Using an AVR microcontroller with Zephyr to read data from an ADC via SPI

#include <zephyr.h>
#include <device.h>
#include <drivers/spi.h>
#include <logging/log.h>

LOG_MODULE_REGISTER(main);

#define ADC_SPI DT_NODELABEL(adc)

static const struct spi_config spi_cfg = {
    .frequency = 1000000U,
    .operation = SPI_WORD_SET(8) | SPI_TRANSFER_MSB,
    .slave = 0,
    .cs = NULL,
};

void main(void) {
    const struct device *spi_dev = DEVICE_DT_GET(ADC_SPI);

    if (!device_is_ready(spi_dev)) {
        LOG_ERR("SPI device not ready");
        return;
    }

    uint8_t tx_buf[1] = {0x00}; // Dummy data to trigger ADC read
    uint8_t rx_buf[2];
    struct spi_buf tx = {.buf = tx_buf, .len = sizeof(tx_buf)};
    struct spi_buf rx = {.buf = rx_buf, .len = sizeof(rx_buf)};
    struct spi_buf_set tx_set = {.buffers = &tx, .count = 1};
    struct spi_buf_set rx_set = {.buffers = &rx, .count = 1};

    int ret = spi_transceive(spi_dev, &spi_cfg, &tx_set, &rx_set);
    if (ret) {
        LOG_ERR("SPI transceive failed: %d", ret);
        return;
    }

    int adc_value = (rx_buf[0] << 8) | rx_buf[1];
    LOG_INF("ADC Value: %d", adc_value);
}