I'd like to know how to control the Neopixel LED.

Question

Hello

I'm trying to control the neopixeled WS2812. I referred to the following site.

I'm going to use this example of neopixel LED to control LED 3chain. I want to remove the Bluetooth function from this code and use only the control part of the LED, but there seems to be a problem with my code. This LEDs is connected to 5V, Gnd, I2S_SDIN_Pin(P0.26) on the nrf52DK board. But the LED doesn't work at all.
I don't know because it's my first time using I2S and neopixel LED. Can I get some help with this problem?

Thank you.


#include <stdio.h>
#include "nrf.h"
#include "nrf_drv_i2s.h"
#include "nrf_delay.h"
#include "app_util_platform.h"
#include "app_error.h"
#include "boards.h"

#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"


#define NLEDS 16
#define RESET_BITS 6
#define I2S_BUFFER_SIZE 3*NLEDS + RESET_BITS

static uint32_t m_buffer_tx[I2S_BUFFER_SIZE];
static volatile int nled = 1;

volatile uint8_t g_demo_mode = 0;
volatile bool g_i2s_start = true;
volatile bool g_i2s_running = false;

// This is the I2S data handler - all data exchange related to the I2S transfers
// is done here.
static void data_handler(uint32_t const * p_data_received,
                         uint32_t       * p_data_to_send,
                         uint16_t         number_of_words)
{
    // Non-NULL value in 'p_data_to_send' indicates that the driver needs
    // a new portion of data to send.
    if (p_data_to_send != NULL)
    {
        // do nothing - buffer is updated elsewhere
    }
}

/*
    caclChannelValue()
    Sets up a 32 bit value for a channel (R/G/B). 
    A channel has 8 x 4-bit codes. Code 0xe is HIGH and 0x8 is LOW.
    So a level of 128 would be represented as:
    0xe8888888
    The 16 bit values need to be swapped because of the way I2S sends data - right/left channels.
    So for the above example, final value sent would be:
    0x8888e888
*/
uint32_t caclChannelValue(uint8_t level)
{
    uint32_t val = 0;

    // 0 
    if(level == 0) {
        val = 0x88888888;
    }
    // 255
    else if (level == 255) {
        val = 0xeeeeeeee;
    }
    else {
        // apply 4-bit 0xe HIGH pattern wherever level bits are 1.
        val = 0x88888888;
        for (uint8_t i = 0; i < 8; i++) {
            if((1 << i) & level) {
                uint32_t mask = ~(0x0f << 4*i);
                uint32_t patt = (0x0e << 4*i);
                val = (val & mask) | patt;
            }
        }

        // swap 16 bits
        val = (val >> 16) | (val << 16);
    }

    return val;
}


// set LED data
void set_led_data()
{
    for(int i = 0; i < 3*NLEDS; i += 3) {
        if (i == 3*nled) {
            switch(g_demo_mode) 
            {
                case 0:
                {
                    m_buffer_tx[i] = 0x88888888;
                    m_buffer_tx[i+1] = caclChannelValue(128);
                    m_buffer_tx[i+2] = 0x88888888;
                }
                break;
                case 1:
                {
                    m_buffer_tx[i] = caclChannelValue(128);;
                    m_buffer_tx[i+1] = 0x88888888;
                    m_buffer_tx[i+2] = 0x88888888;
                }
                break;
                case 2:
                {
                    m_buffer_tx[i] = 0x88888888;
                    m_buffer_tx[i+1] = 0x88888888;
                    m_buffer_tx[i+2] = caclChannelValue(128);
                }
                break;
                default:
                break;
            }
        }
        else {
            m_buffer_tx[i] = 0x88888888;
            m_buffer_tx[i+1] = 0x88888888;
            m_buffer_tx[i+2] = 0x88888888;
        }
    }

    // reset 
    for(int i = 3*NLEDS; i < I2S_BUFFER_SIZE; i++) {
        m_buffer_tx[i] = 0;
    }
}

int main(void)
{
    uint32_t err_code = NRF_SUCCESS;

    err_code = NRF_LOG_INIT(NULL);
    APP_ERROR_CHECK(err_code);

    NRF_LOG_DEFAULT_BACKENDS_INIT();

    NRF_LOG_INFO("I2S loopback example started.");

    set_led_data(); //first time
    //I2S setting
    nrf_drv_i2s_config_t config = NRF_DRV_I2S_DEFAULT_CONFIG;
    // In Master mode the MCK frequency and the MCK/LRCK ratio should be
    // set properly in order to achieve desired audio sample rate (which
    // is equivalent to the LRCK frequency).
    // For the following settings we'll get the LRCK frequency equal to
    // 15873 Hz (the closest one to 16 kHz that is possible to achieve).
    config.sdin_pin  = I2S_SDIN_PIN; //26
    config.sdout_pin = I2S_SDOUT_PIN; //27
    config.mck_setup = NRF_I2S_MCK_32MDIV10; //< 32 MHz / 10 = 3.2 MHz.
    config.ratio     = NRF_I2S_RATIO_32X; //96X, //< LRCK = MCK / 32.
    config.channels  = NRF_I2S_CHANNELS_STEREO;

    err_code = nrf_drv_i2s_init(&config, data_handler);
    APP_ERROR_CHECK(err_code);


    for (;;)
    {
        // start I2S
        g_i2s_running = true;
        g_i2s_start = true;

        g_demo_mode = 2; //0~2

        // stop I2S
        //nrf_drv_i2s_stop();

        nrf_delay_ms(250);

        // update 
        if (g_i2s_running) 
        {
            nled = (nled + 1) % NLEDS;                
            set_led_data();
        }
    }
}

/** @} */