Sketch talks to Android via BLE on Serial2 but times out after 5 seconds when Serial cable disconnected or not present

Question

From an Android phone I am using the "Serial Bluetooth Terminal" app to communicate to an Arduino Mega 2560 with a Bluetooth Low Energy HM10 (Jaycar XC-4382) module connected via Serial2.

If the physical USB serial cable (Serial) is connected to Arduino the very simple sketch below works fine and runs continuously. When the cable is disconnected mid sketch or the power is cycle without the cable connected the sketch will run for about 5 seconds and then stop.

How can I prevent the sketch from timing out when the serial cable is disconnected?

int counter = 0;
void setup() 
{
 Serial2.begin(9600); 
}
void loop()
{
 Serial2.print(counter); Serial2.println();
 delay(1000);
 counter++;
}

• Juraj: how do you power it when disconnected from USB?
• Brett: 12V dc power supply plugged in to the mains

Answer 1

The workaround is to switch to using SoftwareSerial, see code below. Data is continuously sent via Bluetooth from Arduino Mega to Android with or without the usb cable connected.

#include <SoftwareSerial.h>
// Connections
// Arduino HM10
// MEGA
// ---- ----
// 3.3v VCC
// GND GND
// 12 RX
// 13 TX
SoftwareSerial bte(12,13); // RX, TX use (2,3) for UNO
int counter = 0;
void setup() { 
 // set the data rate for the SoftwareSerial port
 bte.begin(9600);
 bte.println(counter);
}
void loop() { // run over and over
 bte.println(counter);
 counter++;
 delay(1000);
}

• Juraj: he has a Mega with 4 hardware Serials