Device with inborn RS232 Serial Port to use with ser2net

Hello everyone,

I would like to have a little box achieving one mission only : standing in the network as a serial port bridge to whatever device. I would like it to have a RS232 Serial Port out of the box (not needing to attach to it an "USB to TTL convertor" or anything alike) and that (needless to say) would be able to host OpenWrt, in order to run ser2net.

Any ideas ? And again : please, no suggestions about an usb cable extension.

Two serial ports (one for the kernel/OS, one for your application), Ethernet, 802.11n (2.4 GHz), OEM firmware is directly based on OpenWrt (18.06 at this time), ~US$20

Hello Jeff,

thanks for your reply, but it doesn't fit my demand : what I mean is a true DB9 port like this one.

Those are very rare on consumer/ prosumer routers, you'll basically only find them (respectively variants (proprietary socket, but rs232c signalling and signal levels) thereof) on professional/ enterprise'y devices (and usually exclusively for recovery/ administration access, not usable for rs232c devices); obviously aside from (some-) x86/ x86_64 mainboards.

Indeed, what I'm looking for has a dedicated name : "serial device server".
And googling this name listed numerous gears, most of them quite expensive ( >100$ ).
Anyway, if someone knows, in the Table Of Hardware, of a device that would fill the bill....

I doubt any all-in-one provides RS232 signaling (+/-15 V) signaling. Similarly, anything but TX/RX is very unlikely. A USB dongle is required for even current desktops and laptops.

In fact, the +/-15V is not RS232, it was at the very beginning, but with RS232c it went to +/-5V only.
RS232c is in fact, what everybody means when talking about RS232.
(thanks go to slh, who by using the rs232c term made me googled about it. Before that, I did not knew there was even such a thing as +/-15V at the very beginning of the RS232 history).

Jeff, I get your point, that there is no way other than an USB dongle, but having clafified that it's only a +/-5v range, won't there be any candidate device ?

I do have several devices that require differential signaling, and several that require the additional lines. Even if 5 V thresholds are sufficient, a long run requires higher drive levels.

SoCs in all-in-one devices are 3.3 V or lower. You’ll need a bidirectional, charge-pump, differential level-shifter at a minimum. They’ve been around for decades. I purchased Ultra Compact RS232 to TTL Converter with Male DB9 (1.8V 3.3V 5V, up to 1Mbps) a while ago for a specific application that needed access to one of the control lines and fit in a DB9 hood. Pick your DB9 gender and DTE vs. DCE carefully. Make sure the control lines you need are supported. Breakout boards are also available from various sources.


Thanks Jeff for the insights and the item reference.

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