ESP32 Forum

Posted: **Mon Jan 11, 2021 12:42 am**

Hey guys been working with ESP32 for about a month because of a project i choose in my school and I'm having a hard time.
So the project is about a Strain Gauge sensor I'm getting data through an analog port of ESP32 and after some processing I'm sending these data on Android app to display, which I've developed through MIT app inventor.
The problem is that after every connection the first time I'm getting the correct data ONE time (as i want) but when i stop the request (but still connected) and then request the them again I'm getting the correct data 3-4 times. If I (as a client through Android) disconnect from the ESP32 and then connect again, I will get the correct data one time but every time I'm stopping the request and then requesting again the data show on android more and more times.
I've changed the MIT app inventor code and the Arduino main loop code many times but with no luck.

Thanks in advance!!
Here is the code for anyone interested.

Code: Select all

#include <BLEDevice.h>
#include <BLEUtils.h>
#include <BLEServer.h>

#define SERVICE_UUID        "4fafc201-1fb5-459e-8fcc-c5c9c331914b"
#define CHARACTERISTIC_UUID "beb5483e-36e1-4688-b7f5-ea07361b26a8"

  String analogSensor;
  int sentFlag = 0; //flag for the "sent" loop
  int i = 0;
  int s[100];
  int endOfStrikeFlag = 1;
  int beginStrike = 0;
  int maxStrike = 0;
  int strikeTime = 0;
  std::string androidtxt;
  BLECharacteristic *pCharacteristic;

float kilo (int x){
  float y = 0;
  if ((x >= 640) and (x < 695)){
    y = 2.5;
  }
  else if ((x >= 695) and (x < 730)){
    y = 5;
  }
  else if ((x >= 730) and (x < 800)){
    y = 7.5;
  }
  else if ((x >= 800) and (x < 845)){
    y = 10;
  }
  else if ((x >= 845) and (x < 880)){
    y = 12.5;
  }
  else if ((x >= 880) and (x < 950)){
    y = 15;
  }
  else if ((x >= 950) and (x < 1020)){
    y = 17.5;
  }
  else if (x >= 1020){
    y = 20;
  }
  else {
    y = 0;
  }
  return y;
}
void setup() {
  Serial.begin(115200);
  pinMode(LED_BUILTIN, OUTPUT);
  analogReadResolution(10);

  BLEDevice::init("ESP32");
  BLEServer *pServer = BLEDevice::createServer();
  BLEService *pService = pServer->createService(SERVICE_UUID);
  pCharacteristic = pService->createCharacteristic(
                                         CHARACTERISTIC_UUID,
                                         BLECharacteristic::PROPERTY_READ |
                                         BLECharacteristic::PROPERTY_WRITE  |
                                         BLECharacteristic::PROPERTY_NOTIFY  |
                                         BLECharacteristic::PROPERTY_INDICATE
                                       );

  //pCharacteristic->setCallbacks(new MyCallbacks());
  pCharacteristic->setValue("Hello World");
  pService->start();

  BLEAdvertising *pAdvertising = pServer->getAdvertising();
  pAdvertising->start();
  
}

void loop() {
  // main code running every 10ms
  delay(1);
  std::string androidtxt = pCharacteristic->getValue();
  
//Check if the signal frome the andoid is for power or speed or free practice
  if (androidtxt.find("pwrstrt") != -1) {
    strikeTime = 99;    //Power comsumes more time and less strikes
    sentFlag = 1; 
  }
  else if (androidtxt.find("spdstrt") != -1) {
    sentFlag = 2;
    strikeTime = 99;    //Speed consumes less time and more strikes
  }
  else if (androidtxt.find("frstrt") != -1) {
    sentFlag = 3;
    strikeTime = 99;    //Free training must have both speed and power, so strikes must be in the midle
  }
  //interupt measurement for FREE TRAINING
  else if (((androidtxt.find("pwrstp") != -1) or (androidtxt.find("spdstp") != -1) or (androidtxt.find("frstp") != -1)) and (sentFlag != 0)) {
    Serial.println("ANDROID DOES NOT WANT A VALUE");
    sentFlag = 0;
    digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
    delay(500);                       // wait for 500ms
    digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
    delay(500);                       //wait for 500ms
  }

  //Measure POWER
  if ((sentFlag == 1) or (sentFlag == 2) or (sentFlag == 3)) {
    delay(1);
    //Measure ONLY 1 strike
    beginStrike = analogRead(34);
    if (beginStrike >= 630){
      endOfStrikeFlag = 0;
    }
    while ((beginStrike >= 630) or (endOfStrikeFlag == 0)){
      // read the ongoing strike
      if (i >= 97){
        endOfStrikeFlag = 1;
        i = 0;
        break;
      }    
      s[i] = analogRead(34);
      if (maxStrike != s[i]){ 
        maxStrike = max(maxStrike, s[i]);   //get the max value on each iteration
      }
      s[i] = 0;                          //zeroing each cell of the array to use it in the next strike
      delay(1);
      i = i + 1;
      beginStrike = analogRead(34);
    }    
    if (maxStrike >= 630){    
      analogSensor = String(kilo(maxStrike)); 
      pCharacteristic->setValue(analogSensor.c_str());     //sent analogSensor value on android
      pCharacteristic->notify();
      Serial.println(maxStrike);
      Serial.println(maxStrike);
      Serial.println(maxStrike);
    }
    maxStrike = 0;
  }

}

Posted: **Mon Jan 11, 2021 9:50 pm**

Solved it!! Nothing wrong with the arduino code, just messed up the MIT appinventor code.

Posted: **Sun Jan 17, 2021 8:22 pm**

Why do you have delay after LED GPIO pin? It is somehow related led supply type and led forward voltage (https://911electronic.com/led-diode-con ... -tutorial/)

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