nRF52840 SPIM help

Question

Hi,

It has been a while since I looked up on different resources to get SPI slave transaction example and I finally found on the `nrf/samples/tfm/tfm_secure_peripheral/secure_peripheral_partition` something that may fit my requirements.

To be more precise, I'm looking for a way to drive an OLED display with IC SSD1333 over SPI (MISO not required) and Data Control pin.

Here is my try:

#include <zephyr/zephyr.h>
#include <nrfx_spim.h>

#define CS_PIN          16 /* P0.16 */
#define SCK_PIN         19 /* P0.19 */
#define DC_PIN          20 /* P0.20 */
#define MOSI_PIN        32 /* P1.0 */

typedef uint8_t BYTE;

BYTE tx_buffer[5] = { 0xAF, 0x01, 0xFF, 0x01, 0x01 }; // Random test data to probe

static void spim_init(uint32_t sck_pin, uint32_t mosi_pin, uint32_t cs_pin, uint32_t dc_pin) {
	nrf_spim_pins_set(NRF_SPIM3, sck_pin, mosi_pin, NRF_SPIM_PIN_NOT_CONNECTED);
  nrf_spim_dcx_pin_set(NRF_SPIM3, dc_pin);
  nrf_spim_dcx_cnt_set(NRF_SPIM3, 1);
	nrf_spim_configure(NRF_SPIM3, NRF_SPIM_MODE_2, NRF_SPIM_BIT_ORDER_MSB_FIRST);
	nrf_spim_csn_configure(NRF_SPIM3, CS_PIN, NRF_SPIM_CSN_POL_LOW, 0);
	nrf_spim_frequency_set(NRF_SPIM3, NRF_SPIM_FREQ_2M);
	nrf_spim_int_enable(NRF_SPIM3, NRF_SPIM_INT_ENDTX_MASK);
	nrf_spim_enable(NRF_SPIM3);
}

static void sendTest() {
  nrf_spim_tx_buffer_set(NRF_SPIM3, tx_buffer, 5);
  nrf_spim_rx_buffer_set(NRF_SPIM3, NULL, 0);

  nrf_spim_task_trigger(NRF_SPIM3, NRF_SPIM_TASK_START);

  nrf_spim_event_clear(NRF_SPIM3, NRF_SPIM_EVENT_ENDTX);
}

int init_SSD1333_display() {
  spim_init(SCK_PIN, MOSI_PIN, CS_PIN, DC_PIN);

  sendTest();
}

The problem is I can't figure it out why I've only the MOSI pin that seems to work properly when I probe the SPI's outputs.

Indeed, CS stays HIGH despite NRF_SPIM_CSN_POL_LOW configuration and SCK doesn't show up the clock signal. Also, Data control pin does not change after the first byte sent (

nrf_spim_dcx_cnt_set set to 1)

Where am I wrong ?

Thanks !

EDIT:

I put

nrf_spim_disable(NRF_SPIM3);

at the beginning of spim_init function and changed the pin declaration to

#define CS_PIN          40 /* P1.08 */
#define SCK_PIN         5 /* P0.05 */
#define DC_PIN          30 /* P0.30 */
#define MOSI_PIN        32 /* P1.0 */

and was able to get SCK, CS and Data Control working normally...

So my question is : is there something to consider with pins initialisation before giving them to SPIM ? The pins used previously didn't seems used.

Simonr · Accepted Answer

Hi 
 I assume you're working on an nRF52840 DK, is that correct? If so, it makes sense that only the MOSI pin works in your initial pin configuration, as P0.16 on the DK is by default connected to a LED, and P0.19 and P0.20 are connected to the onboard external memory. There are instructions on which solder bridges to cut/short in order to make these GPIOs work if you want to use these specifically in the DK user guide. 
 Best regards, 
 Simon

nRF52840 SPIM help

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