Receiving garbage value when sending a Json object from Arduino Uno to NodeMCU using SoftwareSerial

Question

I am trying to send a Json Object from Arduino UNO to NodeMCU using SoftwareSerial. I am using Arduino IDE. I am getting garbage value on Serial monitor of NodeMCU. Tried it with different garbage values, couldn't receive data from Arduino UNO. Below is the code. PLease help. Thank you in advance. I haven't made a common ground. I have referred this webpage here.

Arduino UNO code:

 #include <SoftwareSerial.h>
 #include <ArduinoJson.h>
 SoftwareSerial s(5,6);
 void setup() {
 s.begin(9600);
 }
 void loop() {
 StaticJsonBuffer<1000> jsonBuffer;
 JsonObject& root = jsonBuffer.createObject();
 root["data1"] = 100;
 root["data2"] = 200;
 if(s.available()>0)
 {
 root.printTo(s);
 }
 }

NodeMCU code:

 #include <SoftwareSerial.h>
 SoftwareSerial s(D6,D5);
 #include <ArduinoJson.h>
 void setup() {
 // Initialize Serial port
 Serial.begin(9600);
 s.begin(9600);
 while (!Serial) continue;
 }
 void loop() {
 StaticJsonBuffer<1000> jsonBuffer;
 JsonObject& root = jsonBuffer.parseObject(s);
 if (root == JsonObject::invalid())
 return;
 Serial.println("JSON received and parsed");
 root.prettyPrintTo(Serial);
 Serial.print("Data 1 ");
 Serial.println("");
 int data1=root["data1"];
 Serial.print(data1);
 Serial.print(" Data 2 ");
 int data2=root["data2"];
 Serial.print(data2);
 Serial.println("");
 Serial.println("---------------------xxxxx--------------------");
 }

• Majenko: I haven't made a common ground. -- they maybe you should? majenko.co.uk/blog/importance-sharing-grounds
• Muskan Chotrani: I tried making common ground too, same result

Answer 1

The problem with ArduinoJson.h is that it doesn't ensure robust and reliable transfer over UART serial.

Instead, you should use SerialTransfer.h to automatically packetize and parse your data for inter-Arduino communication without the headace.The library is installable through the Arduino IDE and includes many examples.

Here are the library's features:

This library:

• can be downloaded via the Arduino IDE's Libraries Manager (search "SerialTransfer.h")
• works with "software-serial" libraries
• is non blocking
• uses packet delimiters
• uses consistent overhead byte stuffing
• uses CRC-8 (Polynomial 0x9B with lookup table)
• allows the use of dynamically sized packets (packets can have payload lengths anywhere from 1 to 254 bytes)
• can transfer bytes, ints, floats, and even structs!!

Example TX Arduino Sketch:

#include "SerialTransfer.h"
SerialTransfer myTransfer;
void setup()
{
 Serial.begin(115200);
 Serial1.begin(115200);
 myTransfer.begin(Serial1);
}
void loop()
{
 char buff[] = "hi";
 myTransfer.txObj(buff, sizeof(buff));
 myTransfer.sendData(sizeof(buff));
 delay(100);
}

Example RX Arduino Sketch:

#include "SerialTransfer.h"
SerialTransfer myTransfer;
void setup()
{
 Serial.begin(115200);
 Serial1.begin(115200);
 myTransfer.begin(Serial1);
}
void loop()
{
 if(myTransfer.available())
 {
  char buff[40];
  
  myTransfer.rxObj(buff, sizeof(buff));
  
  Serial.println("New Data: ");
  Serial.write(buff, sizeof(buff));
  Serial.println();
 }
 else if(myTransfer.status < 0)
 {
  Serial.print("ERROR: ");
  if(myTransfer.status == -1)
   Serial.println(F("CRC_ERROR"));
  else if(myTransfer.status == -2)
   Serial.println(F("PAYLOAD_ERROR"));
  else if(myTransfer.status == -3)
   Serial.println(F("STOP_BYTE_ERROR"));
 }
}

• Muskan Chotrani: Thank you so much. It solved my problem. The transmission is proper now.