Arduino Mega 2560 Serial not working?

Projects Programming
1

Hi,

I have a Mega2560, i have just added a bluetooth module from Sparkfun: https://learn.sparkfun.com/tutorials/using-the-bluesmirf?_ga=1.218309661.584573556.1417027436
However I have done exactly as the tutorial shows however I am not receiving any data on the serial, this was true even before I added the bluetooth module. For example if i just upload a simply program with a line saying Serial.print etc i still do not have anything show up in the serial monitor. I also had a program which was supposed to read from the serial monitor however this also didnt work.

I was just wondering whether there is something simple I am missing out here?

Thanks in advance for any replies, Jack.

2

Hello and welcome :slight_smile:

Did you wire it correctly (RX to TX0-3, TX to RX0-3), bauds set correctly in serial monitor? And post your code.

3

kcajlliw:
For example if i just upload a simply program with a line saying Serial.print etc i still do not have anything show up in the serial monitor.

Is this happening when nothing is connected to any of the Mega pins? - in which case that is the first issue to resolve before doing anything about bluetooth.

On the other hand if it only happens when the bluetooth module is connected I suspect you are trying to use the Bluetooth with pins 0 and 1 (which belong to the USB connection) rather than connecting the bluetooth module to Serial1 which uses pins 18 and 19.

...R

4

Thanks for both of your replies. Sorry for the delay.

I have got the serial working properly now. The only problem is that the character being read from the bluetooth is always showing as 255.
I am using pins 0 and 1, should i change these to 18 and 19?

(Sorry I started another topic as I didnt realise they were related)

Thanks again, Jack.

5

Sorry, Here is the code:

#include <SoftwareSerial.h>
const int RX_PIN = 0;
const int TX_PIN = 1;
const int bluetoothVCC = 30;
const int bluetoothGND = 31;
SoftwareSerial serial(RX_PIN, TX_PIN);
char commandChar;
const int leftForward = 39;
const int leftReverse = 49;
const int rightForward = 27;
const int rightReverse = 45;
const int echopin = 24;
const int trigpin = 22;
bool lf = false;
bool lr = false;
bool rf = false;
bool rr = false;
int distpoint = 10;
int distance;
byte incomingByte;
void setup()
{
        Serial.begin(9600);
	pinMode(leftForward, OUTPUT);
	pinMode(rightForward, OUTPUT);
	pinMode(leftReverse, OUTPUT);
	pinMode(rightReverse, OUTPUT);
        pinMode(echopin, INPUT);
        pinMode(trigpin, OUTPUT);
        pinMode(bluetoothVCC, OUTPUT);
        pinMode(bluetoothGND, OUTPUT);
        digitalWrite(bluetoothVCC, HIGH);
        digitalWrite(bluetoothGND, LOW);
  //andomSeed(analogRead(0))
        
}

void loop()
{
        checkserial();
        distance = checkdistance();
        if (distance < 1)
        {
         //Something strange, lets ignore it.
        }
        else if (distance < distpoint){
          //TOO CLOSE, LETS REVERSE
            Serial.println("REVERSE");
            lf = false;
            rf = false;
            rr = true;
            lr = true;
            drive(); 
            delay(1500);
            //TURN RIGHT A SMIDGE
            rr = false;
            lr = false;
            lf = true;
            rf = false;
            drive(); 
            delay(500);
            rr = false;
            lr = false;
            lf = true;
            rf = true;
            drive();
        }  
        else {
           //Serial.println(distance);
           //Keep going forward
           drive();
        }      
      //KEEP IT SLOW  
       delay(500);
}

int checkdistance()
{
        digitalWrite(trigpin, LOW);
        delayMicroseconds(2);
        digitalWrite(trigpin, HIGH);
        delayMicroseconds(10);
        digitalWrite(trigpin, LOW);
        distance = pulseIn(echopin, HIGH);
        distance = distance/58;
        return distance;
  
}

void drive()
{
        if (lf){
        digitalWrite(leftForward, HIGH);
        digitalWrite(leftReverse, LOW);
        }
        else if(lr){
        digitalWrite(leftForward, LOW);
        digitalWrite(leftReverse, HIGH);
        }
        
        if (rf){
        digitalWrite(rightForward, HIGH);
        digitalWrite(rightReverse, LOW);
        }
        else if(rr){
        digitalWrite(rightForward, LOW);
        digitalWrite(rightReverse, HIGH);
        }
}

void checkserial()
{
  //IS THIS NEEDED?
  if (Serial.available() > 0) {
		// read the oldest byte in the serial buffer:
		incomingByte = Serial.read();
                Serial.println("DATA RECIEVED");
                Serial.println(incomingByte);
		//SELECT COMMAND FROM LIST
	                 if (incomingByte == 'Q'){ 
                          lf = true;
                          rf = false;
                          rr = false;
                          lr = false;
                         }
                        else if (incomingByte =='A'){
                          lf = false;
                          rf = false;
                          rr = false;
                          lr = true;
                        }
                        else if (incomingByte =='F'){ 
                          lf = true;
                          rf = true;
                          rr = false;
                          lr = false;
                        }
                        else if (incomingByte =='B'){ 
                          lf = false;
                          rf = false;
                          rr = true;
                          lr = true;
                        }
                        else if (incomingByte =='P'){
                          lf = false;
                          rf = true;
                          rr = false;
                          lr = false;
                        }
                        else if (incomingByte =='L'){
                          lf = false;
                          rf = false;
                          rr = true;
                          lr = false;
                        }
                        else if (incomingByte =='y'){
                          lf = true;
                          rf = false;
                          rr = true;
                          lr = false;
                        }
                        else if (incomingByte == 'T'){
                          lf = false;
                          rf = true;
                          rr = false;
                          lr = true;
                        }
			else 
                        {
                        Serial.println("Unknown Command");
                        }	
		}  
}
1 Like
6 
SoftwareSerial serial(RX_PIN, TX_PIN);

void checkserial()
{
  //IS THIS NEEDED?
  if (Serial.available() > 0) {

Serial1 is not the same as serial1 - c/c++ is case sensitive

And why are you using SoftwareSerial on a mega?

Mark

Oh - you also need a Serial1.begin()

M

7

Thanks for your reply.

Okay thanks. Sorry but just wondering why you have a symbol on the end of serial?

On the SoftwareSerial note - I am very novice with the arduino and this is what a tutorial suggested, but the tutorial was designed for an Arduino Uno. I am planning on moving the bluetooth system onto an Arduino uno when i have got it all working as it is going to be integrated into an electric car. Does the mega have an alternative?

Thanks again, Jack.

8

You can't use Software Serial on the same pins (0 and 1) that Hardware Serial uses. And on a Mega you can't use it on pins 14 to 19 either - they are used by the 3 other Hardware Serials. And with all those Hardware Serials there is no need to use Software Serial at all on a Mega.

...R