• MCU board: External STM32F407 board
• Framework: STM32 HAL / STM32CubeIDE
• Purpose: Generate I2S audio clocks/data and configure PCM1795 over SPI/control pins.

C
#include "main.h"
#include <string.h>

I2S_HandleTypeDef hi2s3;
SPI_HandleTypeDef hspi1;

#define DAC_CS_GPIO_Port     GPIOA
#define DAC_CS_Pin           GPIO_PIN_4
#define DAC_RST_GPIO_Port    GPIOA
#define DAC_RST_Pin          GPIO_PIN_0
#define DAC_MUTE_GPIO_Port   GPIOA
#define DAC_MUTE_Pin         GPIO_PIN_1

static void dac_cs_low(void)  { HAL_GPIO_WritePin(DAC_CS_GPIO_Port, DAC_CS_Pin, GPIO_PIN_RESET); }
static void dac_cs_high(void) { HAL_GPIO_WritePin(DAC_CS_GPIO_Port, DAC_CS_Pin, GPIO_PIN_SET); }

static HAL_StatusTypeDef pcm1795_write_reg(uint8_t reg, uint8_t value) {
    uint8_t frame[2];
    frame[0] = reg;
    frame[1] = value;
    dac_cs_low();
    HAL_StatusTypeDef st = HAL_SPI_Transmit(&hspi1, frame, sizeof(frame), HAL_MAX_DELAY);
    dac_cs_high();
    return st;
}

static void pcm1795_reset_sequence(void) {
    HAL_GPIO_WritePin(DAC_RST_GPIO_Port, DAC_RST_Pin, GPIO_PIN_RESET);
    HAL_Delay(10);
    HAL_GPIO_WritePin(DAC_RST_GPIO_Port, DAC_RST_Pin, GPIO_PIN_SET);
    HAL_Delay(10);
}

static void pcm1795_init(void) {
    dac_cs_high();
    HAL_GPIO_WritePin(DAC_MUTE_GPIO_Port, DAC_MUTE_Pin, GPIO_PIN_SET);
    pcm1795_reset_sequence();

    // TODO: Replace register addresses/values with the exact PCM1795 board mode.
    // Configure audio format, oversampling, de-emphasis, and mute control per PCM1795 datasheet.
    // pcm1795_write_reg(REGISTER_ADDR, REGISTER_VALUE);

    HAL_GPIO_WritePin(DAC_MUTE_GPIO_Port, DAC_MUTE_Pin, GPIO_PIN_RESET);
}

int main(void) {
    HAL_Init();
    SystemClock_Config();
    MX_GPIO_Init();
    MX_SPI1_Init();
    MX_I2S3_Init();

    pcm1795_init();

    // Example 16-bit stereo silence buffer. Replace with real PCM stream.
    uint16_t silence[128] = {0};

    while (1) {
        HAL_I2S_Transmit(&hi2s3, silence, 128, HAL_MAX_DELAY);
    }
}

1. Create an STM32CubeIDE project for the exact STM32F407 board.
2. Enable one SPI peripheral in I2S master transmit mode for BCK/LRCK/DATA/MCLK.
3. Enable one SPI peripheral or GPIO bit-banged interface for PCM1795 control.
4. Map the GPIO labels above to the actual header pins used on the STM32F407 board.
5. Build and flash with ST-LINK or the board's onboard programmer.

• Confirm exact STM32F407 board model and available I2S pins.
• Confirm PCM1795 board pinout and whether MCLK is required.
• Confirm PCM1795 register settings for I2S word length, sample rate, and analog output mode.