I am trying to use the DFSDM in parallel mode. However my output sample rate is significantly lower than expected.
My input is an MEMS microphone, with 2.048MHz leading to 128kS/s of 16bit samples that arrive at the MPU.
The desired output is 32kS/s PCM.
My filters are configured as follows (everything except for Continuous mode is done by CubeMX)
hdfsdm1_filter0.RegularContMode = DFSDM_CONTINUOUS_CONV_ON;
hdfsdm1_filter0.Instance = DFSDM1_Filter0;
hdfsdm1_filter0.Init.RegularParam.Trigger = DFSDM_FILTER_SW_TRIGGER;
hdfsdm1_filter0.Init.RegularParam.FastMode = DISABLE;
hdfsdm1_filter0.Init.RegularParam.DmaMode = DISABLE;
hdfsdm1_filter0.Init.FilterParam.SincOrder = DFSDM_FILTER_SINC3_ORDER;
hdfsdm1_filter0.Init.FilterParam.Oversampling = 64;
hdfsdm1_filter0.Init.FilterParam.IntOversampling = 1;
if (HAL_DFSDM_FilterInit(&hdfsdm1_filter0) != HAL_OK)
{
Error_Handler();
}
hdfsdm1_channel0.Instance = DFSDM1_Channel0;
hdfsdm1_channel0.Init.OutputClock.Activation = DISABLE;
hdfsdm1_channel0.Init.OutputClock.Selection = DFSDM_CHANNEL_OUTPUT_CLOCK_SYSTEM;
hdfsdm1_channel0.Init.OutputClock.Divider = 1;
hdfsdm1_channel0.Init.Input.Multiplexer = DFSDM_CHANNEL_INTERNAL_REGISTER;
hdfsdm1_channel0.Init.Input.DataPacking = DFSDM_CHANNEL_STANDARD_MODE;
hdfsdm1_channel0.Init.Input.Pins = DFSDM_CHANNEL_SAME_CHANNEL_PINS;
hdfsdm1_channel0.Init.SerialInterface.Type = DFSDM_CHANNEL_SPI_RISING;
hdfsdm1_channel0.Init.SerialInterface.SpiClock = DFSDM_CHANNEL_SPI_CLOCK_EXTERNAL;
hdfsdm1_channel0.Init.Awd.FilterOrder = DFSDM_CHANNEL_FASTSINC_ORDER;
hdfsdm1_channel0.Init.Awd.Oversampling = 1;
hdfsdm1_channel0.Init.Offset = 0x00;
hdfsdm1_channel0.Init.RightBitShift = 0x00;
if (HAL_DFSDM_ChannelInit(&hdfsdm1_channel0) != HAL_OK)
{
Error_Handler();
}
if (HAL_DFSDM_FilterConfigRegChannel(&hdfsdm1_filter0, DFSDM_CHANNEL_0, DFSDM_CONTINUOUS_CONV_ON) != HAL_OK)
{
Error_Handler();
}
The code writing and reading is done as follows (result is the input, use is an indicator if there is new data available):
DFSDM_Channel_HandleTypeDef channel = hdfsdm1_channel0;
DFSDM_Filter_HandleTypeDef filter = hdfsdm1_filter0;
channel.Instance->CHDATINR = result & 0xffff;
use = false;
if (filter.Instance->FLTISR & DFSDM_FLTISR_REOCF) {
use = true;
result = filter.Instance->FLTRDATAR >> 16;
}
If my understanding is correct, I believe I need 64x oversampling. However, when I do select 64x oversampling, I only get ~500 Samples per second.
When I set the oversampling to 4x, I get 8kS/s. But setting the oversampling ration to 1x, I get 64kS/s.
Since I discovered that I am apparently unable to properly reset the filters, I always reset the MCU after changing the filter configuration.
