CMSIS-DSP moving average

Overview

This sample demonstrates how to use the CMSIS-DSP library to calculate the moving average of a signal.

It can be run on any board supported in Zephyr, but note that CMSIS-DSP is specifically optimized for ARM Cortex-A and Cortex-M processors.

A moving average filter is a common method used for smoothing noisy data. It can be implemented as a finite impulse response (FIR) filter where the filter coefficients are all equal to 1/N, where N is the number of “taps” (i.e. the size of the moving average window).

The sample uses a very simple input signal of 32 samples, and computes the moving average using a “window” of 10 samples. The resulting output is computed in one single call to the arm_fir_q31() CMSIS-DSP function, and displayed on the console.

Note

In order to allow an easy comparison of the efficiency of the CMSIS-DSP library when used on ARM processors vs. other architectures, the sample outputs the time and number of cycles it took to compute the moving average.

Requirements

CMSIS-DSP is an optional module and needs to be added explicitly to your Zephyr workspace:

west config manifest.project-filter -- +cmsis-dsp
west update cmsis-dsp

Building and Running

The demo can be built as follows:

west build -b qemu_cortex_m0 samples/modules/cmsis_dsp/moving_average
west build -t run

The sample will output the number of cycles it took to compute the moving averages, as well as the computed average for each 10-sample long window of the input signal.

*** Booting Zephyr OS build v3.6.0-224-gb55824751d6c ***
Time: 244 us (244 cycles)
Input[00]:  0  0  0  0  0  0  0  0  0  0 | Output[00]:   0.00
Input[01]:  0  0  0  0  0  0  0  0  0  1 | Output[01]:   0.10
Input[02]:  0  0  0  0  0  0  0  0  1  2 | Output[02]:   0.30
Input[03]:  0  0  0  0  0  0  0  1  2  3 | Output[03]:   0.60
...
Input[30]: 21 22 23 24 25 26 27 28 29 30 | Output[30]:  25.50
Input[31]: 22 23 24 25 26 27 28 29 30 31 | Output[31]:  26.50