Published May 4, 2023 © CC BY-NC-SA

Stereo Digital FM Transmitter Circuit (Arduino Code)

IntermediateFull instructions provided2 hours1,785

Story

Without a doubt, FM transmitter and Receiver are among the top favorite electronic project topics, however, building a digital FM transmitter can be a challenging project for electronics enthusiasts. The transmitter can then be connected to a source of audio, such as a phone or computer, to broadcast music or other audio content.

In this project, I have introduced a compact stereo digital FM transmitter circuit that operates in the frequency range of 87MHz to 108MHz. The frequency can be adjusted using two tactile push-buttons, with a 0.1MHz step size. The heart of the circuit is an ATMega8 microcontroller, which communicates with a 0.96-inch SPI OLED display and the KT0803L FM transmitter chip via an I2C interface. You can directly connect a microphone or an AUX cable to the board to broadcast your desired sound, such as playing a piece of music from your cellphone, computer, … etc. After conducting some tests, it was found that the circuit operates quite stable, and the received sound is clear and sharp.

To design the schematic and PCB, I used Altium Designer 23 and shared the project with my friends to get their feedback and updates using Altium-365. The fast component search engine (Octopart) allowed me to quickly consider components’ information and also generate the BOM. To get high-quality fabricated boards, I sent the Gerber files to PCBWay. I am confident that utilizing this circuit will be an enjoyable and fulfilling experience for you.

Full Article + PCB:https://www.pcbway.com/blog/technology/Stereo_Digital_FM_Transmitter_Circuit_64d799f3.html

Code

Code

#include <FMTX.h>
#include <SPI.h>
#include "SSD1306Ascii.h"
#include "SSD1306AsciiSpi.h"


#define CS_PIN 7
#define RST_PIN 9
#define DC_PIN 8
#define Down_Key 15
#define UP_Key 14


float frequency = 87.0;
float tolerance = 0.001;


SSD1306AsciiSpi oled;


void setup() {
  fmtx_init(frequency, EUROPE);
  oled.begin(&Adafruit128x64, CS_PIN, DC_PIN, RST_PIN);
  oled.setFont(Adafruit5x7);


  pinMode(Down_Key, INPUT);
  pinMode(UP_Key, INPUT);


  oled.clear();
  oled.set2X();
  oled.println("   FM-TR   ");
  oled.setRow(3);
  oled.setCol(40);
  oled.set2X();
  fmtx_set_freq(frequency);
  oled.println(frequency, 1);
}


void loop() {
  if (digitalRead(Down_Key) == 0 && frequency > 87.0) {
    delay(130);
    frequency = frequency - 0.1;
    fmtx_set_freq(frequency);
    if (frequency < 100.0) {
      oled.setRow(3);
      oled.println("           ");
      oled.setRow(3);
      oled.setCol(40);
      oled.println(frequency, 1);
    }
    if ((frequency - 100.0) >= -tolerance) {
      oled.setRow(3);
      oled.println("           ");
      oled.setRow(3);
      oled.setCol(35);
      oled.println(frequency, 1);
    }
  }
  if (digitalRead(UP_Key) == 0 && frequency < 108.0) {
    delay(130);
    frequency = frequency + 0.1;
    fmtx_set_freq(frequency);
    if (frequency < 100.0) {
      oled.setRow(3);
      oled.println("           ");
      oled.setRow(3);
      oled.setCol(40);
      oled.println(frequency, 1);
    }
    if ((frequency - 100.0) >= -tolerance) {
      oled.setRow(3);
      oled.println("           ");
      oled.setRow(3);
      oled.setCol(35);
      oled.println(frequency, 1);
    }
  }
}

Credits

Hesam Moshiri

51 projects • 32 followers

https://www.youtube.com/c/MyVanitar/videos

Stereo Digital FM Transmitter Circuit (Arduino Code)

Story

Schematics

PCB

Code

Code

Credits

Hesam Moshiri

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Stereo Digital FM Transmitter Circuit (Arduino Code)

Stereo Digital FM Transmitter Circuit (Arduino Code)

Story

Schematics

PCB

Code

Code

Credits

Hesam Moshiri

Comments

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