receives garbage values
When NRF sending single byte and ESP send no data then
| ESP side | NRF side |
 |
 |
When ESP send 0x01 , Here we can see that ESP side Rx buff receives an extra byte 80 even which is not send from Master side
 |
 |
When ESP send 0x01 and NRF send 32 Bytes of data , then ESP RX buffer receives all garbage after that but in this case Master receives a single bytes which is send by Slave
 |
 |
In all above cases when, I disconnect the MISO line from Master side Slave side , then Slave receives all 32 bytes correctly , but as MISO line is disconnected so Master does not receives any data.
My observation is, something is interfering with MISO line data . Even I have tested with different clock frequency also but nothing helps out. What would be the possible cause of issue and what I am doing wrong in this communication ?Please help me with that.
