Arduino MEGA copy / atmega 2560 serial receive pins

Official Hardware Mega Mega 2560
1

Hello I bought a Arduino MEGA from AliExpress.

It is a bit more complex than the UNO I'm used to.
Anyway I got it working and can run scripts on it.

I start playing around with the HC-12 wireless module.

What I can't understand is why it's only some of pins that can receive serial data from the HC-12.

Pins I can get working:
10, 11, 12, 13, 50, 51, 52, 53.

Pins I can't get working:
0, to 9 and 14 to 21

The rest I haven't tested.

I can send serial data from almost all pins it seems.

Is it correct observed or is it faulty?

2

Show us your code.

3 
//HC-12 messenger send/receive
//autor Tom Heylen tomtomheylen.com

#include <SoftwareSerial.h>

SoftwareSerial mySerial(2, 3); //RX, TX

void setup() {
  Serial.begin(9600);
  mySerial.begin(9600);
}

void loop() {
  
  
  if(Serial.available() > 0){//Read from serial monitor and send over HC-12
    String input = Serial.readString();
    mySerial.println(input);    
  }
 
  if(mySerial.available() > 1){//Read from HC-12 and send to serial monitor
    String input = mySerial.readString();
    Serial.println(input);    
  }
  delay(20);
}
4

It works fine on my arduino Nano

5

Hi, @henrik9979

The Mega has 4 hardware serial ports, why are you using softwareserial?

image
image1283×260 21.1 KB

Tom... :grinning: :+1: :coffee: :australia:

6

Because I haven't used a MEGA or a HC-12 transmitter before and is starting to learn how to use them.

Following YouTube videos like this. https://youtu.be/DGRPqeacJns?si=3UjhWoV-vYq2o_Av

7

The SoftwareSerial library webpage has the following note:

8

Okay it almost fit the description for my board.
Pin 14 and 15 won't receive data however.

But however it seems like I can get it to work with Pin0 if I connect it directly to the pin1 on the Arduino Nano, without using the HC-12

Screenshot_20231126-023043
Screenshot_20231126-0230431080×1920 180 KB

Screenshot_20231126-023443
Screenshot_20231126-0234431080×1920 183 KB

9

The board in your photos isn't an Arduino MEGA (2560), but a hybrid board based around the MEGA2560 with the addition of an ESP8266 module.

You need to read the documentation as I believe that one of the hardware serial ports on the MEGA2560 is used to communicate with the ESP8266.

10

https://a.aliexpress.com/_mKuvW1E

It says:
USB converter CH340G connect to RX0/TX0 of ATmega2560
ESP8266 connect to RX3/TX3 of ATmega25

11

Please reread post #5, you shouldn't use SoftwareSerial on Mega, use HardwareSerial instead

So you can use TX1 RX1 or TX2 RX2 for HC-12

12

Then what should I change in the code to use hardware serial, also what are the differences?

13

Use Serial1 or Serial2 ( it depends on pins you connect to HC-12) instead of mySerial. Get rid anything related to SoftwareSerial from the code.

15

Like this?

Serial1; //RX, TX

void setup() {
  Serial.begin(9600);
  Serial1.begin(9600);
}

void loop() {
  
  
  if(Serial.available() > 0){//Read from serial monitor and send over HC-12
    String input = Serial.readString();
    Serial1.println(input);    
  }
 
  if(Serial1.available() > 1){//Read from HC-12 and send to serial monitor
    String input = Serial1.readString();
    Serial.println(input);    
  }
  delay(20);
}
16

The very first line

is not needed, like the Serial, Serial1 already defined in Arduino IDE

17

Just for curiosity, why do you use different condition for two serial ports?

18

I basically just followed the YouTube video I send post#6