Forward USB Serial Data Without Host PC?

Looking for a product recommendation to directly connect 2 USB devices and eliminate the need for a host pc to forward USB serial data?

Device A outputs sensor data via USB serial connection.
Device B receives sensor data (originally created by device A).
Currently both device A and B are connected to a windows laptop running a tiny utility that forwards the com port serial data from device A to the com port for device B.

This works perfectly today, but in this application, having to dedicate a PC simply to forward serial data is cumbersome. Modifying either device A or B is not practical.

I suspect there may be an off the self hardware product that could forward the data, but when looking at potential solutions, it’s unclear to me which of them will accomplish my goal.

Can you offer any product recommendations?

Hi junk5949,

Welcome to the Tech Forum!

From your description, it sounds like both your USB sensor device (A) and your USB receiving device (B) are “USB Devices”. For USB to work, you need a “USB Host” and a “USB Device” – thus the PC interface. The “tiny utility” your PC is running is a program which tells it how to interact with each of those devices.

So, to replace the PC, you would need a host which can talk to two USB devices and have a program running which knows what each device does and how to interact with each of them. As far as I am aware, there would be no standard program which would automatically do this with any two devices, so I don’t believe there would be any off-the-shelf hardware that would be able to do this as a “plug-and-play” device.

If you have the documentation for devices A and B which covered how they operate (such as whether the sensor device just regularly sends out data or whether it waits for a request to send data), you could probably write a fairly simple application to run on something like a Raspberry Pi, which has several USB host ports. However, they are currently very hard to come by due to component shortages in the market.

If you want to free up your PC for other tasks, your best bet may be to find an old used PC and just dedicate it to this purpose.

Off the shelf hardware like this:

actually use USB over IP: USB/IP - ArchWiki

any off the shelf Linux SBC could do the same thing, Digi’s AW02-G300 does it all in a reconfigured box with lot of other addon’s.


If these are simple USB to RS-232 serial adaptors on the two devices then simply connecting the two RS-232 ports together via a null modem adapter or cable is probably all you need to do.

FYI - a null modem reverses one side of the RS-232 connections so that two DCE (data circuit-terminating equipment) wired devices can communicate without a dual port DTE (data terminal equipment) device in between them. In modern RS-232 systems with no control lines, the only wires used are Rx & Tx so it’s easy to roll your own adaptor out of spare cables or connectors.

Final FYI, for clarity to non-engineers I used the layman’s name of RS-232 in place of the proper name TIA-232.