Using CMSIS DSP on STM32F746ZG for FIR filtering

Hi!

We're trying to use the CMSIS DSP library to filter a real-time signal using the CMSIS dsp fir function. We are using the STM32746ZG board. 

We've calculated the coefficients in C and they are correct according to MATLAB. We're feeding these into the arm_fir_init_f32() and we cannot get it to work. When the filter order is 2, i.e. coefficients are 0,1,0 - The output is the same as the input. When we increase the order the output becomes mostly noise. The filter coefficients doesn't seem to be used at all.

Buffer definitions:

float32_t ADCBUFFER[length]={0};

float32_t DACBUFFER[length]={0};

ADCBUFFER and DACBUFFER are circular buffers using DMA with length = 1000.

ADC init:

hadc1.Instance = ADC1;

hadc1.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV4;

hadc1.Init.Resolution = ADC_RESOLUTION_12B;

hadc1.Init.ScanConvMode = DISABLE;

hadc1.Init.ContinuousConvMode = ENABLE;

hadc1.Init.DiscontinuousConvMode = DISABLE;

hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_RISING;

hadc1.Init.ExternalTrigConv = ADC_EXTERNALTRIGCONV_T6_TRGO;

hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;

hadc1.Init.NbrOfConversion = 1;

hadc1.Init.DMAContinuousRequests = ENABLE;

hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;

DAC init:

sConfig.DAC_Trigger = DAC_TRIGGER_T6_TRGO;

sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;

TIM6 init:

htim6.Instance = TIM6;

htim6.Init.Prescaler = 0;

htim6.Init.CounterMode = TIM_COUNTERMODE_UP;

htim6.Init.Period = tim6Period;

htim6.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;

System clock: 192MHz
HCLK: 192MHz
APB1 peripheral clocks: 12MHz
APB1 timer clocks: 24MHz
APB2 peripheral clocks: 48MHz
APB2 timer clocks: 96MHz

Using DSP FIR:

float32_t * firStateF32 = calloc(sizeof(float32_t) * (blocksize+numTaps-1), 1);

arm_fir_instance_f32 S;

arm_fir_init_f32(&S, numTaps, filterCoeff, firStateF32, blockSize);

while (1)

{

arm_fir_f32(&S, ADCBUFFER, DACBUFFER, blockSize);　

}

free(firStateF32);

The array filterCoeff is generated by another function (using sample rate = 800kHz) and ordered as described in the CMSIS DSP lib info.

What is missing to get the arm_fir_f32() to work properly?

Thanks in advance!