I'm having a BACnet hardware controller device which is having some points created in it.
I made a code which writes, gets and discovers points on a BACnet controller, but I need to use BACNet4J to create a new point with specific properties.

I'm working on a data acquisition system wchich should work on linux laptop and i am using Modbus4J and have implemented my own serial port wrapper which will by default ask for port-name(String) which is usually (/dev/ttyUSB1, /dev/ttyUSB2, etc)

But to my surprise the dev path to USB aren't constant and keeps changing in the order of connection.

when I connect two serial port converts to two USD ports the first connected ones take /dev/ttyUSB0 and the later /dev/ttyUSB1. This is an issue.

How is should have been done actually?

Hi,
I'm building a java modbus data acquisition system (using MODBUS4J), I've successfully communicated with the modbus device using its slave id, address, datatype.

But is there a way to just detect slaves, by just addressing slaves from 0-255 without specific register or coil addresses? So, that slaves with matching slaveId's respond.

@phildunlap thanks a lot.

@phildunlap OMG thanks, but how can we fix this?

wrapper.getInputStream is returning null.

I've tested this code to detect a Modbus device ( was discovered by a discovery software) connected to my computer.
but the code throw a null pointer Exception, can someone help me understand it.

public class MasterTest {
public static void main(String[] args) throws Exception {

	String commPortId = "/dev/ttyUSB0";
	int baudRate = 9600;
	int flowControlIn = 0;
	int flowControlOut = 0;
	int dataBits = 0;
	int stopBits = 0;
	int parity = 1;
	
	TestSerialPortWrapper wrapper = new TestSerialPortWrapper(commPortId, baudRate, flowControlIn, flowControlOut, dataBits, stopBits, parity);
    
    IpParameters ipParameters = new IpParameters();
    ipParameters.setHost("localhost");

    ModbusFactory modbusFactory = new ModbusFactory();

     ModbusMaster master = modbusFactory.createRtuMaster(wrapper);
    try {
        master.setTimeout(1000);
        master.setRetries(0);
        master.init();
        int slaveId = 2;
      BaseLocator<Number> locator = BaseLocator.holdingRegister(slaveId, 50, DataType.EIGHT_BYTE_INT_UNSIGNED);
        master.setValue(locator, 10000000);
        System.out.println(master.getValue(locator));
    }
    finally {
        master.destroy();
    }
}

I want to develop a JAVA code using MODBUS4J which should discover and read data from modbus controllers present in its network.

Is there a feature like autodiscovery in modbus like that of bacnet?

I have a doubt if my code should be a master or slave?

if master can a network have multiple masters? for network might have a plc or a master modbus controller.

if a slave can a slave communicate with a master to get all data?