I've been trying to get full-duplex mode running on my board, using this configuration (source: STM32F76xxx datasheet)
Using I2S_A (I2S_2) in master-rx and I2S_B (I2S_3) in slave-tx :
My I2S config bits (generated by SMT32CubeMX) are as follows:
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
RCC_PeriphCLKInitTypeDef PeriphClkInitStruct = {0};
/** Macro to configure the PLL multiplication factor
*/
__HAL_RCC_PLL_PLLM_CONFIG(16);
/** Macro to configure the PLL clock source
*/
__HAL_RCC_PLL_PLLSOURCE_CONFIG(RCC_PLLSOURCE_HSI);
/** Configure the main internal regulator output voltage
*/
__HAL_RCC_PWR_CLK_ENABLE();
__HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE3);
/** Initializes the CPU, AHB and APB busses clocks
*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
RCC_OscInitStruct.HSIState = RCC_HSI_ON;
RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
RCC_OscInitStruct.PLL.PLLM = 16;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
Error_Handler();
}
/** Initializes the CPU, AHB and APB busses clocks
*/
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
|RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
{
Error_Handler();
}
PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_I2S;
PeriphClkInitStruct.PLLI2S.PLLI2SN = 192;
PeriphClkInitStruct.PLLI2S.PLLI2SP = RCC_PLLP_DIV2;
PeriphClkInitStruct.PLLI2S.PLLI2SR = 2;
PeriphClkInitStruct.PLLI2S.PLLI2SQ = 2;
PeriphClkInitStruct.PLLI2SDivQ = 1;
PeriphClkInitStruct.I2sClockSelection = RCC_I2SCLKSOURCE_PLLI2S;
if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) != HAL_OK)
{
Error_Handler();
}
}
/**
* @brief I2S2 Initialization Function
* @param None
* @retval None
*/
static void MX_I2S2_Init(void)
{
/* USER CODE BEGIN I2S2_Init 0 */
/* USER CODE END I2S2_Init 0 */
/* USER CODE BEGIN I2S2_Init 1 */
/* USER CODE END I2S2_Init 1 */
hi2s2.Instance = SPI2;
hi2s2.Init.Mode = I2S_MODE_MASTER_RX;
hi2s2.Init.Standard = I2S_STANDARD_PHILIPS;
hi2s2.Init.DataFormat = I2S_DATAFORMAT_16B_EXTENDED;
hi2s2.Init.MCLKOutput = I2S_MCLKOUTPUT_ENABLE;
hi2s2.Init.AudioFreq = I2S_AUDIOFREQ_44K;
hi2s2.Init.CPOL = I2S_CPOL_LOW;
hi2s2.Init.ClockSource = I2S_CLOCK_PLL;
if (HAL_I2S_Init(&hi2s2) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN I2S2_Init 2 */
/* USER CODE END I2S2_Init 2 */
}
/**
* @brief I2S3 Initialization Function
* @param None
* @retval None
*/
static void MX_I2S3_Init(void)
{
/* USER CODE BEGIN I2S3_Init 0 */
/* USER CODE END I2S3_Init 0 */
/* USER CODE BEGIN I2S3_Init 1 */
/* USER CODE END I2S3_Init 1 */
hi2s3.Instance = SPI3;
hi2s3.Init.Mode = I2S_MODE_SLAVE_TX;
hi2s3.Init.Standard = I2S_STANDARD_PHILIPS;
hi2s3.Init.DataFormat = I2S_DATAFORMAT_16B_EXTENDED;
hi2s3.Init.MCLKOutput = I2S_MCLKOUTPUT_DISABLE;
hi2s3.Init.AudioFreq = I2S_AUDIOFREQ_44K;
hi2s3.Init.CPOL = I2S_CPOL_LOW;
hi2s3.Init.ClockSource = I2S_CLOCK_PLL;
if (HAL_I2S_Init(&hi2s3) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN I2S3_Init 2 */
/* USER CODE END I2S3_Init 2 */
}
/**
* @brief GPIO Initialization Function
* @param None
* @retval None
*/
static void MX_GPIO_Init(void)
{
/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOC_CLK_ENABLE();
__HAL_RCC_GPIOA_CLK_ENABLE();
__HAL_RCC_GPIOB_CLK_ENABLE();
}And this is my board wired up to my logic analyzer.
Board side (bottom): WHITE is MCK, GRAY is WS, PURPLE is SCK
LA side (top): PURPLE is SCK, GREEN is WS, MCK not pictured
Both MCK and WS read as expected (WS is a little slow, about 42kHz), but I'm not reading anything from the SCK pin(s).
I'm unclear why I can't get a read on the SCK pin. I would expect that internally the board's interface is functioning properly based on the other two signals, but my external device needs an SCK signal fed to it.
EDIT / UPDATE: SOLVED. I re-read the datasheet and noticed that the digital pins on the Nucleo board have DIFFERENT pin names than the I2S pins that are configured in STM32CubeMX when you select I2S under multimedia. I guess for anyone else who gets stuck in the future with this, in CubeMX you have enable I2S but you ALSO have to search on the MCU for the GPIO pins that are connected to the Nucleo peripherals and configure them separately.
