Solved
STM32L4 DFSDM clipping
Any ideas why values would be non linear in the approximately the upper 1 to 2 bits?
For the setup below, it is linear to between -17000 to +14000. Doubling the + output only yields around +18000. These are raw values. This really acts like an overflow somewhere it seems to me. Test input is DC, in this case using an AMC3336 TI modulator.
What am I missing here?
Setup:
static void MX_DFSDM1_Init(void)
{
/* USER CODE BEGIN DFSDM1_Init 0 */
/* USER CODE END DFSDM1_Init 0 */
/* USER CODE BEGIN DFSDM1_Init 1 */
/* USER CODE END DFSDM1_Init 1 */
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 = 256;
hdfsdm1_filter0.Init.FilterParam.IntOversampling = 4;
if (HAL_DFSDM_FilterInit(&hdfsdm1_filter0) != HAL_OK)
{
Error_Handler();
}
hdfsdm1_channel0.Instance = DFSDM1_Channel0;
hdfsdm1_channel0.Init.OutputClock.Activation = ENABLE;
hdfsdm1_channel0.Init.OutputClock.Selection = DFSDM_CHANNEL_OUTPUT_CLOCK_SYSTEM;
hdfsdm1_channel0.Init.OutputClock.Divider = 12;
hdfsdm1_channel0.Init.Input.Multiplexer = DFSDM_CHANNEL_EXTERNAL_INPUTS;
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_INTERNAL;
hdfsdm1_channel0.Init.Awd.FilterOrder = DFSDM_CHANNEL_SINC3_ORDER;
hdfsdm1_channel0.Init.Awd.Oversampling = 1;
hdfsdm1_channel0.Init.Offset = 0;
hdfsdm1_channel0.Init.RightBitShift = 11;
if (HAL_DFSDM_ChannelInit(&hdfsdm1_channel0) != HAL_OK)
{
Error_Handler();
}
if (HAL_DFSDM_FilterConfigRegChannel(&hdfsdm1_filter0, DFSDM_CHANNEL_0, DFSDM_CONTINUOUS_CONV_OFF) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN DFSDM1_Init 2 */
/* USER CODE END DFSDM1_Init 2 */
}Read:
int32_t readAMC3336(uint32_t samples) {
int32_t value;
uint32_t channel = 0;
HAL_DFSDM_FilterRegularStart(&hdfsdm1_filter0);
HAL_StatusTypeDef result = HAL_DFSDM_FilterPollForRegConversion(&hdfsdm1_filter0, 10);
value = HAL_DFSDM_FilterGetRegularValue(&hdfsdm1_filter0, &channel);
return value;
}
