max OPC items could be used ?

osamaafifi · April 15, 2020, 12:03am

Actually thats my first time to post here.
i was trying to communicate with my arduino uno using OPC.
i have a problem as below:
first, I need to establish 100 items (to be used and read by SCADA system (wonderware intouch) ) from arduino, i looked in the internet and used the available examples in library. and i succeed to establish and read/write on arduino pins
till now every thing is OK
i tried to increase the OPC items, it worked fine also till i reached approx. 50 items, after that the OPC explorer or web server couldnt communicate with my arduino.

this is my code (which is just a modification on library examples for illustration)

/*
 * A generic sketch for use with the Arduino OPC or Visual OPC Builder from www.st4makers.com
 */
#include <OPC.h>
#include <Bridge.h>
#include <Ethernet.h>
#include <SPI.h>

/*
 * Declaring the OPC object
 */
OPCEthernet myArduinoUno;

/*
 * MAC address from Ethernet shield sticker under board
 */
byte mac[] = { 0x90, 0xA2, 0xDA, 0x0E, 0xAD, 0x8D };

/*
 * Set your network configuration
 */
IPAddress ip(192, 168, 1, 25);
IPAddress gateway(192,168,1,2);
IPAddress dns_server(192,168,1,1);
IPAddress subnet(255,255,255,0);

/*
 * Server listen port
 */
const int listen_port = 80;

opcOperation digital_status_input[61], analog_status_input[6];

bool readwrite_digital(const char *itemID, const opcOperation opcOP, const bool value)
{
  byte port;
  
  port = atoi(&itemID[1]);

  if (opcOP == opc_opwrite) {
    if (digital_status_input[port] == opc_opread) {
      digital_status_input[port] = opc_opwrite;
    //  pinMode(port,OUTPUT);
    }
      
    digitalWrite(port,value);  
  }
  else
  {
    if (digital_status_input[port] == opc_opwrite) {
      digital_status_input[port] = opc_opread;
     // pinMode(port,INPUT);
    } 

    return digitalRead(port); 
  }  

}

int readwrite_analog(const char *itemID, const opcOperation opcOP, const int value) {
  byte port;
  
  port = atoi(&itemID[1]);

  if (opcOP == opc_opwrite) {
    if (analog_status_input[port] == opc_opread) {
      analog_status_input[port] = opc_opwrite;
   //   pinMode(port,OUTPUT);   
    }
     
    analogWrite(port,value);  
  }
  else
  {
    if (analog_status_input[port] == opc_opwrite) {
      analog_status_input[port] = opc_opread;
      //pinMode(port,INPUT);   
    } 

    return analogRead(port); 
  }  

}

void setup() {
  byte k;

  for (k=0;k<46;k++) digital_status_input[k] = opc_opread; 
  for (k=0;k<5;k++)  analog_status_input[k] = opc_opread; 
  
  /*
   * OPC Object initialization
   */
  myArduinoUno.setup(listen_port,mac,ip); 

  myArduinoUno.addItem("D0",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D1",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D2",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D3",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D4",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D5",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D6",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D7",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D8",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D9",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D10",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D11",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D12",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D13",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D14",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D15",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D16",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D17",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D18",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D19",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D20",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D21",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D22",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D23",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D24",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D25",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D26",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D27",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D28",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D29",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D30",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D31",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D32",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D33",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D34",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D35",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D36",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D37",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D38",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D39",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D40",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D41",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D42",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D43",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D44",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D45",opc_readwrite, opc_bool, readwrite_digital);

  
  myArduinoUno.addItem("A0",opc_readwrite, opc_int, readwrite_analog);
  myArduinoUno.addItem("A1",opc_readwrite, opc_int, readwrite_analog);
  myArduinoUno.addItem("A2",opc_readwrite, opc_int, readwrite_analog);
  myArduinoUno.addItem("A3",opc_readwrite, opc_int, readwrite_analog);
  myArduinoUno.addItem("A4",opc_readwrite, opc_int, readwrite_analog);
  myArduinoUno.addItem("A5",opc_readwrite, opc_int, readwrite_analog);    
}

void loop() {
  myArduinoUno.processOPCCommands();
}

and this is working fine, as attached photo

when i try to increase the items as below:

/// added to the above code
  myArduinoUno.addItem("D45",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D46",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D47",opc_readwrite, opc_bool, readwrite_digital);
 myArduinoUno.addItem("D48",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D49",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D50",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D51",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D52",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D53",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D54",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D55",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D56",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D57",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D58",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D59",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("D60",opc_readwrite, opc_bool, readwrite_digital);
  myArduinoUno.addItem("A5",opc_readwrite, opc_int, readwrite_analog);    
}

void loop() {
  myArduinoUno.processOPCCommands();
}

the OPC server couldnt start or get items as attached photo

so, my question why this happened ? is there any limitations for items quantities ?

Thanks in advance

blh64 · April 15, 2020, 2:56am

How many digital pins do you have on your Arduino Uno? I've only got 13 on mine.

Adding all those items requires memory. You Arduino is not your PC with megabytes of memory so I'm guessing you are running out.

osamaafifi · April 15, 2020, 8:28am

I know that i have 15 pins as DIO
I modified the example code just for illustration
I was talking about creating opc items limitations
In my project i have a different code and i am using shift registers.

osamaafifi · April 15, 2020, 1:04pm

The strange thing that when i used Serial opc server, it reached approx. 70 and then couldnt create more items. Although in both cases (serial and eathernet) the memory is enough and not consumed (as i am not creating any variables)

blh64 · April 15, 2020, 4:50pm

Every time you call .addItem() you most certainly are consuming memory. The Ethernet library takes up memory as well so it and probably a fair bit more than the Serial library so you have less memory to start with.

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max OPC items could be used ?

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