I have done further measurements, the DMA halfbuffer length is 1024. I have 20 samples for one wavelength. 1024/20 results in 51,2 Wave lengths per halfbuffer. When I measure on the oscilloscope the glitch happens exactly at every 51,2 wavelengths. Could it be that the DMA does something strange?
Here is the code for the DMA init:
static void MX_DMA_Init(void)
{
/* DMA controller clock enable */
__HAL_RCC_DMA1_CLK_ENABLE();
__HAL_RCC_DMA2_CLK_ENABLE();
/* DMA interrupt init */
/* DMA1_Stream5_IRQn interrupt configuration */
HAL_NVIC_SetPriority(DMA1_Stream5_IRQn, 0, 0);
HAL_NVIC_EnableIRQ(DMA1_Stream5_IRQn);
/* DMA2_Stream0_IRQn interrupt configuration */
HAL_NVIC_SetPriority(DMA2_Stream0_IRQn, 0, 0);
HAL_NVIC_EnableIRQ(DMA2_Stream0_IRQn);
}
for the DMA callback:
//callback functions
void HAL_ADC_ConvHalfCpltCallback(ADC_HandleTypeDef* hadc)
{
//first half of adc is full
inbufPtr= &adc_val[0];
outbufPtr= &dac_val[DATASIZE];
processDSP();
}
void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc)
{
inbufPtr= &adc_val[DATASIZE];
outbufPtr= &dac_val[0];
processDSP();
}
and the DSP function where the DMA is filled:
void processDSP(void)
{
/*update buffers and and NCOs-------------------*/
for(int i=0;i<DATASIZE;i++)
{
//fill output buffer
outbufPtr[i]=(int)(2048+1000*cos_table[nco_f0.index]);
//read input into a buffer
incomming_buffer[i]=(float)inbufPtr[i]*ADC_gain; //ADC_gain=3.3/4095
//update local cosine and sine buffers
local_cosine_buffer[i]=cos_table[nco_f0.index];
local_sine_buffer[i]=-sin_table[nco_f0.index];
local_rect_buffer[i]=rect_table[nco_f0.index];
//update NCO
update_NCO(&nco_f0, COSINE_TABLE_SIZE);
}
I hope you can help
Regards
