RE: FFT

Charlie — Mon, 17 Mar 2025 11:12:47 GMT

Hi David,

It depends on which SDK and chip you are using now.

For nRF5 SDK, it includes an FPU FFT example that demonstrates how to use the FPU peripheral with the CMSIS DSP library for FFT calculations.

The example generates sine data (with and without noise) and processes it with FFT every 1 second. It's available in the SDK at: <InstallFolder>\examples\peripheral\fpu_fft

To use the CMSIS DSP library for FFT processing:

Include the arm_math.h header
Add the precompiled library to your project (e.g., libarm_cortexM4lf_math.a for Cortex-M4 with floating point)

The example works with Keil, IAR, and GCC environments, and can be used with or without a SoftDevice. There are also versions with FPU interrupt handling (with _irq postfix) available.

FPU FFT Example provides more details on testing the example.

For Zephyr RTOS, there is no direct FFT sample, but you can refer to a CMSIS-DSP moving average sample that demonstrates using the CMSIS-DSP library, which could be adapted for FFT processing.

Best regards,

Charlie