Hi,
I want to implement a speech IO using stm32f401 discovery board.
In this case I am using the onboard digital microphone to acquire the PDM samples using spi2(I2S) interface. After that I am using the PDM filter to convert the PDM samples to PCM
samples .The respective code(code reused) snippet is given below.
void AUDIO_REC_SPI_IRQHANDLER(void)
{
uint16_t volume;
uint16_t app;
/* Check if data are available in SPI Data register */
if (SPI_GetITStatus(SPI2, SPI_I2S_IT_RXNE) != RESET)
{
app = SPI_I2S_ReceiveData(SPI2);
In_Buf[InternalBufferSize++] = HTONS(app);
/* Check to prevent overflow condition */
if (InternalBufferSize >= INTERNAL_BUFF_SIZE)
{
InternalBufferSize = 0;
volume = 10;
PDM_Filter_64_LSB((uint8_t *)In_Buf, (uint16_t *)Out_Buf, volume ,(PDMFilter_InitStruct *)&Filter_var);
Data_Status = 1;
}
}
}
where
uint16_t In_Buf[INTERNAL_BUFF_SIZE];//PDM sample buffer
uint16_t Out_Buf[OUT_BUFF_SIZE];//PCM sample buffer
&
#define INTERNAL_BUFF_SIZE 128 //PDM in_buffer size
#define OUT_BUFF_SIZE 16 //PCM out_buffer size
In this way I am collecting the PCM samples in Out_Buf.
So my question here is how to send the mono speech pcm samples from Out_Buf to audio codec so that I will get perfect output without distortion.
As per my understanding I have done the coding like this(descrided below).
while(1)
{
if(Data_Status)
{
GPIO_SetBits(GPIOD,GPIO_Pin_13);//orange led = PCM data available indicator
if (SPI_I2S_GetFlagStatus(CODEC_I2S, SPI_I2S_FLAG_TXE))
{
SPI_I2S_SendData(CODEC_I2S, sample);
//update only on every second sample to insure that L & R ch. have the same sample value
if (sampleCounter & 0x00000001)
{
sample = Out_Buf[sample_index++];
//f_sample = fir_filter(sample);//filter the samples & send to codec
if(sample_index>=OUT_BUFF_SIZE) sample_index=0;
}
sampleCounter++;
}///if end for data transmission
if (sampleCounter==16000)
{
GPIO_SetBits(GPIOD,GPIO_Pin_15);//blue=sample counter indicator
}
else if (sampleCounter == 32000)
{
GPIO_ResetBits(GPIOD,GPIO_Pin_15);
sampleCounter = 0;
}
}//if end for PCM data available
}//while end
The problem is that I am not getting the correct output.
So kindly explain me where is the problem & how to solve this.
Tools - KEIL IDE
Board - STM32F401 DISCO
Thanks & Regards
Satyabrata Senapati
