Arduino + Modbus + MasterScada

I decided to create an alliance between arduino and Master Scada.

Why Master Scada? I will answer: Master Scada works through its own OPC server with a lot of settings, which allows you to have a good look at the process of polling channels (well, it's free for 32 channels).

For the test, I used two HC-04 ultrasonic rangefinders and the arduino uno board.
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Transmission carried out by modbus protocol.

To use the SimpleModbusSlaveV9 library in arduino, you need to install it first.

Sketch embedded in arduino:

// connect the library
#include <SimpleModbusSlave.h>
// declare variables
#define echoPin 2
#define trigPin 3
#define echoPin1 4
#define trigPin1 5

enum
{
ADC_VAL,
PWM_VAL,
HOLDING_REGS_SIZE = 4 // enter the number of channels

};

unsigned int holdingRegs [HOLDING_REGS_SIZE];

void setup ()
{

modbus_configure (& Serial, 115200, SERIAL_8N2, 1, 2, HOLDING_REGS_SIZE, holdingRegs); // enter the polling speed

modbus_update_comms (115200, SERIAL_8N2, 1);

// for ultrasound sensors

pinMode (trigPin, OUTPUT);
pinMode (echoPin, INPUT);
pinMode (trigPin1, OUTPUT);
pinMode (echoPin1, INPUT);
}

void loop ()
{
int duration, cm;

digitalWrite (trigPin, LOW);
delayMicroseconds (2);
digitalWrite (trigPin, HIGH);
delayMicroseconds (10);
digitalWrite (trigPin, LOW);
duration = pulseIn (echoPin, HIGH);
cm = duration / 58;

int duration1, cm1;
digitalWrite (trigPin1, LOW);
delayMicroseconds (2);
digitalWrite (trigPin1, HIGH);
delayMicroseconds (10);
digitalWrite (trigPin1, LOW);
duration1 = pulseIn (echoPin1, HIGH);
cm1 = duration1 / 58;
delay (100);


// Received values ​​are passed to OPC
modbus_update ();
holdingRegs [1] = cm1; // address 1
holdingRegs [2] = cm; // address 2
holdingRegs [3] = cm; // address 2


}

Next, configure the OPC. Select the port number and polling rate:



Create a device set the response time and the polling period:



Add Tags, for each parameter has its own tag. Enter in the column the value corresponding to the holdingRegs []:



And run:



Now move on to setting up MasterScada.

We connect the OPC server with the scud to draw the mnemonic scheme for visualization:



And run:



No failures were found; in the future, connecting sensors with a current output of 4-20 mA and using the arduino platform as a module for data collection and display at small objects.

If anyone is interested I can describe the exchange of arduino + Delphi