Easy Nextion Library Custom Protocol Explained

Now let’s see how we can assign commands to turn ON/OFF some relays.

Build the protocol **For more details on how it is built, see docs after the example**

To assign the commands to the proper tasks at MCU side, first we must read them

We read the commands with the NextionListen() function.
We don’t have to change or add anything in this function.
As the code is enough commented already, only a few words are enough.
• We read the Serial continually
• When the start marker <#> is identified we wait for number of bytes that we have specify with the <len> parameter.
• When we have all the expected bytes on Serial, we are sure that we found a command.
• We read and store the next byte that according to our protocol is the task ID or the command croup.

Second part is the assing of the commands

For that we call the readCommand() function and with a switch() command we assing them to tasks.
The readCommand() function is placed on the file readCustomCommands.cpp .
It is the only function on this file and we separate it from the main code in order to have easy access and simplicity for the modification and also to avoid mistakes and errors on the rest of library’s code.
readCustomCommands.cpp is the only file that we have to modify and add cases upon our needs.
Two cases is already predefined for future use.
Here is the code for the readcommand() function as an example on how we assign pages:

switch(_cmd1){  // _cmd is the variable where previous we have store the command ID
  case 'P':     /*or <case 0x50:>  If 'P' matches, we have the command group "Page". 
                 *The next byte is the page <Id> according to our protocol.
                 */
                // We set value of the clobal variable currentPageId egual to the reading byte.
    currentPageId = _serial->read();
    // break to Leave the case.
    break;
}

Step 1:
Prepare the Arduino code

On Arduino’s code we declare the pins for every Relay in an array:

const uint8_t TOTAL_RELAY = 6    // How many warning relays we use


const uint8_t relayPin[TOTAL_RELAY] = {2, 3, 4, 5, 6, 7};  // assigns the pin number for every relay
 /*
  * Declare that pin D2 is the pin that controls the Relay No0 (front lights)
  * Declare that pin D3 is the pin that controls the Relay No1 (Backyard lights)
  * Declare that pin D4 is the pin that controls the Relay No2 (swimming pool lights)
  * Declare that pin D5 is the pin that controls the Relay No3 (roofgarden lights)
  * Declare that pin D6 is the pin that controls the Relay No4 (adviser lights)
  * Declare that pin D7 is the pin that controls the Relay No5 (extra auxiliary lights)
  */

With a for() loop, setup the pins in the setup() function

 void setup(){
  // initialize relay outputs
  for(int i = 0; i < TOTAL_RELAY; i++){
    pinMode(relayPin[i], OUTPUT);     // Setting relay pin as OUTPUT
    digitalWrite(relayPin[i], LOW);  //Setting relay to LOW (off)
  }
}

Step 2:
Prepare the buttons on Nextion

Fron Nextion editor greate the buttons you need and on the Touhgt Release Event write the command:
printh 23 02 52 00 for the Relay No 0. printh 23 02 52 01 for Relay No1. For the Relay No 10, remember the HEX printh 23 02 52 0A

Step 3:
Modify the readCommand() function

Open the file readCustomCommands.cpp from the library's folder.
Go under the predefined case for future use and modify the code, like this:

 case 'R':  // or case 0x52:  If 'R' matches, we have the command group "Relays".
           // from the event of the button: < printh 23 02 52 xx > where xx the relay ID
  _tempRead = _serial->read(); // Read and Store the next byte to a local variable _tempRead

  digitalWrite(relayPin[_tempRead], !digitalRead(relayPin[_tempRead]));
  
  break;

The variable _tempRead must be created from the user.
Declare the variable outside the cases and the switch() command.
Prefer to create the variable above the switch() :

 void EasyNex::readCommand(){
  
  int _tempRead;
			
  switch(_cmd1){
    case 'P':
//...code continues

That’s all. Now every time a button is pressed, changes the stage off the assigned Relay from ON to OFF and the opposite.

Now, the full code:

//------------------------------------------------------------------------
//______________________ EasyNextionLibrary Configuration
//------------------------------------------------------------------------
#include "EasyNextionLibrary.h"

EasyNex myNex(Serial); // Create an object of EasyNex class with the name < myNex >
                       // Set as parameter the Serial you are going to use
//------------------------------------------------------------------------
//______________________ Relays Configuration
//------------------------------------------------------------------------

const uint8_t TOTAL_RELAY = 6    // How many warning relays we use


const uint8_t RelayPin[TOTAL_RELAY] = {2, 3, 4, 5, 6, 7};  // assigns the pin number for every relay
 /*
  * Declare that pin D2 is the pin that controls the Relay No0 (front lights)
  * Declare that pin D3 is the pin that controls the Relay No1 (Backyard lights)
  * Declare that pin D4 is the pin that controls the Relay No2 (swimming pool lights)
  * Declare that pin D5 is the pin that controls the Relay No3 (roofgarden lights)
  * Declare that pin D6 is the pin that controls the Relay No4 (adviser lights)
  * Declare that pin D7 is the pin that controls the Relay No5 (extra auxiliary lights)
  */
  
void setup(){
  // initialize relay outputs
  for(int i = 0; i < TOTAL_RELAY; i++){
    pinMode(relayPin[i], OUTPUT);     // Setting relay pin as OUTPUT
    digitalWrite(relayPin[i], LOW);  //Setting relay to LOW (off)
  }
  
  // Initialize EasynextionLibrary
  myNex.begin(9600); // Begin the object with a baud rate of 9600
                     // If no parameter was given in the begin(), the default baud rate of 9600 will be used 
}

void loop(){

  myNex.NextionListen(); // This function must be called repeatedly to response touch events
                         // from Nextion touch panel. Actually, you should place it in your loop function.
  
}
//*******************************************************************************************
// AND THIS MUST BE ADDED INSIDE THE switch() , replacing the 'X' future use case
// In the readCustomCommands.cpp file in library's  src  folder 
//*******************************************************************************************
/*
 case 'R':  // or case 0x52:  If 'R' matches, we have the command group "Relays".
           // from the event of the button: < printh 23 02 52 xx > where xx the relay ID
  _tempRead = _serial->read(); // Read and Store the next byte to a local variable _tempRead

  digitalWrite(relayPin[_tempRead], !digitalRead(relayPin[_tempRead]));
  
  break;
*/
//*******************************************************************************************
// The variable _tempRead must be created from the user.
// Declare the variable outside the cases and the switch() command.
// Prefer to create the variable above the switch()
//*******************************************************************************************