UNO Code

#include <SoftwareSerial.h>
#include <String.h>
SoftwareSerial toNode(2,3); // (Rx, Tx)

int sensorPin = A0;
int sensorValue;

void setup() {
 Serial.begin(9600);
 toNode.begin(115200);

 pinMode(9, OUTPUT);
 pinMode(10, OUTPUT);
 pinMode(8, OUTPUT);
}

void loop() {

 sensorValue = analogRead(sensorPin);
 Serial.println("Analog Value : ");
 Serial.println(sensorValue);

 if (sensorValue<300) {
 digitalWrite(10, HIGH);
 digitalWrite(9, LOW);
 digitalWrite(8, LOW);
 parseJson(sensorValue);
 }
 else if(sensorValue>300 && sensorValue<450){
 digitalWrite(9, HIGH);
 digitalWrite(8, LOW);
 digitalWrite(10, LOW);
 parseJson(sensorValue);
 }
 else if(sensorValue < 300)
 {
 digitalWrite(8, HIGH);
 digitalWrite(9, LOW);
 digitalWrite(10, LOW);
 parseJson(sensorValue);
 }

 delay(1000);
}

void parseJson(int criticidade) {
   String njs;
   njs = String(criticidade);
   toNode.println(njs);
}