1

I'm using an ESP32 WROOM board to capture some data in the field and send it over using arduino json. However, the complete process of sending and receiving confirmation takes up around 12 seconds and my ESP is frozen in that time. As a result, I lose the data in that time window. Is there a way to reduce the upload time of the ESP or maybe continue taking data while it is uploading?

Here is my data sending code for reference.

jsonBuffer.clear();
JsonObject &rootObject = jsonBuffer.createObject();
JsonObject &dataObject = rootObject.createNestedObject("data");
JsonArray &X1dataObject = dataObject.createNestedArray("X1");
JsonArray &Y1dataObject = dataObject.createNestedArray("Y1");
JsonArray &Z1dataObject = dataObject.createNestedArray("Z1");

if (wifiMulti.run() == WL_CONNECTED) {
  Serial.println("");
  Serial.println("WiFi connected");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
}


if (send_flag) {
  send_flag = false;
  int connection_iterator = 0;
  int connection_iterator2 = 0;
  for (int iterator = 0; iterator < SAMPLE_SIZE; iterator++) {
    X1dataObject.add(X1dataArray[iterator]);
    Y1dataObject.add(Y1dataArray[iterator]);
    Z1dataObject.add(Z1dataArray[iterator]);
  }

  rootObject["coreid"] = String(low, HEX) + String(high, HEX);
  //rootObject["coreid_high"] = String(high, HEX);
  rootObject["sample_time"] = int(time_taken);
  rootObject["firmware_version"] = FIRMWARE_UPDATE_VERSION;
  rootObject.prettyPrintTo(Serial);
  Serial.print("connecting to ");
  Serial.println(host);
  while ((!client.connect(host, httpsPort)) && !setup_mode) {
    connection_iterator++;
    Serial.println("connection failed! Retrying..");
    digitalWrite(LED2, HIGH);
    delay(5000);
    digitalWrite(LED2, LOW);
    delay(5000);
    if (connection_iterator >= 10)
      ESP.restart();
  }
  if (client.verify(fingerprint, host)) {
    Serial.println("certificate matches");
  } else {
    Serial.println("certificate doesn't match");
  }
  digitalWrite(LED_BUILTIN, HIGH);
  Serial.print("requesting URL: ");
  Serial.println(url);
  client.println(String("POST ") + url + " HTTP/1.0");
  client.println(String("Host: ") + host);
  client.println("Cache-Control: no-cache");
  client.println("Content-Type: application/json");
  client.print("Content-Length: ");
  client.println(rootObject.measureLength());
  client.println();
  //rootObject.printTo(client);
  Serial.println("NUMBER OF INTERRUPTS:");
  Serial.println(interruptCounter);
  Serial.println("request sent");
  while ((client.connected()) && !setup_mode) {
    connection_iterator2++;

    String line = client.readStringUntil('\n');
    if (line == "\r") {
      Serial.println("headers received");
      break;
    }
    Serial.println("Waiting for response");
    digitalWrite(LED2, HIGH);
    delay(1000);
    digitalWrite(LED2, LOW);
    delay(1000);
    if (connection_iterator2 >= 20)
      break;

  }
  String line = client.readStringUntil('\n');
  if (line.startsWith("{")) {
    Serial.println("esp8266/Arduino CI successfull!");
  } else {
    Serial.println("esp8266/Arduino CI has failed");
  }
  Serial.println("reply was:");
  Serial.println("==========");
  Serial.println(line);
  Serial.println("==========");
  Serial.println("closing connection");
  digitalWrite(LED_BUILTIN, LOW);
  // readRegister(INT_SOURCE, 1, &dummy_read);
}
  • In general, you would need to examine, in detail, which individual steps are taking the most time and try to find out how to reduce that. 12 seconds is enormous for sending an HTTP request and getting a reply, and the delay might be in the ESP32 code, might be in the website receiving the data, etc. Find out where most of the time is wasted and focus efforts there. (I am assuming sending data is an HTTP POST or GET, as json is not a protocol, but a structured text format.) – jose can u c Apr 16 at 13:46
  • you send it as many small writes? github.com/jandrassy/StreamLib/blob/master/README.md – Juraj Apr 16 at 14:21
  • JSON can be very verbose. It might be easier to send a regular GET request with a few data-variable in the query string. – Gerben Apr 16 at 16:07
  • esp32 is dual core. you can send on one core while the other continues to capture data. it is a bit complicated to get going, but works well. Aside from that, 12 seconds seems too long, maybe you should post some code here and we might be able to speed that up. – dandavis Apr 16 at 19:08
  • How big is this data? 12 seconds on the lowest connection speed - say 1mbit is, and taking into account some overheads, would be over 1megabytes of data - are you really sending that much? – Jaromanda X Apr 17 at 1:43

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.