SPI share problem

[Bing]

Hi Nordic,

I'm using NRF52832 to design a producation that needs four SPI interfaces.

The four spi peripherals are: gSensor, LCD, SPI Nor Flash, and PPG Sensor. Now I'm planning to make gSensor and LCD share to use SPI0, LCD uses SPI1, and PPG Sensor uses SPI2 repectively.

When design the schematic, each the above peripheral has its own IO pins. So I have to dynmaic switch the pins selection through nrf_drv_spi_uninit() and nrf_drv_spi_init(). 

void spi_share_int(const spi_share_pins_t* spi_hw_info)
{
 if (spi_share_init_flag)
  {
    spi_share_init_flag = 0;
      
    SPI_REG->ENABLE = 0;
    SPI_REG->INTENCLR = 0;
    SPI_REG->INTENSET = 0;
    SPI_REG->PSEL.MISO = 0xFFFFFFFF;
    SPI_REG->PSEL.MOSI = 0xFFFFFFFF;
    SPI_REG->PSEL.SCK = 0xFFFFFFFF;
    SPI_REG->FREQUENCY = 0x04000000;
    SPI_REG->CONFIG = 0;
    SPI_REG->EVENTS_READY = 0;
      
    nrf_drv_spi_uninit(&spi_share);
  }
  
  
  if (spi_share_init_flag == 0)
  {
    spi_share_init_flag = 1;
    
    nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG(SPI_INSTANCE);
    spi_config.frequency = NRF_DRV_SPI_FREQ_500K;
    spi_config.miso_pin = spi_hw_info->miso_pin;
    spi_config.mosi_pin = spi_hw_info->mosi_pin;
    spi_config.sck_pin = spi_hw_info->clk_pin;
    spi_config.ss_pin = 0xFF;
    spi_config.mode = spi_hw_info->mode;
    
    APP_ERROR_CHECK(nrf_drv_spi_init(&spi_share, &spi_config, spi_event_handler));
  }
}

The above spi_share_init() function will be called before each spi communication on SPI0.

But I'm failed, APP_ERROR_CHECK will stop the application run when the program goes to the nrf_drv_spi_init().

Are there some similar usage examples, please kindly help me to solve the probem.

Thanks for any reply.

[ketiljo]

This it not how you should use SPI. It's designed to support multiple slaves. Have a look at this http://www.circuitbasics.com/basics-of-the-spi-communication-protocol/

Use one GPIO as select pin for each slave.

[Bing]

Thanks. I know what is SPI. My problem is I need to reconfig the spi pins(miso, mosi, sck) before a new communication start. When I do this, the nrf_drv_spi_init() return a error code not NRF_SUCCESS. 

[Susheel Nuguru]

what error does it give? does it give NRFX_ERROR_INVALID_STATE? If so, then the uninit was not successful for some reason. I cannot see any other reason for the _init to fail

[Bing]

Sorry, I give the wrong description of my problem. In fact, not the nrf_drv_spi_init() gives the failed error code. But the communication always stops to wait for the current transmission issued by api nrf_drv_spi_transfer() to be complete. It seems that the freuquently uinit and init SPI0 causes the problem. All the SPI0 communications start and done is in the event handler registered by app_sched_event_put(). The using SDK is version 11.0.

[ketiljo]

If you route MISO, MOSI and CLK to both devices and use separate CS (chip select) pins, you don't need to reconfig the SPI pins at all.