SPI spi_transceive not receiving data

[dmleone]

my master is outputting all the right signals on the SPI lines. The slave though, although it appears ot recognize the CSN pin and runs the spi_tranceieve function. It does not actually read the MOSI line. I am using 2x nRF52850DK boards. and using the nrf52840dk_nrf52840.dts file and wrapping it with an overlay. i got 2 print command that show it waits at the spi_transceive line until it sees a csn trigger. but it never actually fills the rx buffer.

master overlay

&pinctrl {
	spi1_default: spi1_default {
		group1 {
			psels = <NRF_PSEL(SPIM_SCK, 0, 31)>,
				<NRF_PSEL(SPIM_MOSI, 0, 30)>,
				<NRF_PSEL(SPIM_MISO, 0, 10)>;
		};
	};

	spi1_sleep: spi1_sleep {
		group1 {
			psels = <NRF_PSEL(SPIM_SCK, 0, 31)>,
				<NRF_PSEL(SPIM_MOSI, 0, 30)>,
				<NRF_PSEL(SPIM_MISO, 0, 10)>;
			low-power-enable;
		};
	};
};

&spi1 {
	compatible = "nordic,nrf-spim";
	pinctrl-0 = <&spi1_default>;
	pinctrl-1 = <&spi1_sleep>;
	pinctrl-names = "default", "sleep";
	cs-gpios = <&gpio0 4 GPIO_ACTIVE_LOW>;
};

master SPI output command

int spi_write_cmd(uint8_t cmd){
	int err;
	int incr = 0;

	tx_buffer[0] = cmd;
	tx_buffer[1] = 0x33;
	tx_buffer[2] = 0xff;
	err = spi_transceive(spi_dev, &spi_cfg, &tx, &rx);
	if(err > 0){
		while(incr < MAX_BUFFER_SIZE){
			printk("0x%X", rx_buffer[incr]);
			incr++;
		}
		printk("\n");
	}
	return err;
}

slave overlay

&pinctrl {
	spi2_default: spi2_default {
		group1 {
			psels = <NRF_PSEL(SPIS_SCK, 0, 10)>,
					<NRF_PSEL(SPIS_MOSI, 0, 21)>,
					<NRF_PSEL(SPIS_MISO, 0, 23)>,
					<NRF_PSEL(SPIS_CSN, 0, 16)>;
		};
	};

	spi2_sleep: spi2_sleep {
		group1 {
			psels = <NRF_PSEL(SPIS_SCK, 0, 10)>,
					<NRF_PSEL(SPIS_MOSI, 0, 21)>,
					<NRF_PSEL(SPIS_MISO, 0, 23)>,
					<NRF_PSEL(SPIS_CSN, 0, 16)>;
			low-power-enable;
		};
	};
};

&spi2 {
	compatible = "nordic,nrf-spis";
	status = "okay";
	pinctrl-0 = <&spi2_default>;
	/delete-property/ pinctrl-1;
	pinctrl-names = "default";
	def-char = <0x33>;
};

slave read function

int spis_transceive(void){
	int cnt = 0;
	uint8_t incr = 0;
	printk("pre trans_spi\n");
	cnt = spi_transceive(spis_dev, &spis_cfg, &spis_tx, &spis_rx);
	printk("post spi_trans cnt: %d\n", cnt);

	if(cnt > 0){
		while(incr < SPI_BUFFER_SIZE){
			printk("0x%X", spis_rx_buffer[incr]);
			incr++;
		}
		printk("\n");
	}

	return cnt;

slave output: every time i send a command over SPI it registers the the CSN pin activity, but the spi_transceieve function does not do anything or fill the buffer.

post spi_trans cnt: 0
pre trans_spi
post spi_trans cnt: 0
pre trans_spi
post spi_trans cnt: 0
pre trans_spi

complete slave code

#include "spis.h"
#include <zephyr.h>
#include <sys/printk.h>
#include <drivers/spi.h>
#include <device.h>

#define SPIS_NODE DT_NODELABEL(spi2)

extern void spis_thread(void *, void *, void *);

K_THREAD_DEFINE(spis_tid, SPIS_STACK_SIZE, spis_thread, NULL, NULL, NULL, SPIS_PRIORITY, 0, 0);
		
struct spis_cb_t spi_cb;

static uint8_t spis_tx_buffer[SPI_BUFFER_SIZE] = "<*>slave out default message buf";
static uint8_t spis_rx_buffer[SPI_BUFFER_SIZE];

static struct spi_config spis_cfg = {
	.operation = SPI_WORD_SET(8) | SPI_TRANSFER_MSB |
		     SPI_OP_MODE_SLAVE
			 | SPI_MODE_CPOL | SPI_MODE_CPHA,
	.frequency = 125000,
	.slave = 1,
	//.cs = &spi_cs,
};

const struct spi_buf spis_tx_buf = { 
	.buf = spis_tx_buffer,
	.len = sizeof(spis_tx_buffer)
};

const struct spi_buf_set spis_tx = {
	.buffers = &spis_tx_buf,
	.count = 1
};

const struct spi_buf spis_rx_buf = 	{ 
	.buf = spis_rx_buffer,
	.len = sizeof(spis_rx_buffer),
};

const struct spi_buf_set spis_rx =	{ 
	.buffers = &spis_rx_buf,
	.count = 1 
};

const struct device *spis_dev;

uint8_t spis_init(void)
{
	int err;

	spis_tx_buffer[0] = 0xff;
	spis_tx_buffer[1] = 0x35;
	spis_dev = device_get_binding(DT_LABEL(SPIS_NODE));

	if (spis_dev == NULL) {
		printk("Could not get %s device\n", DT_LABEL(SPIS_NODE));
		return 1;
	}
	printk("SPI Device: %s\n", DT_LABEL(SPIS_NODE));

	return 0;
}

int spis_transceive(void){
	int cnt = 0;
	uint8_t incr = 0;
	printk("pre trans_spi\n");
	cnt = spi_transceive(spis_dev, &spis_cfg, &spis_tx, &spis_rx);
	printk("post spi_trans cnt: %d\n", cnt);

	if(cnt > 0){
		while(incr < SPI_BUFFER_SIZE){
			printk("0x%X", spis_rx_buffer[incr]);
			incr++;
		}
		printk("\n");
	}

	return cnt;
}

extern void spis_thread(void *unused1, void *unused2, void *unused3){
	int err;
	
	err = spis_init();
	if(err) return;
	if(!device_is_ready(spis_dev)) return;

	printk("SPIS thread begin\n");

	while (1) {
		err = spis_transceive();
		if(err < 0) break;
	}
	printk("SPIS thread end\n");
}

[Jørgen Holmefjord]

Hi,

Have you tried using different pins?

GPIO P0.10 is by default connected to the NFCT antenna on the nRF52840 DK. If you want to use this pin as a GPIO, you need to write UICR->NFCPINS register to 0.

If you are using the pin headers on the DK, you also need to move the 0R resistor on the DK.

Best regards,
Jørgen

[dmleone]

I have tried changing pins to all kinds of different arrangements actually. 

My first pin arrangement was using the pins listed in the .dts file for spi2. I noticed those were being shared with qspi, so i disabled that. that didnt work. so then i started moving to various different pins hoping it was just an input pin problem.

Do you have 4 pins you can recommend for me to try that are not being used by anything within the DK?

[Jørgen Holmefjord]

You can have a look at Connector interface in the nRF52840 DK documentation. P0.02-P0.04, P0.26-P0.31, P1.01-P1.08 and P1.10-P1.15 should be available. Note that some samples might use some of these pins for other purposes (analog inputs, TWI/SPI interfaces, etc).