I'm JSON deserializing output from ESP8266 in my Arduino UNO, but when it fails (for some reason every time after it deserializes successfully) the program lags for few seconds and I don't want that to happen (at least not for a long time)

#include "SevSeg.h"
#include <ArduinoJson.h>
SevSeg sevseg; 

StaticJsonDocument<500> response;

String data;

void setup(){
  while (!Serial) {
     // wait for serial port to connect. Needed for native USB port only
  byte numDigits = 4;
  byte digitPins[] = {2, 3, 4, 5};
  byte segmentPins[] = {6, 7, 8, 9, 10, 11, 12, 13};
  bool resistorsOnSegments = false; // 'false' means resistors are on digit pins
  byte hardwareConfig = COMMON_ANODE; // See README.md for options
  bool updateWithDelays = false; // Default 'false' is Recommended
  bool leadingZeros = false; // Use 'true' if you'd like to keep the leading zeros
  bool disableDecPoint = false; // Use 'true' if your decimal point doesn't exist or isn't connected. Then, you only need to specify 7 segmentPins[]

  sevseg.begin(hardwareConfig, numDigits, digitPins, segmentPins, resistorsOnSegments,
  updateWithDelays, leadingZeros, disableDecPoint);


void loop(){

       if (Serial.available()) {
            const auto deser_err = deserializeJson(response, Serial);
            if (!deser_err) {
                if(response["type"] == "num"){
                String data = response["data"];

              Serial.print(F("Failed to deserialize, reason: \""));



The response

running  //runs everytime I turn on the arduino
21:43:03.797 -> {null
21:43:03.797 -> :null
21:43:03.797 -> ,null
21:43:03.797 -> :null
21:43:03.797 -> ,null
21:43:03.797 -> :Failed to deserialize, reason: "InvalidInput" // for some reason I have to send request 2 times because for the first time it always fails
21:43:03.797 -> 
Uove //correct data received
21:43:04.772 -> // this timestamp isn't right it is like 5 seconds after correct data
Failed to deserialize, reason: "EmptyInput"

What can I do for this not to happen for the first time or in a shorter duration?

I'd be really thankful for any answer.

  • so, the program does something different when it deserializes successfuly and you want to know why it does something different?
    – jsotola
    May 23 '21 at 20:16
  • Yes that too, I have a lot of questions about this weird behaviour
    – krystof18
    May 23 '21 at 20:20
  • What exactly are you sending over serial? The first character will be echoed back over Serial. It does not get used by the deseriallzation. That might be a problem depending on what you are sending.
    – chrisl
    May 23 '21 at 21:20
  • Do you know, what the timeout of the deserialization from serial is? That timeout is propably what takes so long.
    – chrisl
    May 23 '21 at 21:21
  • I don't know and i couldn't find it either, but I've noticed that the lower Serial.setTimeout the shorter the duration of waiting, but when u set it too low, it doesn't want to deserialize anything (the current 10s is minimum for it to work correctly)
    – krystof18
    May 23 '21 at 21:36

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