Simple code snippet for talking to Serial devices - in this case a SIM7600E-H

SerialPassthrough.ino

#include <SoftwareSerial.h>
SoftwareSerial mySerial(8, 9);

void setup()
{
  delay(500);
  Serial.begin(115200);
  mySerial.begin(115200);  // use this line on a new module using 115200 baud by default
  //mySerial.begin(19200); // after setting the baud rate to 19200, we use this speed for mySerial
  pinMode(13, OUTPUT);
  delay(1000);
}

int counter = 0;

void loop()
{
  /* send everything received from the hardware uart to usb serial & vv */
  if (Serial.available() > 0) {
    Serial.print(">");
    delay(100);
    while ( Serial.available() ) {
      char ch = Serial.read();
      Serial.print(ch);
      mySerial.print(ch);
    }
  }

  if (mySerial.available() > 0) {
    Serial.print(":");
    delay(10);
    while ( mySerial.available() ) {
      digitalWrite(13, HIGH);
      char ch = mySerial.read();
      if ( ch ) {
        Serial.print(ch);
      }
    }
  } else {
    digitalWrite(13, LOW);
  }
}