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How to store and manage ADC values in a 2D array for FFT processing in an FMCW radar system

I am using an FMCW radar to determine the distance and speed of a moving object with an STM32L476 microcontroller. To find the range of a stationary object, I store the ADC values into the "fft_in" array using the "HAL_ADC_ConvCpltCallback" function. I have initialized "is_data_ready_for_fft = 1" as follows:

void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef *hadc1) {
    is_data_ready_for_fft = 1;
}

void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef *hadc1) {
    is_data_ready_for_fft = 1;
}

Then, I calculate the range using FFT. Now, I need to store this 1D array of ADC values in a 2D array to calculate the Doppler frequency across the chirp index.
The code that copies ADC values into the fft_in array and performs the range calculation is in the file below ()

Here is the desired matrix structure, where each fft_in array at different times forms rows of the matrix:

[0,0] = fft_in(0)[0],  [0,1] = fft_in(0)[1],  ...,  [0,512] = fft_in(0)[512]
[1,0] = fft_in(1)[0],  [1,1] = fft_in(1)[1],  ...,  [1,512] = fft_in(1)[512]
[2,0] = fft_in(2)[0],  [2,1] = fft_in(2)[1],  ...,  [2,512] = fft_in(2)[512]
...
[19,0] = fft_in(19)[0], [19,1] = fft_in(19)[1], ..., [19,512] = fft_in(19)[512]
#The chirp index is taken as 20, and the number of samples is 512. Thus, FFT across rows yields range, and FFT across columns yields velocity.

[0,0] = fft_in(0)[0],  [0,1] = fft_in(0)[1],  ...,  [0,512] = fft_in(0)[512]
[1,0] = fft_in(1)[0],  [1,1] = fft_in(1)[1],  ...,  [1,512] = fft_in(1)[512]
[2,0] = fft_in(2)[0],  [2,1] = fft_in(2)[1],  ...,  [2,512] = fft_in(2)[512]
...
[19,0] = fft_in(19)[0], [19,1] = fft_in(19)[1], ..., [19,512] = fft_in(19)[512]
#The chirp index is taken as 20, and the number of samples is 512. Thus, FFT across rows yields range, and FFT across columns yields velocity.

Solution

Yes, precisely!

@Sterling As you proceed through each chirp, that will store your {fft_in} array into the matrix row by row. After that, you may examine the matrix to calculate the velocity or any other desired parameter.

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How to store and manage ADC values in a 2D array for FFT processing in an FMCW radar system

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