The following are instructions to set up cellular communications between a computer and a remote serial port interface device, such as a CR1000 Datalogger. The Digi Connect WAN includes software called Real Port, which will create a virtual COM port on a local computer which is linked to the cellular modem located in the field. In this way, the software controlling the datalogger sees the datalogger as a local serial port device so long as the cellular modem is connected and powered on.
Cellular communications allow for access to data anywhere cellular service is available, utilizing standard cellular data packages. To be able to successfully set up a communications link, however, a basic understanding of how cellular data plans work is required. Any device on the internet is located by utilizing an IP address. An IP address is a characteristic string of numbers unique to a device on the internet. However, there are a limited number of IP addresses available and they are costly to own, and because not everyone is utilizing their cellular device at the same time, a cellular provider does not own as many IP addresses as they have customers. To make this work, the data plan provider utilizes dynamic IP addresses, which means that when you try to access the internet, you will be assigned a temporary IP address for your device for the duration of time you are using it. When you are done with it, it is released and can be assigned to another user. In addition, most cellular packages utilize a set of private IP addresses, which means that you cannot “dial in†they are only able to “dial out†into the internet.
This system works well in device initiated situations, where the device can dial the central server, ask for an IP adress and then continue to access the internet with this address. However, in the case of data collection, the communications is initiated by the computer collecting the data, and it needs to know how to find the device, the address of which is changing constantly.
In order to acheive this, the modem has support for a DNS hostname. A DNS hostname allows the device to dial the cellular provider, receive an IP address, and then register it under a constant hostname. For the snowstudy, http://snowstudy.dyndns.biz/ was used, it was registered at a free site at www.dyndns.com. Now, by pointing the browser to the DNS hostname of the device, it automatically retreives the current Dynamic IP address and can find the modem.
The second problem is to bypass the private IP address. In order to do this, a more expensive VPN (Virtual Private Networking) plan must be purchsed. This provides a dynamic public IP address.
The Digi Connect WAN modem can work seamlessly with the Cambell Scientific Datalogger utilizing the RealPort feature on the modem. This feature allows the serial port on the modem to act like a local serial port (COM 1-5 usually) on any computer which has the software installed. The software will dial the DNS hostname of the modem, and establish a virtual link with its serial port. The datalogger then operates as if it is attached to the local machine.
The modem should now be adressed to the DNS hostname. Disconnect the modem from the ethernet port on the computer, and direct the browser to the DNS hostname, the configuration screen should appear.
Now set up the realport configuration
Take note of the current IP address and the cellular number of the modem, for reference when dealing with the cell phone company.
If there is a communications issue, there is a method to check the operation of the serial port to narrow down the problem to the datalogger or the remote connection.
| License | CC-BY-SA-3.0 |
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| Cite as | R.Andrews (2011–2025). "Digi-Connect WAN modem for cellular connection of dataloggers". Appropedia. Retrieved October 3, 2026. |
