How to send 1 byte via SPI from master to slave

RE: How to send 1 byte via SPI from master to slave

IlyaM — Fri, 29 Jun 2018 14:38:20 GMT

Use uint8_t instead of or

RE: How to send 1 byte via SPI from master to slave

Markus Aerni — Fri, 29 Jun 2018 11:22:53 GMT

i had this problem too

if i enter the code like mentioned:

nrf_drv_spi_transfer(&spi, 0x11, 1, NULL, 1);

i get the following error:

Main.c(96): error: #167: argument of type "int" is incompatible with parameter of type "const uint8_t *"
nrf_drv_spi_transfer(&spi, 0x11, 1, NULL, 1);

RE: How to send 1 byte via SPI from master to slave

IlyaM — Fri, 05 May 2017 13:34:22 GMT

thank you! Hope it helps

RE: How to send 1 byte via SPI from master to slave

bjorn-spockeli — Fri, 05 May 2017 13:03:48 GMT

Then you'll have to use the last approach,

APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, 0x11, 1, NULL, 1));
APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, 0x20 | 0x00, 1, NULL, 1));
APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, 0x00, 1, rx_buf, 1));

with nrf_delay_ms(5) in between the calls.

RE: How to send 1 byte via SPI from master to slave

IlyaM — Fri, 05 May 2017 12:28:19 GMT

Yes, about 5ms. From data sheet: "The ADS129x serial interface decodes commands in bytes, and requires 4 tCLK periods to decode and execute. Therefore, when sending multibyte commands, a 4 tCLK period must separate the end of one byte (or opcode) and the next."

RE: How to send 1 byte via SPI from master to slave

bjorn-spockeli — Fri, 05 May 2017 11:05:47 GMT

No, the buffer length wil be ignored if the rx buffer pointer is NULL. Does it have to be exactly 5 microseconds between the transfers?

RE: How to send 1 byte via SPI from master to slave

IlyaM — Fri, 05 May 2017 09:03:11 GMT

Thanks for your reply. I found the solution of pin changes in examples of SDK.

So, about SPI, yes I need to send some data without receiving from MISO

According to your answer it looks like

APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, &SDATAC, 1, NULL, 1));

Do I need to change rx_buffer_length to 0?

So and how to implement the arduino code when I send each 1 byte after delay?

int out = 0;
digitalWrite(IPIN_CS, LOW);
SPI.transfer(0x20 | 0x00);
delayMicroseconds(5);
SPI.transfer(0);    // number of registers to be read/written – 1
delayMicroseconds(5);
out = SPI.transfer(0);
delayMicroseconds(1);
digitalWrite(IPIN_CS, HIGH);

What is the best way send like this:

uint8_t tx[3] = {0x11, 0x20 | 0x00, 0x00};

APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, 0x11, 1, NULL, 1));
APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, 0x20 | 0x00, 1, NULL, 1));
APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, 0x00, 1, rx_buf, 1));

RE: How to send 1 byte via SPI from master to slave

bjorn-spockeli — Fri, 05 May 2017 08:43:39 GMT

What is m_length set to? If you only want to send 1 byte then you have to set the rx_buffer_length 1 or p_rx_buffer to NULL if you do not need to receive any data.

APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, &SDATAC, 1, m_rx_buf, 1));

Otherwise you will just clock out "garbage data". As for the pin read issue, I would recommend setting up the gpiote peripheral to generate an interrupt whenever there is a level change on the pin, like the pin_change_int example in the SDK.

#include <stdbool.h>
#include "nrf.h"
#include "nrf_drv_gpiote.h"
#include "app_error.h"
#include "boards.h"

#define PIN_OUT 8
void in_pin_handler(nrf_drv_gpiote_pin_t pin, nrf_gpiote_polarity_t action)
{
    nrf_drv_gpiote_out_toggle(PIN_OUT);
}
/**
 * @brief Function for configuring: PIN_IN pin for input, PIN_OUT pin for output, 
 * and configures GPIOTE to give an interrupt on pin change.
 */
static void gpio_init(void)
{
    ret_code_t err_code;

    err_code = nrf_drv_gpiote_init();
    APP_ERROR_CHECK(err_code);
    
    nrf_drv_gpiote_out_config_t out_config = GPIOTE_CONFIG_OUT_SIMPLE(false);

    err_code = nrf_drv_gpiote_out_init(PIN_OUT, &out_config);
    APP_ERROR_CHECK(err_code);

    nrf_drv_gpiote_in_config_t in_config = GPIOTE_CONFIG_IN_SENSE_TOGGLE(true);
    in_config.pull = NRF_GPIO_PIN_PULLUP;

    err_code = nrf_drv_gpiote_in_init(PIN_IN, &in_config, in_pin_handler);
    APP_ERROR_CHECK(err_code);

    nrf_drv_gpiote_in_event_enable(PIN_IN, true);
}

/**
 * @brief Function for application main entry.
 */
int main(void)
{
    gpio_init();

    while (true)
    {
        // Do nothing.
    }
}