On older Liebert PDUs, UPS and other equipment may have a communications card called the OpenComms NIC (OpenComms Network Interface Card).
This card preceded the Liebert IS-WEB and IS-UNITY-DP communication cards found in newer hardware.
The OpenComms Network Communications Card (OCNIC) has an RS232 port for configuration.
An ethernet port for a web interface and SNMP data.
Lastly, an RS485 port that supports Modbus RTU communications for remote monitoring.
To configure the RS485 port for Modbus data, you must access the RS232 port to configure it.
You will need the following to set up the Modbus communications for the RS485 port.
Terminal Emulation software, such as HyperTerminal, Putty that supports VT100.
USB-RS232 adapter to plug into your laptop
Null-Modem serial cable
Connect the USB-RS232 adapter to your laptop and verify the COM port number used by the Device Manager.
Connect the Null Modem serial cable to the USB adapter and the other end to the RS232 (DB9) port on the OpenComms NIC.
Open your Terminal Emulation software and configure the following information.
- The COM port is used for the serial connection.
- Baud: 9600
- Parity: None
- Stop Bits: 1
- Flow Control: None
Once connected, click the enter key, or press the ESC key. You should see a menu of options.
- Select option # 3
- The RS485 Settings Menu should show.
- Option 1: Enabled Application, 1 = None; 2 = Modbus Server.
- Option 2: Control, Enable Modbus Control [y/n].
- Option 3: Server ID, Enter the server ID (1 – 255).
- Option 4: Communications Rate, 1 = 9600; 2 = 19200; 3 = 38400.
- Press the ESC key to return to the main menu.
- Press x for Exit and save changes
Once the card has rebooted, it takes about 20 – 30 seconds to complete.
Test the Modbus RTU communications RS485 port to confirm you have data.
Modbus information is based on the Liebert IGMnet protocol and depends on your equipment.
The older Liebert PDU we worked on was a PPA225 unit using the IGMnet PM2 modbus registers.
Menu Options
Main Menu
1: System Information
2: IP Network Settings
3: 485 Network Settings
4: Factory Settings
5: Firmware Updates
6: Quit and abort changes
7: Exit and Save
System Information
1: Name
2: Contact
3: Location
4: Description
IP Network Settings Menu
1: Boot/IP Settings
2: SNMP Communications
3: Web Server
4: Telnet Server
5: SNTP Configuration
6: Change Username/Password
485 Network Settings Menu
1: Enabled Application
1 = None
2 = Modbus Server
2: Control
Enable Modbus Control [y/n]
3: Server ID
Enter the server ID (1 – 255)
4: Communications Rate
1 = 9600
2 = 19200
3 = 38400