CMSIS-DSP: CFFT with Q15, wrong output

Hi,

I changed the CMSIS-DSP frequency bin example to Q15 format (or at least I'm trying to do so), but I'm getting wrong results. My changed code:

/* =================================================================================================

    for(testIndex = 0; testIndex < TEST_LENGTH_SAMPLES; testIndex++)

    for(testIndex = 0; testIndex < TEST_LENGTH_SAMPLES; testIndex++)

        testInput_f32_10khz_cfft[testIndex] /= 6.2f;     //divide the example test  data by 6.2 to get it in the range -1...+1

    testIndex = 0;

    arm_float_to_q15(testInput_f32_10khz_cfft, testInput_q15_10khz_cfft, TEST_LENGTH_SAMPLES);     //convert the data to Q15

    /* Process the data through the CFFT/CIFFT module */

    arm_cfft_q15(&arm_cfft_sR_q15_len1024, testInput_q15_10khz_cfft, ifftFlag, doBitReverse);

    /* Process the data through the Complex Magnitude Module for calculating the magnitude at each bin */

    arm_cmplx_mag_q15(testInput_q15_10khz_cfft, testOutput_q15_cfft, fftSize);    //output 2.14

    arm_shift_q15(testOutput_q15_cfft, 1, testOutput_q15_cfft, fftSize);            //convert to 1.15

    arm_q15_to_float(testOutput_q15_cfft, testOutput_q15_to_f32_cfft, 2048);  //for better readability in debug view

/* =================================================================================================

The output of this is:

0.0110473633, 0.000000000, 0.000000000, 0.000000000, 0.000000000, 0.000000000, 0.0110473633, 0.000000000,

0.000000000, 0.0110473633, 0.0110473633, 0.000000000, 0.000000000, 0.0110473633, 0.0191040039, 0.000000000,

0.000000000, 0.0110473633, 0.0191040039, 0.0110473633, 0.000000000, 0.0110473633, 0.000000000, 0.000000000,

0.0110473633, 0.000000000, 0.000000000, 0.000000000, 0.000000000, 0.000000000, 0.000000000, 0.000000000,

...

The output of the frequency bin example is:

89.4459534, 26.1034775, 35.7469597, 34.7221146, 49.2430763, 55.420784, 89.1215439, 20.6131191,

37.0284195, 98.7423096, 93.8422165, 63.7021141, 61.6773682, 84.585701, 123.891975, 25.0829983,

52.0468674, 74.8693924, 134.225296, 76.7762985, 16.0060749, 94.5713272, 65.412468, 24.5386391,

77.5796204, 56.8698654, 28.9609737, 18.5632, 26.0725956, 17.7821369, 24.5758419, 5.75964499,

...

I don't get where my error is. Except of the Q15 shift after the magnitude calculation, I (think I) do the same as in the frequency bin example. I know that I can't expect the same values since Q15 is in the range of -1...+1, but as the output shows, there are many zero values and most of the other values are identical. I expected to have values with the same ratios.

Any ideas what I'm doing wrong? I really don't see my error

Regards,

Ralf