NL201 Network Link Interface
Serial to Ethernet Interface
Very low power
weather applications supported water applications supported energy applications supported gas flux and turbulence applications supported infrastructure applications supported soil applications supported


The NL201 is a serial-to-Ethernet interface that provides a wired Ethernet network connection to dataloggers, peripherals, and other serial devices. The NL201 supports sophisticated networking capabilities for PakBus devices and networks. Using a unique technique to bridge the Ethernet and CS I/O ports, the NL201 can provide direct access to the integrated IP functionality of some Campbell Scientific dataloggers. The NL201 can also act as a standard TCP serial server, serial client, Modbus TCP/IP gateway, and TLS proxy server for HTTPS and user-defined-port communication.

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Benefits and Features

  • Extremely low power consumption (650 mW)
  • Provides access to the native Internet protocol capabilities of the CR6, CR800, CR850, CR1000, and CR3000
  • Rugged serial-to-Ethernet server for networking devices and peripherals
  • PakBus routing and device initiated connections


Related Products

Technical Description

The NL201 connects to an Ethernet network using a 10Base-T/100Base-TX, full or half duplex, Ethernet interface. It has CS I/O and RS-232 ports for connecting a Campbell Scientific data logger, peripheral, Modbus RTU, or other serial-based device. A USB micro B connection is provided for on-site configuration using Device Configuration Utility software.

The NL201 can act as a PakBus router, TCP serial server, TCP serial client, Modbus TCP/IP gateway, and TLS proxy server for HTTPS and user-defined-port communications.

The NL201 also provides a unique mode that bridges the Ethernet and CS I/O ports. This allows access to the internal IP functionality of the CR6, CR800, CR850, CR1000, and CR3000 (for example, web page access, email, FTP). Adding an NL201 configured in this manner to a CR800 is analogous to adding an NL121 to a CR1000’s peripheral port. Adding an NL201 configured in this manner to a CR800 is analogous to adding an NL120 to a CR1000’s peripheral port.


Transmission Distance or Area Worldwide
Power Connector CS I/O port or DC barrel connector (not powered over USB)
Power Requirements 7 to 20 Vdc
CS I/O Port SDC 7, 8,10, or 11 (does not support ME)
RS-232 Port DTE
USB Port Micro-B
Ethernet Port 10Base-T and 100Base-TX (full and half duplex), Auto-MDIX, Auto-IP (APIPA), IPv4, IPv6, ICMP/Ping, ICMPv6/ Ping, TCP, DHCP Client, SLAAC, DNS Client, HTTPS Proxy, Telnet Server, TLS, PakBus, Mobus TCP/IP
Connections/Routes Supported
  • Supports 50 simultaneous TCP connections.
  • Up to 10 of the 50 TCP connections can be used for TLS.
  • PakBus Router supports 50 routes.
  • 15 Modbus Server Transactions (maximum)
Temperature Range
  • -25° to +50°C (standard)
  • -55° to +85°C (extended)
  • Device Configuration Utility over USB or Ethernet
  • Terminal menu over Telnet
  • Terminal menu over RS-232
Service Requirements Ethernet access
Dimensions 16 x 6.73 x 2.54 cm (6.3 x 2.65 x 1 in.)
Weight 177 g (6.3 oz)

Current Drain

Active 50 mA (@ 13 Vdc)
Forced Standby 2 mA (available when using Ethernet-to-CS I/O Bridge Mode)

Communication Rate

RS-232 Port 1200 bps to 115.2 kbps
CS I/O Port 9600 bps to 460.8 kbps
Ethernet 10/100 Mbps


RoHS Compliant
European Standards Meets requirements for a class B device under European Standards.
Application of Council Directive(s) 2004/108/EC
Standards to Which Conformity Is Declared EN61326-1;2013


Data Logger Considerations

Data Logger Serial Server PakBus Router Bridge Mode
CR200(X) Series
CR9000X *

data loggers


♣The CR300 connects to the NL201 using a 10873 serial that is not supplied with the CR300 or the NL201. The CR300-series dataloggers are not compatible with the bridge mode functionality in the NL201 interface.
* Although compatible, the CR9000X does not need an Ethernet interface because it has an on-board Ethernet port.
** It is possible to use an NL201 to connect to a mixed-array data logger (e.g., CR10, CR10X, CR23X, 21X, CR7) by using an SC32B between the data logger's CS I/O port and the NL201's RS-232 port.


NL200 / NL201 Firmware v.10.03 (571 KB) 04-09-2018

Current NL200 / NL201 firmware. Requires the Device Configuration Utility and a USB micro cable.

Note: When updating to OS 10.03 from OS 6 or previous, settings will be reinitialized to factory defaults. When updating to OS 10.03 from OS 7, settings will be retained.

View Revision History

FAQs for

Number of FAQs related to NL201: 12

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  1. After the OS has been sent, the NL201 will automatically be reset. There is no need to do it manually.

  2. No. A connection to the NL201 must be made to configure it for bridge mode. 

  3. Yes. An OS can be uploaded remotely over TCP/IP using our Device Configuration Utility (DevConfig) software. This method will not work, however, if the device has been configured to operate in bridge mode or if the device has not been configured with a valid IP address.

    To upload the OS over TCP/IP, do the following:

    1. Open DevConfig.
    2. Select NL200 from the list of device types.
    3. Click the Send OS tab.
    4. Follow the instructions listed in the “Download via Ethernet” section.
  4. Yes. We currently have, and continue to develop, a variety of products that are compatible with IPv6 networking. For example, the NL200/201 and NL240 can serve as IPv6 serial servers for our data loggers and communications peripherals. We anticipate IPv6 compatibility to be included in the CR800, CR850, CR1000, and CR3000 by mid-2014. 

  5. The NL201 and NL240 are available options.

  6. The NL121 plugs into the data logger and doesn't require an additional cable to work. The NL121 also doesn't take up much extra space. Because the NL121 has a faster interface to the data logger than the NL201 does, the NL121 communicates faster.

    The NL201 has to be mounted next to the data logger and requires a cable to connect to it. Also, the NL201 requires some additional configuration so that it will work with the data logger. For example, choices have to be made regarding how the NL201 is connected to the data logger. 

  7. The NL201 and NL240 are powered via the DC barrel connector and/or the CS I/O port. Sometimes, users who are using the network link
    interface as a serial terminal server, PakBus router, or Modbus gateway want to connect their devices via the CS I/O port while
    providing power only through the DC barrel connector and a 12 V source (such as a data logger SW12V output). In this scenario, a jumper
    inside the NL201 or NL240 can be removed, preventing the interfaces from always being powered by the CS I/O connections. For more
    information, refer to the instruction manual for the interface.

  8. The maximum recommended segment length (length of cable between the NL device and the Ethernet repeater, hub, switch, or router it is connected to) for 10Base-T and 100Base-Tx networks using CAT5e cable is 100 m. 

  9. Yes. For example, the NL115 allows the CR1000 to communicate over a local network or a dedicated Internet connection via TCP/IP. 

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