ESP8266 Community Forum

- Sun Jun 28, 2020 6:19 pm #87696 Hi,

I am a newbie, working on a project to send a sensor data from Master to slave using two ESP8266 boards with ESP-NOW protocol. I succeeded in sending the data and displaying on serial monitor using the code shared by https://www.youtube.com/watch?v=grWkbdN2A1Q&t=766s.

Now I am trying to include "Adafruit_SSD1306" 128x32 display to show the status of my master on slave device. Both master and slave codes are running fine without any errors, but while receiving the data on slave, the device is getting restarted and I found that the ESP8266 is restarting while executing the "SSD130" display command lines written in the function "SenderStatus()".

I could run the device by removing following lines (for example) from the function

if(atoi(value)==500)
{
Serial.println("Status 1 Ready");
/* display.clearDisplay (); // clear display
display.setCursor(10,13);
display.setTextSize(1);
display.setTextColor (WHITE);
display.print ("Status 1 Ready");
display.display ();//
delay(2000);
*/
}

And i tried to add the "SSD1306 allocation" commands again in the function just before "clear display" command, but no luck. How can I fix this to display the status on slave device using SSD1306.

Master:

Code: Select all#include <ESP8266WiFi.h>
#include<Wire.h>
extern "C" {
    #include <espnow.h>
}
// this is the MAC Address of the slave which receives the data
uint8_t mac[] = {0xDA, 0xBC, 0xC2, 0x11, 0x11, 0x11};
#define WIFI_CHANNEL 4


// must match the slave struct
struct __attribute__((packed))
DataStruct {
char text[15];
};

DataStruct Data;


//=======================================================================================

void setup() {
    Wire.begin(4,5);
    Serial.begin(115200);
    WiFi.mode(WIFI_STA); // Station mode for esp-now controller
    WiFi.disconnect();
    Serial.printf("This mac: %s, ", WiFi.macAddress().c_str());
    Serial.printf("slave mac: %02x%02x%02x%02x%02x%02x", mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
    Serial.printf(", channel: %i\n", WIFI_CHANNEL);
    if (esp_now_init() != 0)
    {
    Serial.println("*** ESP_Now initialization failed");
    }
    esp_now_set_self_role(ESP_NOW_ROLE_CONTROLLER);
    esp_now_add_peer(mac, ESP_NOW_ROLE_SLAVE, WIFI_CHANNEL, NULL, 0);
    strcpy(Data.text,"");
delay(2000);
 strcpy(Data.text,"500"); //status 1
 sendData();
delay(2000);
 strcpy(Data.text,"600"); //status 2
 sendData();
delay(2000);
 strcpy(Data.text,"700"); //status 3
 sendData();
delay(2000);
     strcpy(Data.text,"800"); //status 4
 sendData();
delay(2000);

Serial.println("Setup finished");
}

//=======================================================================================

void loop() {
 ReadSensor();
    sendData();
}

//============================================================================================
void ReadSensor()
{
  char S_text[10];
  double sensor=380.21; // dummy sensor value
  dtostrf(sensor, 3, 2, S_text);
  strcpy(Data.text,S_text);
}

void sendData()
   {
        uint8_t bs[sizeof(Data)];
        memcpy(bs, &Data, sizeof(Data));
        esp_now_send(NULL, bs, sizeof(Data));
        Serial.println(Data.text);
   }


Slave:

Code: Select all#include <ESP8266WiFi.h>

extern "C" {
    #include <espnow.h>
     #include <user_interface.h>
}
uint8_t mac[] = {0xDA, 0xBC, 0xC2, 0x11, 0x11, 0x11};

//==============Display=============
// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 32 // OLED display height, in pixels
#define OLED_RESET    -1 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

void initVariant() {
  WiFi.mode(WIFI_AP);
  wifi_set_macaddr(SOFTAP_IF, &mac[0]);
}

//==============

#define WIFI_CHANNEL 4

// must match the controller struct
struct __attribute__((packed))
DataStruct {
    char text[15];
};

DataStruct myData;
int8_t flag=0;
//==================================================================================

void setup() {
    Serial.begin(115200); Serial.println();
    Serial.println("Starting....");
    Serial.print("AP mac: "); Serial.println(WiFi.softAPmacAddress());
    Serial.print("STA mac: "); Serial.println(WiFi.macAddress());

//display
  Wire.begin(4,5);
// SSD1306_SWITCHCAPVCC = generate display voltage from 3.3V internally
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3C for 128x32
    Serial.println(F("SSD1306 allocation failed"));
    for(;;); // Don't proceed, loop forever
  }
 
  // Show initial display buffer contents on the screen --
  // the library initializes this with an Adafruit splash screen.
  delay(2000); // Pause for 2 seconds

 
  display.clearDisplay (); // clear display
  display.setCursor(20,13);
  display.setTextSize(1);
  display.setTextColor (WHITE);
  display.print ("Starting....");
  display.display ();//
  delay(2000);
 
 display.clearDisplay (); // clear display
 display.setCursor (12,8); // position the cursor
 display.setTextSize (2); // medium size font
 display.setTextColor (WHITE); // white is not default !
 display.print ("Hello");
  display.display ();//
  delay(2000);
 
  //ESP Initialize
    if (esp_now_init()!=0) {
        Serial.println("*** ESP_Now init failed");
        while(true) {};
    }

    esp_now_set_self_role(ESP_NOW_ROLE_SLAVE);
    esp_now_register_recv_cb(receiveCallBackFunction);
   Serial.println("End of setup - waiting for messages");
}

//=======================================================================================

void loop() {

}

//=======================================================================================

void receiveCallBackFunction(uint8_t *senderMac, uint8_t *incomingData, uint8_t len) {
    memcpy(&myData, incomingData, sizeof(myData));
   if(flag<=3)
    {
     SenderStatus();
    }
   Serial.println(myData.text);
}

void SenderStatus()
{
   
    char value[15];
    strcpy(value,myData.text);
    if(atoi(value)==500)
    {
      Serial.println("Status 1 Ready");
      display.clearDisplay (); // clear display  (restarting while executing these line)
      display.setCursor(10,13);
      display.setTextSize(1);
      display.setTextColor (WHITE);
      display.print ("Status 1 Ready");
      display.display ();//
      delay(2000);
    }
    else if(atoi(value)==600)
    {
      Serial.println("Status 2 Ready");
      display.clearDisplay (); // clear display
      display.setCursor(18,13);
      display.setTextSize(1);
      display.setTextColor (WHITE);
      display.print ("Status 2 Ready");
      display.display ();//
      delay(2000);
    }
    else if(atoi(value)==700)
    { 
      Serial.println("Status 3 Ready");
      display.clearDisplay (); // clear display
      display.setCursor(18,13);
      display.setTextSize(1);
      display.setTextColor (WHITE);
      display.print ("Status 3 Ready");
      display.display ();//
      delay(2000);
    }
    else if(atoi(value)==800)
    { 
      Serial.println("Status 4 Ready");
      display.clearDisplay (); // clear display
      display.setCursor(18,13);
      display.setTextSize(1);
      display.setTextColor (WHITE);
      display.print ("Status 4 Ready");
      display.display ();//
      delay(2000);
 
      Serial.println("Receiving Data");
      display.clearDisplay (); // clear display
      display.setCursor(18,13);
      display.setTextSize(1);
      display.setTextColor (WHITE);
      display.print ("Receiving Data");
      display.display ();//
    }
    flag++;
}


- Tue Jun 30, 2020 2:05 am #87706 I don't know this specific library but there are a lot that are not esp8266 compatible.
Most of them do have some wait or polling loops that do trigger the watchdog in the esp.
You'd have to identify these loops and spice them with yield() statements.
To be sure you have to log the serial mesages from the slave when it restarts.

- Wed Jul 01, 2020 5:58 am #87723 Hi All,

Finally i resolved the issue, the problem was stack overflow (RAM) while printing on screen since "Adafruit" library uses more ram space, nearly 1 to 1.5KB while printing. My code has a CHAR array as global variable which uses more RAM while running the code and ESP8266 was restarting while trying to print on screen using "Adafruit" library. So I replaced it with a U8g2 library which uses very less RAM space and can clear the memory by "clearBuffer()" command.

Thank you all for your help