Accessing legacy device with RS232 over 4G Internet

Question

I have an old device, that's located in a place where I don't have an easily accessible data connection. What I do today is I drive to where this device is located and plug a db9 rs232 serial connector to this device and turn on a laptop that has this device old Win32 software to download the latest acquired data points, clean the memory of the device, and let it keep logging data points. In two weeks, I need to drive again and do all of this again.

I would like to connect to this device rs232 port remotely, ideally creating a virtual serial com port on the computer and run the software I usually run locally, remotely. This Win32 software can also be run on Wine if needed without problems.

When looking for remote access to rs232 serial ports, I could only find for connecting through WiFi or other local networks, but I would like to access through internet. If this can be achieved using Android devices, it's even better. Is there any solution available for this problem?

Answer 1

I've worked with RTU's (remote terminal units), this is a common requirement.

Maybe a simple modem RS232/4G is enough GTM201, I've used those in the past. Depending on your specific needs you'll need to check for devices which suits better.

I've also used a Robustel solution. I've used one similar to M1200.

Moxa could also have options.

You'll have to search for "serial gateways". Creating one with a RPi, USB 2 RS232 converter and 4G modem is also an option.

Answer 2

I'm not sure there is a 'standard' solution for this, even if it is trivial - because the number of such use cases is surely fairly limited.

Since the rs232 protocol must be somewhat open, you can maybe simplify the process. Take a standard 4G enabled dev board, add a 3v3 to 12v RS232 convertor, and write some code to talk to the data logger. Sampled data can then be pushed to whatever cloud service you need.

A slightly more 'standard' approach would be to just tunnel rs232 over a TCPIP port. I think you could assemble this out of standard parts, even if you need to go phone->usb ethernet->hub->rs232 breakout. This should allow you to keep the legacy software in the loop if it turns out to be impossible to reverse engineer the protocol.

Answer 3

There are commercially available RS232 serial over TCP/IP devices. These tend to run in one of two modes.

1. Single device mode. This uses a custom driver on the computer that creates a local virtual serial port that represents the remote device.
2. Two devices configured to talk to each other, in this mode you plug the computer into one device with a normal serial cable and the remote device into the other and they pass data between each other.

Given the software you want to use is on Windows95 the second option is probably the best solution as you might struggle to get hold of Window95 virtual serial port drivers these days.

You should be able to link one of the serial over IP devices to a 4g modem/router and with either a VPN or a fixed IP address SIM so you can access it remotely.