class and example

.gitignore

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+.pio
+.vscode/.browse.c_cpp.db*
+.vscode/c_cpp_properties.json
+.vscode/launch.json
+.vscode/ipch

.vscode/extensions.json

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+{
+    // See http://go.microsoft.com/fwlink/?LinkId=827846
+    // for the documentation about the extensions.json format
+    "recommendations": [
+        "platformio.platformio-ide"
+    ]
+}

include/README

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+
+This directory is intended for project header files.
+
+A header file is a file containing C declarations and macro definitions
+to be shared between several project source files. You request the use of a
+header file in your project source file (C, C++, etc) located in `src` folder
+by including it, with the C preprocessing directive `#include'.
+
+```src/main.c
+
+#include "header.h"
+
+int main (void)
+{
+ ...
+}
+```
+
+Including a header file produces the same results as copying the header file
+into each source file that needs it. Such copying would be time-consuming
+and error-prone. With a header file, the related declarations appear
+in only one place. If they need to be changed, they can be changed in one
+place, and programs that include the header file will automatically use the
+new version when next recompiled. The header file eliminates the labor of
+finding and changing all the copies as well as the risk that a failure to
+find one copy will result in inconsistencies within a program.
+
+In C, the usual convention is to give header files names that end with `.h'.
+It is most portable to use only letters, digits, dashes, and underscores in
+header file names, and at most one dot.
+
+Read more about using header files in official GCC documentation:
+
+* Include Syntax
+* Include Operation
+* Once-Only Headers
+* Computed Includes
+
+https://gcc.gnu.org/onlinedocs/cpp/Header-Files.html

lib/README

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+
+This directory is intended for project specific (private) libraries.
+PlatformIO will compile them to static libraries and link into executable file.
+
+The source code of each library should be placed in a an own separate directory
+("lib/your_library_name/[here are source files]").
+
+For example, see a structure of the following two libraries `Foo` and `Bar`:
+
+|--lib
+|  |
+|  |--Bar
+|  |  |--docs
+|  |  |--examples
+|  |  |--src
+|  |     |- Bar.c
+|  |     |- Bar.h
+|  |  |- library.json (optional, custom build options, etc) https://docs.platformio.org/page/librarymanager/config.html
+|  |
+|  |--Foo
+|  |  |- Foo.c
+|  |  |- Foo.h
+|  |
+|  |- README --> THIS FILE
+|
+|- platformio.ini
+|--src
+   |- main.c
+
+and a contents of `src/main.c`:
+```
+#include <Foo.h>
+#include <Bar.h>
+
+int main (void)
+{
+  ...
+}
+
+```
+
+PlatformIO Library Dependency Finder will find automatically dependent
+libraries scanning project source files.
+
+More information about PlatformIO Library Dependency Finder
+- https://docs.platformio.org/page/librarymanager/ldf.html

platformio.ini

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+; PlatformIO Project Configuration File
+;
+;   Build options: build flags, source filter
+;   Upload options: custom upload port, speed and extra flags
+;   Library options: dependencies, extra library storages
+;   Advanced options: extra scripting
+;
+; Please visit documentation for the other options and examples
+; https://docs.platformio.org/page/projectconf.html
+
+[env:esp32dev]
+platform = espressif32
+board = esp32dev
+framework = arduino
+monitor_speed = 115200

src/hamming.cpp

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+#include <stdlib.h>
+#include <math.h>
+#include <Arduino.h>
+#include "hamming.h"
+
+#define PI 3.14159265358979323846
+
+Hamming::Hamming(int window_size)
+{
+    //Save actual windows size.
+    m_window_size = window_size;
+
+    //Allocate the memory for the constants
+    m_coef = static_cast<float *>(malloc(sizeof(float) * m_window_size));
+
+    // create the constants for a hamming window
+    const float arg =  (2.0 * PI) / window_size;
+    for (int i = 0; i < window_size; i++)
+    {
+        float n_coef_value = 0.54 - (0.46 * cos(arg * (i+ 0.5)));
+        m_coef[i] = n_coef_value;
+    }
+}
+
+Hamming::~Hamming()
+{
+    free(m_coef);
+}
+
+void Hamming::applyWindow(float *input)
+{
+    for (int i = 0; i < m_window_size; i++)
+        input[i] = input[i] * m_coef[i];
+}
+
+void Hamming::showCoefficients(void)
+{
+    int i;
+    for (i = 0; i < m_window_size - 1; i++)
+        { 
+            Serial.printf("%.4f",m_coef[i]);
+            Serial.print(',');
+        }
+
+    Serial.printf("%.4f",m_coef[i]);
+}

src/hamming.h

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+#include <inttypes.h>
+
+class Hamming
+{
+private:
+    float *m_coef;
+    int m_window_size;
+
+public:
+    Hamming(int window_size);
+    ~Hamming();
+    void applyWindow(float *input);
+    void showCoefficients(void);
+
+};

src/main.cpp

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+#include <Arduino.h>
+#include <hamming.h>
+
+#define WINDOW_SIZE 1000
+
+Hamming hamming_window(WINDOW_SIZE);
+
+// positive part of a heavyside function.
+float heavyside_function[WINDOW_SIZE];
+
+
+void setup() {
+  Serial.begin(115200);
+
+}
+
+void loop() {
+  int j = 0;
+
+  // Forming the heavyside function.
+  for (int i = 0; i < WINDOW_SIZE; i++)
+    heavyside_function[i] = 1;
+
+  hamming_window.applyWindow(heavyside_function);
+
+  // Print the response of a hamming window.
+
+  for (int j = 0; j < WINDOW_SIZE -1 ; j++)
+  {
+    Serial.printf("%.04f", heavyside_function[j]);
+    Serial.print(',');
+  }
+    Serial.printf("%.04f", heavyside_function[j]);
+
+  Serial.println("");
+  Serial.println("");
+
+  //If you want to just see the coefficients
+  // hamming_windoW.showCoefficients();
+
+  vTaskDelay(5000);
+}

test/README

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+
+This directory is intended for PlatformIO Unit Testing and project tests.
+
+Unit Testing is a software testing method by which individual units of
+source code, sets of one or more MCU program modules together with associated
+control data, usage procedures, and operating procedures, are tested to
+determine whether they are fit for use. Unit testing finds problems early
+in the development cycle.
+
+More information about PlatformIO Unit Testing:
+- https://docs.platformio.org/page/plus/unit-testing.html