RE: Send more than 256 bytes using nrf_drv_spi_transfer() in nRF52832 by manually control the SS pin

jinvers — Tue, 14 Mar 2023 14:22:42 GMT

Ok. Thank you.

Regards,

Joel

RE: Send more than 256 bytes using nrf_drv_spi_transfer() in nRF52832 by manually control the SS pin

Jørgen Holmefjord — Tue, 14 Mar 2023 12:54:08 GMT

Hi,

[quote user=""]I have seen from the code of the nrfx_spim_xfer() function (called into the nrf_drv_spi_transfer function) I can only select the option NRFX_SPIM_PIN_NOT_USED of using ALL the SPI pins in this function or noone.[/quote]

I'm not sure if I understand what you mean here. The pins are set when you initialize the driver (nrfx_spim_init()), where you can set each individual pin to either the pin number or to NRFX_SPIM_PIN_NOT_USED. The SS pin is controlled by software in the driver for all SPI instances in nRF52832, but if you set the pin to NRFX_SPIM_PIN_NOT_USED, you can control the pin manually in your application.

The code would be something like this:

#define SPIM_SS_PIN 3
uint8_t spi_xfer_done = 0;

void spim_event_handler(nrfx_spim_evt_t const * p_event,
                       void *                  p_context)
{
	if(spi_xfer_done == 0)
	{
		// Start second transfer
		APP_ERROR_CHECK(nrfx_spim_xfer(&spi, &xfer_desc, 0));
		spi_xfer_done++;
	}
	if(spi_xfer_done == 1)
	{
		// Second transfer done, deassert SS pin
		nrf_gpio_pin_set(SPIM_SS_PIN);
		spi_xfer_done = 2;
	}
}

vois spi_init(void)
{
    nrfx_spim_config_t spi_config = NRFX_SPIM_DEFAULT_CONFIG;
    spi_config.frequency      = NRF_SPIM_FREQ_1M;
    spi_config.ss_pin         = NRFX_SPIM_PIN_NOT_USED;
    spi_config.miso_pin       = NRFX_SPIM_MISO_PIN;
    spi_config.mosi_pin       = NRFX_SPIM_MOSI_PIN;
    spi_config.sck_pin        = NRFX_SPIM_SCK_PIN;
    APP_ERROR_CHECK(nrfx_spim_init(&spi, &spi_config, spim_event_handler, NULL));
	
	nrf_gpio_cfg_output(SPIM_SS_PIN);
	nrf_gpio_pin_set(SPIM_SS_PIN);
}

vois spi_transfer(void)
{
	spi_xfer_done = 0;
	// Assert SS pin before transfer
	nrf_gpio_pin_clear(SPIM_SS_PIN);
	
	APP_ERROR_CHECK(nrfx_spim_xfer(&spi, &xfer_desc, 0));
}

Best regards,
Jørgen