Sound level meter

Overview

As you rotate the volume, the number of LEDs light up in proportion to the amount of rotation. You can also turn on the number of LEDs according to the ambient volume with the microphone.

Leaf to use

Use the following leaves.

Type	Name	Q’ty
AI03	MIC&VR&LED	1
AP03	STM32 MCU	1
AV01	CR2032	1
AZ01	USB	1
AZ62	Connector Cover	1
	CR2032 coin cell battery	1
	M2*15mm screw	2

Assembly

Let’s assemble leaves as shown in the figure below.

Source code

Write the following program¹ in the Arduino IDE.

//=====================================================================
//  STM32 Sound level meter
//
//    (c) 2021 Trillion-Node Study Group
//    Released under the MIT license
//    https://opensource.org/licenses/MIT
//
//      Rev.00 2021/01/26  First release
//=====================================================================
#define LED1            PA8       // D6
#define LED2            PB12      // D7
#define LED3            PA9       // D8
#define LED4            PA10      // D9
#define LED5            PB6       // D10
#define LED6            PA7       // D11

#define MIC             PA1       // A2
#define VR              PB0       // A3

unsigned int dataVR;
unsigned int dataMic;

//-----------------------------------------------
// Get VR and MIC data
//-----------------------------------------------
void getSensorData()
{
    dataVR = analogRead(VR);
    dataMic = analogRead(MIC);

    Serial.println("---------------------");
    Serial.print("MIC  = ");
    Serial.println(dataMic,DEC);
    Serial.print("VR   = ");
    Serial.println(dataVR,DEC);
}

//-----------------------------------------------
// Turn the LEDs on and off according to the VR and MIC values.
//-----------------------------------------------
void dispSensorData()
{
    if (dataVR < 400)
    {
      digitalWrite(LED4,LOW);
      digitalWrite(LED5,LOW);
      digitalWrite(LED6,LOW);
    }
    else if (dataVR >= 400 && dataVR < 800)
    {
       digitalWrite(LED4,LOW);
       digitalWrite(LED5,LOW);
       digitalWrite(LED6,HIGH);
    }
    else if (dataVR >= 800 && dataVR < 900)
    {
       digitalWrite(LED4,LOW);
       digitalWrite(LED5,HIGH);
       digitalWrite(LED6,HIGH);
    }
    else
    {
       digitalWrite(LED4,HIGH);
       digitalWrite(LED5,HIGH);
       digitalWrite(LED6,HIGH);
    }

    if (dataMic < 300)
    {
      digitalWrite(LED1,LOW);
      digitalWrite(LED2,LOW);
      digitalWrite(LED3,LOW);
    }
    else if (dataMic >= 300 && dataMic < 350)
    {
      digitalWrite(LED1,LOW);
      digitalWrite(LED2,LOW);
      digitalWrite(LED3,HIGH);
    }
    else if (dataMic >= 350 && dataMic < 450)
    {
      digitalWrite(LED1,LOW);
      digitalWrite(LED2,HIGH);
      digitalWrite(LED3,HIGH);
    }
    else
    {
      digitalWrite(LED1,HIGH);
      digitalWrite(LED2,HIGH);
      digitalWrite(LED3,HIGH);
    }
}


void setup() {
  Serial.begin(115200);
  Serial.println("start!!");

  pinMode(LED1, OUTPUT);
  digitalWrite(LED1, LOW);
  pinMode(LED2, OUTPUT);
  digitalWrite(LED2, LOW);
  pinMode(LED3, OUTPUT);
  digitalWrite(LED3, LOW);
  pinMode(LED4, OUTPUT);
  digitalWrite(LED4, LOW);
  pinMode(LED5, OUTPUT);
  digitalWrite(LED5, LOW);
  pinMode(LED6, OUTPUT);
  digitalWrite(LED6, LOW);

  pinMode(MIC, INPUT);
  pinMode(VR, INPUT);

  // Startup test(LED)
  digitalWrite(LED1,HIGH);
  delay(200);
  digitalWrite(LED2,HIGH);
  delay(200);
  digitalWrite(LED3,HIGH);
  delay(200);
  digitalWrite(LED4,HIGH);
  delay(200);
  digitalWrite(LED5,HIGH);
  delay(200);
  digitalWrite(LED6,HIGH);
  delay(200);
  digitalWrite(LED1,LOW);
  digitalWrite(LED2,LOW);
  digitalWrite(LED3,LOW);
  digitalWrite(LED4,LOW);
  digitalWrite(LED5,LOW);
  digitalWrite(LED6,LOW);
  delay(200);
}


void loop() {
  getSensorData();
  dispSensorData();
  delay(100);
}

STM32_Sound_Level_Meter.ino

Execution Results

As you rotate the volume, the number of LEDs will light up according to the amount of rotation. The number of LEDs will light up according to the ambient volume, depending on the microphone.

Footnotes

1. The program differs from the AVR MUC leaf only in the designation of the pins. For more information, here. ↩