Yes, that's exactly why I am here. I am new to SAI and audio. Do you have any good resources that I can use to learn more about SAI? The biggest question that I have is, am I approaching the theory of stereo audio right with my buffer? Can one have two different things playing out the Left and Right side simply by putting the Left data in odd indicies and the Right data in even indicies on the same buffer? Let's assume for a moment that I had everything configured correctly. Or is that the root of the problem? How do I tell my codec / SAI config where to get R data and L data from?
Also, the code does have four channels, but I am only using one of them:
Looks like stereo is being implemented in the Main function in the SAI init:
static void MX_SAI1_Init(void)
{
/* USER CODE BEGIN SAI1_Init 0 */
/* USER CODE END SAI1_Init 0 */
/* USER CODE BEGIN SAI1_Init 1 */
/* USER CODE END SAI1_Init 1 */
hsai_BlockA1.Instance = SAI1_Block_A;
hsai_BlockA1.Init.AudioMode = SAI_MODEMASTER_TX;
hsai_BlockA1.Init.Synchro = SAI_ASYNCHRONOUS;
hsai_BlockA1.Init.OutputDrive = SAI_OUTPUTDRIVE_DISABLE;
hsai_BlockA1.Init.NoDivider = SAI_MASTERDIVIDER_ENABLE;
hsai_BlockA1.Init.FIFOThreshold = SAI_FIFOTHRESHOLD_EMPTY;
hsai_BlockA1.Init.ClockSource = SAI_CLKSOURCE_PLLSAI;
hsai_BlockA1.Init.AudioFrequency = SAI_AUDIO_FREQUENCY_48K;
hsai_BlockA1.Init.SynchroExt = SAI_SYNCEXT_DISABLE;
hsai_BlockA1.Init.MonoStereoMode = SAI_STEREOMODE;
hsai_BlockA1.Init.CompandingMode = SAI_NOCOMPANDING;
hsai_BlockA1.Init.TriState = SAI_OUTPUT_NOTRELEASED;
if (HAL_SAI_InitProtocol(&hsai_BlockA1, SAI_I2S_STANDARD, SAI_PROTOCOL_DATASIZE_16BIT, 2) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN SAI1_Init 2 */
/* USER CODE END SAI1_Init 2 */
}
Been a while, but I finally tried your suggestion of a sawtooth wave:
You can see that example below in my oscilloscope capture of the sawtooth wave.
I generated my data in Octave (alternative to MATLAB) and copied over to the STM32 IDE in C. Here are my graphs of a sawtooth and sine wave:
I combine them into one array of 1000 data points with the sawtooth data in the odd indices and the sine data in the even indices:
So, if the stereo sound was truly coming out L for even indices and R for odd indices, we should see a sawtooth on one side and a sine on the other side. The data being fed into the wave is good based on the graphs above! This is what I get when I run on one side on the STM board, however:
I think this looks similar to the last picture where all the data is graphed, so maybe it's trying to output both the sine and the sawtooth wave at the same time and the codec is filtering or smoothing it out?
Here is what it looks like with just a sawtooth data in the indices:
So I am back to my original issue. I can output a single waveform on both left and right. I cannot make left and right independent. I hope it's a simple misunderstanding on my part of how to do this, or something that I need to configure, and not a limitation of the technote on the Discovery board.
Your image say more info as all texts.
SDIN LRCK on scope you check if have two channels if yes all problem is as i write in
if(ret == AUDIO_OK)
{
/* Initialize the audio codec internal registers */
if (audio_drv->Init(AUDIO_I2C_ADDRESS,
OutputDevice,
Volume,
AudioFreq) != AUDIO_OK)
{
ret = AUDIO_ERROR;
}
}
return ret;This code init CS chip mode and as i mark on image in speaker mode have only one channel then maybe for both HP+SPEAKER demo set mono mix mode usw...
Try write your own CS chip init.
You are coder then write code and not only odd even data in array...
