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ESP-32-C3 0.42 OLED ESP-NOW Wifi PWM

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ESP-32-C3 0.42 OLED ESP-NOW Wifi PWM

Posted: Sun Jul 27, 2025 6:06 pm
by Jateu_01
Hi all,

I get to the point right now I have various learning difficulties. I can do anything hands on, but coding is troublesome. I've dabbled with electronics but coding certainly Isn't my thing.

It would be amazing if I could get some guidance and help regarding my project.

Essentially the project is ESP-NOW based, Master detects analogue input from hall effect sensor and sends signal to slave to output a pwm signal.

Is there any projects out there that do this or anyone will to advise.

Again I am not skilled or expert at coding. Please excuse and issues.

Many Thanks.

Re: ESP-32-C3 0.42 OLED ESP-NOW Wifi PWM

Posted: Mon Jul 28, 2025 4:59 am
by horace99
test ESP-NOW, WiFI, OLD, switches, PWM, etc in a separate programs - when all is working start building your project

e.g. initially get the ESP-NOW communications working then worry about connecting sensors etc
start with example library code from File>Examples>ESP_NOW
once you have working example code you can adapt it to suit your project

can you give a link to your OLED display?
for PWM have a look at https://lastminuteengineers.com/esp32-pwm-tutorial/

Re: ESP-32-C3 0.42 OLED ESP-NOW Wifi PWM

Posted: Mon Jul 28, 2025 8:07 am
by horace99
found an example ESP-NOW code which may help
NOTE: ESP-NOW has changed from ESP32 core 2.x to 3.x - see https://docs.espressif.com/projects/esp ... p_now.html
you may find some of the example code online is using ESP32 core V2

ESP-NOW transmitter works using a ESP32-C3-MINI-1 IDE 2.3.5 ESP32 core 3.3.0

Code: Select all

// ESP32 Transmitter - two way communication using ESP_NOW
// NOTE: updated to use ESP32 core V3.x
//  note- no sensors so test data structure transmitted

// original code from
/*
  Rui Santos
  Complete project details at https://RandomNerdTutorials.com/esp-now-two-way-communication-esp32/
  
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files.
  
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
*/

#include <esp_now.h>
#include <WiFi.h>

//#include <Wire.h>
//#include <Adafruit_Sensor.h>
//#include <Adafruit_BME280.h>


//Adafruit_BME280 bme;

// initially test with broadcast address - sends to all receivers
//uint8_t broadcastAddress[] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff};  // ESP-NOW broadcast address
// REPLACE WITH THE MAC Address of your receiver
uint8_t broadcastAddress[] = { 0x68, 0xB6, 0xB3, 0x2C, 0x16, 0x08};

// Define variables to store BME280 readings to be sent
float temperature = 3.14159;
float humidity = 90.0;
float pressure = 10.0;

// Define variables to store incoming readings
float incomingTemp;
float incomingHum;
float incomingPres;

// Variable to store if sending data was successful
String success;

//Structure example to send data
//Must match the receiver structure
typedef struct struct_message {
  float temp;
  float hum;
  float pres;
} struct_message;

// Create a struct_message called BME280Readings to hold sensor readings
struct_message BME280Readings;

// Create a struct_message to hold incoming sensor readings
struct_message incomingReadings;
bool incomingReadingsOK = false;

esp_now_peer_info_t peerInfo;

// Callback when data is sent
void OnDataSent(const esp_now_send_info_t* mac_addr, esp_now_send_status_t status) {
  Serial.print("Last Packet Send Status:\t");
  Serial.println(status == ESP_NOW_SEND_SUCCESS ? "Delivery Success" : "Delivery Fail");
  if (status == 0) success = "Delivery Success :)";
  else success = "Delivery Fail :(";
}

// Callback when data is received
void OnDataRecv(const esp_now_recv_info_t* mac, const unsigned char* incomingData, int len) {
  memcpy(&incomingReadings, incomingData, sizeof(incomingReadings));
  Serial.printf("From %02X:%02X:%02X:%02X:%02X:%02X",
                mac->src_addr[0], mac->src_addr[1], mac->src_addr[2], mac->src_addr[3], mac->src_addr[4], mac->src_addr[5]);
  Serial.printf(" Bytes received: %d\n", len);
  incomingTemp = incomingReadings.temp;
  incomingHum = incomingReadings.hum;
  incomingPres = incomingReadings.pres;
  incomingReadingsOK = true;
}

void setup() {
  // Init Serial Monitor
  Serial.begin(115200);
  delay(3000);
  Serial.println("\n\n **** ESP-NOW transmitter *****");
  // Init BME280 sensor
  /*bool status = bme.begin(0x76);  
  if (!status) {
    Serial.println("Could not find a valid BME280 sensor, check wiring!");
   // while (1);
  }*/

  // Set device as a Wi-Fi Station
  WiFi.mode(WIFI_STA);
  delay(100);  // short delay for initialisation
  Serial.print("WiFi MAC address ");
  Serial.println(WiFi.macAddress());
  // Init ESP-NOW
  if (esp_now_init() != ESP_OK) {
    Serial.println("Error initializing ESP-NOW");
    return;
  }
  delay(100);  // short delay for initialisation
  byte mac[6];
  WiFi.macAddress(mac);
  Serial.printf("ESP-NOW initialised MAC address %02X:%02X:%02X:%02X:%02X:%02X\n",
                mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
  // Once ESPNow is successfully Init, we will register for Send CB to
  // get the status of Trasnmitted packet
  esp_now_register_send_cb(OnDataSent);

  // Register peer
  memcpy(peerInfo.peer_addr, broadcastAddress, 6);
  peerInfo.channel = 0;
  peerInfo.encrypt = false;

  // Add peer
  if (esp_now_add_peer(&peerInfo) != ESP_OK) {
    Serial.println("Failed to add peer");
    return;
  }
  // Register for a callback function that will be called when data is received
  esp_now_register_recv_cb(OnDataRecv);
}

void loop() {
  getReadings();
  // Set values to send
  BME280Readings.temp = temperature;
  BME280Readings.hum = humidity;
  BME280Readings.pres = pressure;
  // Send message via ESP-NOW
  esp_err_t result = esp_now_send(broadcastAddress, (uint8_t*)&BME280Readings, sizeof(BME280Readings));
  if (result == ESP_OK) Serial.println("esp_now_send() returns ESP_OK");
  else                  Serial.println("esp_now_send() returns Error");
  updateDisplay();
  delay(10000);
}

void getReadings() {
  static int x = 1;
  temperature = 23.5 + x;  //bme.readTemperature();
  humidity = 78 + x;       //bme.readHumidity();
  pressure = 21 + x;       //(bme.readPressure() / 100.0F);
  x++;
}

void updateDisplay() {
  if (!incomingReadingsOK) return;
  // Display Readings in Serial Monitor
  Serial.println("INCOMING READINGS");
  Serial.print("Temperature: ");
  Serial.print(incomingReadings.temp);
  Serial.println(" ºC");
  Serial.print("Humidity: ");
  Serial.print(incomingReadings.hum);
  Serial.println(" %");
  Serial.print("Pressure: ");
  Serial.print(incomingReadings.pres);
  Serial.println(" hPa");
  Serial.println();
}
ESP_NOW receiver using a ESP32-S3-DevKitC-1

Code: Select all

// ESP32 Receiver - two way communication using ESP_NOW
//  NOTE: updated to use ESP32 core V3.x
//  waits to receive packet from transmitter then transmits data back
//  note- no sensors so test data structure transmitted

// original code from
/*
  Rui Santos
  Complete project details at https://RandomNerdTutorials.com/esp-now-two-way-communication-esp32/
  
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files.
  
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
*/

#include <esp_now.h>
#include <WiFi.h>

//#include <Wire.h>
//#include <Adafruit_Sensor.h>
//#include <Adafruit_BME280.h>
//Adafruit_BME280 bme;

// this will be setup when a packet is received with transmitter MAC adddress
uint8_t broadcastAddress[] = { 0, 0, 0, 0, 0, 0 };  //{ 0xEC, 0x64, 0xC9, 0x82, 0x7D, 0x34 };  //{0x84, 0xCC, 0xA8, 0x7A, 0x56, 0x6C};

// Define variables to store BME280 readings to be sent
float temperature;
float humidity;
float pressure;

// Define variables to store incoming readings
float incomingTemp;
float incomingHum;
float incomingPres;

// Variable to store if sending data was successful
String success;

//Structure example to send data
//Must match the receiver structure
typedef struct struct_message {
  float temp;
  float hum;
  float pres;
} struct_message;

// Create a struct_message called BME280Readings to hold sensor readings
struct_message BME280Readings;

// Create a struct_message to hold incoming sensor readings
struct_message incomingReadings;

esp_now_peer_info_t peerInfo;

// Callback when data is sent
void OnDataSent(const esp_now_send_info_t* mac_addr, esp_now_send_status_t status) {
  Serial.print("Last Packet Send Status:\t");
  Serial.println(status == ESP_NOW_SEND_SUCCESS ? "Delivery Success" : "Delivery Fail");
  if (status == 0) success = "Delivery Success :)";
  else success = "Delivery Fail :(";
}

// Callback when data is received
void OnDataRecv(const esp_now_recv_info_t* mac, const unsigned char* incomingData, int len) {
  memcpy(&incomingReadings, incomingData, sizeof(incomingReadings));
  // if no broadcast address set it up to transmitter MAC
  if (broadcastAddress[0] == 0) {
    memcpy(broadcastAddress, mac->src_addr, 6);       // set broadcasrAddress to received MAC address
    memcpy(peerInfo.peer_addr, broadcastAddress, 6);  // Register peer
    peerInfo.channel = 0;
    peerInfo.encrypt = false;
    // Add peer
    if (esp_now_add_peer(&peerInfo) != ESP_OK) {
      Serial.println("Failed to add peer");
      return;
    }
  }
  // display transmitter MAC address and copy data
  Serial.printf("From %02X:%02X:%02X:%02X:%02X:%02X",
                mac->src_addr[0], mac->src_addr[1], mac->src_addr[2], mac->src_addr[3], mac->src_addr[4], mac->src_addr[5]);
  Serial.printf(" Bytes received: %d\n", len);
  incomingTemp = incomingReadings.temp;
  incomingHum = incomingReadings.hum;
  incomingPres = incomingReadings.pres;
}

void setup() {
  // Init Serial Monitor
  Serial.begin(115200);
  delay(3000);
  // Init BME280 sensor
  //bool status = bme.begin(0x76);
  //if (!status) {
  //  Serial.println("Could not find a valid BME280 sensor, check wiring!");
  // while (1);
  //}
  Serial.println("\n\n **** ESP-NOW receiver *****");
  // Set device as a Wi-Fi Station
  WiFi.mode(WIFI_STA);
  delay(100);  // short delay for initialisation
  Serial.print("WiFi MAC address ");
  Serial.println(WiFi.macAddress());
  // Init ESP-NOW
  if (esp_now_init() != ESP_OK) {
    Serial.println("Error initializing ESP-NOW");
    return;
  }
  Serial.print("ESP-NOW initialised");
  // Once ESPNow is successfully Init, we will register for Send CB to
  // get the status of Trasnmitted packet
  esp_now_register_send_cb(OnDataSent);
  // Register for a callback function that will be called when data is received
  esp_now_register_recv_cb(OnDataRecv);
}

void loop() {
  delay(10000);
  getReadings();
  // Set values to send
  BME280Readings.temp = temperature;
  BME280Readings.hum = humidity;
  BME280Readings.pres = pressure;
  // Send message via ESP-NOW
  if (broadcastAddress[0] == 0)
    Serial.println("no MAC address to transmit too");
  else {
    esp_err_t result = esp_now_send(broadcastAddress, (uint8_t*)&BME280Readings, sizeof(BME280Readings));
    Serial.printf("Send too %02X:%02X:%02X:%02X:%02X:%02X ",
                  broadcastAddress[0], broadcastAddress[1], broadcastAddress[2], broadcastAddress[3], broadcastAddress[4], broadcastAddress[5]);
   if (result == ESP_OK) Serial.println("esp_now_send() returns ESP_OK");
  else                  Serial.println("esp_now_send() returns Error");
    updateDisplay();
  }
}
void getReadings() {
  static int x = 1;
  temperature = 33.5 + x;  //bme.readTemperature();
  humidity = 88 + x;       //bme.readHumidity();
  pressure = 212 + x;      //(bme.readPressure() / 100.0F);
  x++;
}

void updateDisplay() {
  // Display Readings in Serial Monitor
  Serial.println("INCOMING READINGS");
  Serial.print("Temperature: ");
  Serial.print(incomingReadings.temp);
  Serial.println(" ºC");
  Serial.print("Humidity: ");
  Serial.print(incomingReadings.hum);
  Serial.println(" %");
  Serial.print("Pressure: ");
  Serial.print(incomingReadings.pres);
  Serial.println(" hPa");
  Serial.println();
}
test run transmitter output

Code: Select all

**** ESP-NOW transmitter *****
WiFi MAC address 10:91:A8:02:00:E8
ESP-NOW initialised MAC address 10:91:A8:02:00:E8
esp_now_send() returns ESP_OK
Last Packet Send Status:	Delivery Success
From 68:B6:B3:2C:16:08 Bytes received: 12
esp_now_send() returns ESP_OK
INCOMING READINGS
Temperature: 36.50 ºC
Humidity: 91.00 %
Pressure: 215.00 hPa

Last Packet Send Status:	Delivery Success
From 68:B6:B3:2C:16:08 Bytes received: 12
esp_now_send() returns ESP_OK
INCOMING READINGS
Temperature: 37.50 ºC
Humidity: 92.00 %
Pressure: 216.00 hPa

Last Packet Send Status:	Delivery Success
From 68:B6:B3:2C:16:08 Bytes received: 12
esp_now_send() returns ESP_OK
INCOMING READINGS
Temperature: 38.50 ºC
Humidity: 93.00 %
Pressure: 217.00 hPa

Last Packet Send Status:	Delivery Success
From 68:B6:B3:2C:16:08 Bytes received: 12
esp_now_send() returns ESP_OK
INCOMING READINGS
Temperature: 39.50 ºC
Humidity: 94.00 %
Pressure: 218.00 hPa

Last Packet Send Status:	Delivery Success
From 68:B6:B3:2C:16:08 Bytes received: 12
esp_now_send() returns ESP_OK
INCOMING READINGS
Temperature: 40.50 ºC
Humidity: 95.00 %
Pressure: 219.00 hPa
receiver output

Code: Select all

**** ESP-NOW receiver *****
WiFi MAC address 68:B6:B3:2C:16:08
ESP-NOW initialisedno MAC address to transmit too
no MAC address to transmit too
From 10:91:A8:02:00:E8 Bytes received: 12
Send too 10:91:A8:02:00:E8 esp_now_send() returns ESP_OK
INCOMING READINGS
Temperature: 24.50 ºC
Humidity: 79.00 %
Pressure: 22.00 hPa

Last Packet Send Status:	Delivery Success
From 10:91:A8:02:00:E8 Bytes received: 12
Send too 10:91:A8:02:00:E8 esp_now_send() returns ESP_OK
INCOMING READINGS
Temperature: 25.50 ºC
Humidity: 80.00 %
Pressure: 23.00 hPa

Last Packet Send Status:	Delivery Success
From 10:91:A8:02:00:E8 Bytes received: 12
Send too 10:91:A8:02:00:E8 esp_now_send() returns ESP_OK
INCOMING READINGS
Temperature: 26.50 ºC
Humidity: 81.00 %
Pressure: 24.00 hPa

Last Packet Send Status:	Delivery Success
From 10:91:A8:02:00:E8 Bytes received: 12
Send too 10:91:A8:02:00:E8 esp_now_send() returns ESP_OK
INCOMING READINGS
Temperature: 27.50 ºC
Humidity: 82.00 %
Pressure: 25.00 hPa

Last Packet Send Status:	Delivery Success
From 10:91:A8:02:00:E8 Bytes received: 12
Send too 10:91:A8:02:00:E8 esp_now_send() returns ESP_OK
INCOMING READINGS
Temperature: 28.50 ºC
Humidity: 83.00 %
Pressure: 26.00 hPa

Last Packet Send Status:	Delivery Success
From 10:91:A8:02:00:E8 Bytes received: 12
Send too 10:91:A8:02:00:E8 esp_now_send() returns ESP_OK
INCOMING READINGS
Temperature: 29.50 ºC
Humidity: 84.00 %
Pressure: 27.00 hPa

Last Packet Send Status:	Delivery Success
From 10:91:A8:02:00:E8 Bytes received: 12
Send too 10:91:A8:02:00:E8 esp_now_send() returns ESP_OK
INCOMING READINGS
Temperature: 30.50 ºC
Humidity: 85.00 %
Pressure: 28.00 hPa
initially test the transmitter using the broadcast address 0xff, 0xff, 0xff, 0xff, 0xff, 0xff then try the receiver MAC address

Re: ESP-32-C3 0.42 OLED ESP-NOW Wifi PWM

Posted: Mon Jul 28, 2025 11:11 am
by Jateu_01
horace99 thank you for replying. Yes I've checked all of these out. However I'm still struggling. I have asked other for help but it's not worked out. With my inability to comprehend at a good rate it's causing issues. So I used AI to help come up with a code but it's not working and a bit of a mess.

Many thanks

Re: ESP-32-C3 0.42 OLED ESP-NOW Wifi PWM

Posted: Tue Jul 29, 2025 6:05 am
by horace99
did you try the code in my previous post which worked on a ESP32-C3-MINI-1 ?
did it compile, link and upload OK? if not what errors did you get?
did it work? if not what was the serial monitor output?
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