RV50 as serial bridge


#1

Forgive me if I’m asking a question that’s been covered in the documentation. I’m in a pre-sales situation where I don’t have access to hardware to test. Also forgive my use of confusing terms, most of this is foreign technology to me.

We’re looking to install an RV50 at a remote site (LTE) with devices that are monitored via rs232/serial. The hardware and software is provided by TASC, we’re using siteVIEW 2.0.

Traditionally, we’re using a 900MHz RF network with GE MDS Orbit routers on both the monitored and the monitoring ends. They essentially extend the serial connection transparently. Unfortunately, we don’t have a reliable RF connection between the monitoring console and the remote site.

The software we’re using (siteVIEW 2.0) requires a serial port on the monitoring console (it’s a windows 7 PC).

The software vendor is telling us there should be a driver we can install on the Windows 7 PC that’ll connect to the RV50 via TCP/IP (the remote network will be routable over an IPSEC tunnel) essentially creating a virtual serial port.

I’ve been back and forth with Sierra pre-sales and I’ve reached a dead-end where they’re essentially telling me there’s no way to do what we want to do.

We’re willing to install hardware at both locations if required, again the end goal is to extend the rs232 serial connection over an IPSEC tunnel.

If anyone can point me in the right direction it’d be greatly appreciated.

Thanks in advance,
Ryan


#2

I would put a small single-board computer (SBC) running Linux at the remote end (e.g. a Raspberry Pi), plug its ethernet port into the RV50, and your serial equipment to its serial port. You will need some software on the SBC, but depending on your needs this could be as simple as executing a single socat command. Do you need to send serial data to the remote location, or only receive it?

The VPN tunnel can either be initiated by the SBC, or the RV50 itself.


#3

Thanks @JBodlander all of what you said makes sense to me. I’m going to confirm with another team as to whether traffic originates on both ends or just the remote site.

I feel I may have botched the question though, my understanding is that the RV50 has a DB9 serial connection already?

The hope would be to plug the remote sensors into the DB9 on the RV50, have it traverse the internet over IPSEC VPN which terminates at a central site. It’s the DB9 serial connection at the central site that’s required, our monitoring station only accepts serial interfaces.


#4

I feel I may have botched the question though, my understanding is that the RV50 has a DB9 serial connection already?

It does, but AFIK it is not a “host” (DTE) device but a “slave” (DCE); or in other words, the serial connection is for connecting a computer to the RV50 in order to control the functionality of the router and/or to use it as a modem (using good old Hayes “AT Commands”). It’s not unreasonable to think that one might be able to write a custom ALEOS application to run on the RV50 that would grant the serial port more flexibility, however if Sierra Wireless themselves say this is not possible then… well… it probably isn’t.


#5

This makes lots of sense, thanks again for your help @JBodlander. We’re going to go ahead and purchase one so we can get it in the lab for testing.


#6

Further to this, while I suspect you might be able to find a 3G/4G modem that has been designed for this exact purpose (serial port to TCP/IP over VPN), from some other manufacturer, having a small computer running a plain Linux flavour in your remote location is probably cheaper, and gives you a lot more flexibility/expandability. It would be trivial to expand the sensing capabilities, e.g. for temperature and intrusion monitoring. The Rapspberry Pi is very generously equipped in the I/O department, and the Raspbian Linux distro is basically Debian, which provides a staggering amount of free and open source software and utilities. As an example, here’s a screengrab from my own monitoring system’s environmental dashboard, which runs on a Raspberry Pi behind an RV50 connected to my VPN:

Edit: I know it looks like there’s a lot of duplication of measurements in the third column, but this is actually data pulled in from OpenWeatherMap, including six day weather forecast data. The second column shows actual weather data from my own sensors.


#7

This looks fantastic, thanks @JBodlander, once we get our hands on one of them I’ll post some updates here.

Thanks again for your help, very useful.