#Hacer conexion modbus poll to plc how to#
#Hacer conexion modbus poll to plc update#

The ModbusSlave() instruction is placed between these two statements because it only needs to execute once at compile time rather than being executed during each scan. The instruction is added between the BeginProg and Scan statements. LetвЂ™s take a closer look at the ModbusSlave() instruction we added to the program code. 'Populate Modbus Registers ModbusRegisters(1) = PTemp ModbusRegisters(2) = batt_volt ModbusRegisters(3) = analog_meas 'Configure the datalogger as a Modbus Slave ModbusSlave (502,0,1,ModbusRegisters(),ModbusCoil,2) This is accomplished using the code below:

#Hacer conexion modbus poll to plc update#

To do this, we need to use the ModbusSlave() instruction, declare a variable array to hold our Modbus data, and then update that array with our measurements.

Therefore, we need to program our data logger to listen to Modbus polls on the appropriate communications port and to respond with our most current measured data. The CR1000 datalogger in our example is connected to a SCADA system using an NL121 Ethernet Interface. 'Measure the datalogger panel temperature In our example, the CR1000 is programmed to measure battery voltage, panel temperature, and an analog measurement in a simple program as shown below: You may remember our previous discussion about SCADA systems and Modbus from the вЂњWhy Modbus Matters: An IntroductionвЂќ blog article. WeвЂ™ll use a CR1000 datalogger connected to a SCADA system.

#Hacer conexion modbus poll to plc how to#

To better understand how this works, weвЂ™ll go through an example exercise to show the basic concepts of how to implement the Modbus protocol on a CR1000 datalogger.

Turning your data logger into a Modbus TCP/IP server is a great way to allow systems that use the Modbus protocol to have access to your live measurement data. This means that the data logger is configured to implement the Modbus communications protocol and listen for Modbus polls from a Modbus client, such as a SCADA (supervisory control and data acquisition) system. Did you know that you can turn your Campbell Scientific data logger into a Modbus TCP/IP server? Do you know why thatвЂ™s a good idea? Campbell Scientific data loggers are commonly used as Modbus server devices.