samples: cmsis_dsp: add moving average sample

samples/modules/cmsis_dsp/moving_average/CMakeLists.txt

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+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(moving_average)
+
+target_sources(app PRIVATE src/main.c)

samples/modules/cmsis_dsp/moving_average/README.rst

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+.. zephyr:code-sample:: cmsis-dsp-moving-average
+   :name: CMSIS-DSP moving average
+
+   Use the CMSIS-DSP library to calculate the moving average of a signal.
+
+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:
+
+.. code-block:: shell
+
+   west config manifest.project-filter -- +cmsis-dsp
+   west update cmsis-dsp
+
+Building and Running
+*********************
+
+The demo can be built as follows:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/modules/cmsis-dsp/moving_average
+   :host-os: unix
+   :board: qemu_cortex_m0
+   :goals: run
+   :compact:
+
+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.
+
+.. code-block:: console
+
+   *** 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

samples/modules/cmsis_dsp/moving_average/prj.conf

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+CONFIG_REQUIRES_FULL_LIBC=y
+CONFIG_REQUIRES_FLOAT_PRINTF=y
+
+CONFIG_CMSIS_DSP=y
+CONFIG_CMSIS_DSP_FILTERING=y

samples/modules/cmsis_dsp/moving_average/sample.yaml

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+sample:
+  description: Use CMSIS DSP to calculate moving average
+  name: CMSIS DSP Moving Average
+tests:
+  sample.modules.cmsis_dsp.moving_average:
+    tags:
+      - samples
+    integration_platforms:
+      - qemu_cortex_m0
+      - native_sim
+    modules:
+      - cmsis-dsp
+    harness: console
+    harness_config:
+      type: multi_line
+      regex:
+        - "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\\[04\\]:  0  0  0  0  0  0  1  2  3  4 | Output\\[04\\]:   1.00"
+        - "Input\\[05\\]:  0  0  0  0  0  1  2  3  4  5 | Output\\[05\\]:   1.50"
+        - "Input\\[06\\]:  0  0  0  0  1  2  3  4  5  6 | Output\\[06\\]:   2.10"
+        - "Input\\[07\\]:  0  0  0  1  2  3  4  5  6  7 | Output\\[07\\]:   2.80"
+        - "Input\\[08\\]:  0  0  1  2  3  4  5  6  7  8 | Output\\[08\\]:   3.60"
+        - "Input\\[09\\]:  0  1  2  3  4  5  6  7  8  9 | Output\\[09\\]:   4.50"
+        - "Input\\[10\\]:  1  2  3  4  5  6  7  8  9 10 | Output\\[10\\]:   5.50"
+        - "Input\\[11\\]:  2  3  4  5  6  7  8  9 10 11 | Output\\[11\\]:   6.50"
+        - "Input\\[12\\]:  3  4  5  6  7  8  9 10 11 12 | Output\\[12\\]:   7.50"
+        - "Input\\[13\\]:  4  5  6  7  8  9 10 11 12 13 | Output\\[13\\]:   8.50"
+        - "Input\\[14\\]:  5  6  7  8  9 10 11 12 13 14 | Output\\[14\\]:   9.50"
+        - "Input\\[15\\]:  6  7  8  9 10 11 12 13 14 15 | Output\\[15\\]:  10.50"
+        - "Input\\[16\\]:  7  8  9 10 11 12 13 14 15 16 | Output\\[16\\]:  11.50"
+        - "Input\\[17\\]:  8  9 10 11 12 13 14 15 16 17 | Output\\[17\\]:  12.50"
+        - "Input\\[18\\]:  9 10 11 12 13 14 15 16 17 18 | Output\\[18\\]:  13.50"
+        - "Input\\[19\\]: 10 11 12 13 14 15 16 17 18 19 | Output\\[19\\]:  14.50"
+        - "Input\\[20\\]: 11 12 13 14 15 16 17 18 19 20 | Output\\[20\\]:  15.50"
+        - "Input\\[21\\]: 12 13 14 15 16 17 18 19 20 21 | Output\\[21\\]:  16.50"
+        - "Input\\[22\\]: 13 14 15 16 17 18 19 20 21 22 | Output\\[22\\]:  17.50"
+        - "Input\\[23\\]: 14 15 16 17 18 19 20 21 22 23 | Output\\[23\\]:  18.50"
+        - "Input\\[24\\]: 15 16 17 18 19 20 21 22 23 24 | Output\\[24\\]:  19.50"
+        - "Input\\[25\\]: 16 17 18 19 20 21 22 23 24 25 | Output\\[25\\]:  20.50"
+        - "Input\\[26\\]: 17 18 19 20 21 22 23 24 25 26 | Output\\[26\\]:  21.50"
+        - "Input\\[27\\]: 18 19 20 21 22 23 24 25 26 27 | Output\\[27\\]:  22.50"
+        - "Input\\[28\\]: 19 20 21 22 23 24 25 26 27 28 | Output\\[28\\]:  23.50"
+        - "Input\\[29\\]: 20 21 22 23 24 25 26 27 28 29 | Output\\[29\\]:  24.50"
+        - "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"

samples/modules/cmsis_dsp/moving_average/src/main.c

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+/*
+ * Copyright (c) 2024 Benjamin Cabé <[email protected]>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <stdio.h>
+#include <zephyr/kernel.h>
+
+#include "arm_math.h"
+
+#define NUM_TAPS   10 /* Number of taps in the FIR filter (length of the moving average window) */
+#define BLOCK_SIZE 32 /* Number of samples processed per block */
+
+/*
+ * Filter coefficients are all equal for a moving average filter. Here, 1/NUM_TAPS = 0.1f.
+ */
+q31_t firCoeffs[NUM_TAPS] = {0x0CCCCCCD, 0x0CCCCCCD, 0x0CCCCCCD, 0x0CCCCCCD, 0x0CCCCCCD,
+			     0x0CCCCCCD, 0x0CCCCCCD, 0x0CCCCCCD, 0x0CCCCCCD, 0x0CCCCCCD};
+
+arm_fir_instance_q31 sFIR;
+q31_t firState[NUM_TAPS + BLOCK_SIZE - 1];
+
+int main(void)
+{
+	q31_t input[BLOCK_SIZE];
+	q31_t output[BLOCK_SIZE];
+	uint32_t start, end;
+
+	/* Initialize input data with a ramp from 0 to 31 */
+	for (int i = 0; i < BLOCK_SIZE; i++) {
+		input[i] = i << 24; /* Convert to Q31 format */
+	}
+
+	/* Initialize the FIR filter */
+	arm_fir_init_q31(&sFIR, NUM_TAPS, firCoeffs, firState, BLOCK_SIZE);
+
+	/* Apply the FIR filter to the input data and measure how many cycles this takes */
+	start = k_cycle_get_32();
+	arm_fir_q31(&sFIR, input, output, BLOCK_SIZE);
+	end = k_cycle_get_32();
+
+	printf("Time: %u us (%u cycles)\n", k_cyc_to_us_floor32(end - start), end - start);
+
+	for (int i = 0; i < BLOCK_SIZE; i++) {
+		printf("Input[%02d]: ", i);
+		for (int j = NUM_TAPS - 1; j >= 0; j--) {
+			if (j <= i) {
+				printf("%2d ", (int)(input[i - j] >> 24));
+			} else {
+				printf("%2d ", 0);
+			}
+		}
+		printf("| Output[%02d]: %6.2f\n", i, (double)output[i] / (1 << 24));
+	}
+
+	return 0;
+}