Trouble with Zephyr SPI slave

RE: Trouble with Zephyr SPI slave

Jeff4BLE — Mon, 04 Oct 2021 17:46:34 GMT

Additional NCS SPI Reference material Adding a Peripheral to an NCS Zephyr project

Cheers

RE: Trouble with Zephyr SPI slave

Glen M — Mon, 04 Oct 2021 17:21:57 GMT

Well now it's working and I'm not certain what I did to make it so. I did upgrade to the 1.7.0 SDK. Anyway here's the code now in case anyone else is trying to get the nrfx_spis driver going.

//== Includes ================================================================

#include <nrfx.h>
#include <zephyr/types.h>
#include <zephyr.h>
#include <drivers/spi.h>
#include <string.h>
#include "spi_comms.h"
#include <nrfx_spis.h>
#include <logging/log.h>

//== Definitions and Types ===================================================
#define LOG_MODULE_NAME peripheral_SPI
LOG_MODULE_REGISTER(LOG_MODULE_NAME);

#define GPIO_PORT_1_OFFSET 32

#define PIN_SCK            12
#define PIN_MOSI           22
#define PIN_MISO           20
#define PIN_CSN            GPIO_PORT_1_OFFSET + 2

#define SPIS_NR            0     // Using SPI0

#define SPI_BUFFER_SIZE    255

//== Global Variables ========================================================
nrfx_spis_t spi_slave_instance = NRFX_SPIS_INSTANCE(SPIS_NR);

nrfx_spis_config_t spis_config = NRFX_SPIS_DEFAULT_CONFIG(PIN_SCK,PIN_MOSI,PIN_MISO,PIN_CSN);

uint8_t rx_buffer[SPI_BUFFER_SIZE];
uint8_t tx_buffer[SPI_BUFFER_SIZE];

//== Function prototypes =====================================================
void spis_event_handler(nrfx_spis_evt_t const *p_event, void *p_context);

//============================================================================

//----------------------------------------------------------------------------
// Name  : spi_comms_init
// Desc  : Configure the SPI slave device using the nrfx_spis driver
// Ins   : none
// Outs  : none
//----------------------------------------------------------------------------
void spi_comms_init(void)
{
   int err;

   nrf_spis_disable(spi_slave_instance.p_reg);

   err = nrfx_spis_init(&spi_slave_instance, &spis_config, spis_event_handler, NULL);
   if(err != NRFX_SUCCESS)
   {
      LOG_WRN("Error with init.\n");
   } else 
   {
      LOG_WRN("SPIS started.\n");
   }
 
   err = nrfx_spis_buffers_set(&spi_slave_instance, tx_buffer, sizeof(tx_buffer), rx_buffer, sizeof(rx_buffer));
   if(err != NRFX_SUCCESS)
   {
       LOG_WRN("Error with setting.\n");
   }

   IRQ_DIRECT_CONNECT(SPIM0_SPIS0_TWIM0_TWIS0_UARTE0_IRQn, 0, nrfx_spis_0_irq_handler, 0);
   irq_enable(SPIM0_SPIS0_TWIM0_TWIS0_UARTE0_IRQn);
}

//----------------------------------------------------------------------------
// Name  : spis_event_handler
// Desc  : Callback function from the SPI driver
// Ins   : Event pointer and an unused context pointer
// Outs  : none
//----------------------------------------------------------------------------
void spis_event_handler(nrfx_spis_evt_t const *p_event, void *p_context)
{
   int err;
   switch(p_event->evt_type)
   {
      case NRFX_SPIS_XFER_DONE:
         if (p_event->rx_amount > 0)
         {
            LOG_INF("received 0x%02x 0x%02x 0x%02x 0x%02x...\n", rx_buffer[0], rx_buffer[1], rx_buffer[2], rx_buffer[3]);
         }
            
          //LOG_INF("Rx bytes: %u\n", p_event->rx_amount);
          err = nrfx_spis_buffers_set(&spi_slave_instance, tx_buffer, sizeof(tx_buffer), rx_buffer, sizeof(rx_buffer));
          if(err != NRFX_SUCCESS)
          {
             LOG_WRN("Error with setting.\n");
          }
          break;

      case NRFX_SPIS_BUFFERS_SET_DONE:
         //LOG_WRN("buffers set\n");
         break;

      case NRFX_SPIS_EVT_TYPE_MAX:        
         break;
      
      default:
         ;
   }
}

RE: Trouble with Zephyr SPI slave

Sigurd — Mon, 04 Oct 2021 08:22:58 GMT

[quote user="Glen M"]So both this example and the other one I found have the slave actively performing transfers in order to receive things. I was expecting that since my device is a slave that all I had to do was configure the peripheral and then wait for an interrupt to tell me that data had arrived. Is that not the case? Do I have to actively poll for received data?[/quote]

The SPIS handling uses a mutex in the zephyr port "spi_nrfx_spis.c", so even if it looks to be a blocking/polling implementation, it is actually event driven underneath.

[quote user="Glen M"]Is there an appnote or something on how the SPI slave peripheral works? I can't find any real documentation.[/quote]

I'm not aware of any appnote here, but we have the PS: https://infocenter.nordicsemi.com/index.jsp?topic=%2Fps_nrf5340%2Fspis.html

RE: Trouble with Zephyr SPI slave

Glen M — Fri, 01 Oct 2021 23:58:50 GMT

So both this example and the other one I found have the slave actively performing transfers in order to receive things. I was expecting that since my device is a slave that all I had to do was configure the peripheral and then wait for an interrupt to tell me that data had arrived. Is that not the case? Do I have to actively poll for received data?

Also, I found a function called nrf_spis_subscribe_set in the driver. Is that something I need to use? The InfoCenter doesn't tell me anything more about it than what I already guessed from the function name.

Is there an appnote or something on how the SPI slave peripheral works? I can't find any real documentation.

RE: Trouble with Zephyr SPI slave

Glen M — Fri, 01 Oct 2021 18:54:28 GMT

Well I still haven't gotten it working yet but I did solve the problem with the pin assignments. You can't change those once the peripheral is enabled, and I guess it was starting out enabled - so I added a call to nrf_spis_disable before my init call.

RE: Trouble with Zephyr SPI slave

Sigurd — Thu, 30 Sep 2021 14:00:11 GMT

Hi,

A colleague of mine created a SPIS sample some months ago, it might be useful for you to take a look at that sample and see how SPIS is handled there.

Attachment: devzone.nordicsemi.com/.../spis_5F00_thread_5F00_test.rar