I am using the Cortex M4 with CMSIS 5.4.0 DSP library. I'm using the arm_rfft_f32() function and the max_arm_f32() function to compute the maximum frequency bin of injected pure sine wave with an external CODEC. SSI0 and uDMA are being used to take in the digital data.
When performing the RFFT and finding the max bin value, the bin value fluctuates between two adjacent bins. Therefore, the calculated frequency occasionally jumps due to these fluctuations.
I am wondering does anyone have experiencing using the arm_rfft_fast_f32()? Has anyone ever experienced this or does anyone have any suggestions as to how one might solve these fluctuating bin values?
I've discovered that the RFFT outputs the array in alternating real and imaginary components.As i only care about the real elements, I am now moving n+2 elements into another array where I find the bin with the max value. Unfortunately, It is still yielding the alternating results.