I was trying to use arm_rfft_q15 .In the CMSIS documentation for arm_rfft_q15, it says the output format is Q7.9 and 6 bits should be upscaled when the input RFFT size is 128 . Why does the amplitude have halved by using arm_rfft_q15 ? uint16_t i; fl...

I was trying to use arm_rfft_q15  .In the CMSIS documentation for arm_rfft_q15, it says the output format is Q7.9 and 6 bits should be upscaled when the input RFFT size is 128 . What is meant by this? Do I have to get the float values by dividing the...

I tried to compile and run arm_rfft_q15(STM32F030R8) .In STM32CubeIDE, I'm using libarm_cortexM0l_math.a, the file is in STM32Cube_FW_F0_V1.11.0\Drivers\CMSIS\Lib\GCC, one of the functions I'm using is arm_rfft_q15. Build error: undefined reference t...

I transplanted the general FFT algorithm ,but it took a lot of time for the CPU to run .I wonder if I can save time by using a Standard DSP library.