Differences

This shows you the differences between two versions of the page.

--- telephony:td816-serial [2025/03/23 20:52] – created prppedro
+++ telephony:td816-serial [2025/03/23 21:23] (current) – [Into the rabbit hole] prppedro
@@ Line 37: / Line 37: @@
 Nevertheless, some sections do work and I suspect you can easily do some basic changes, like time and date. And this was sufficient pretext to throw me into a whole new rabbit hole: to understand how the software communicates with the PBX and maybe learn something in the process.
 ## Into the rabbit hole
+Okay, so this software is obviously suboptimal: I don't want to run it just to get system status or adjust the clock to NTP. Also, I very much don't want to rely on old OS platforms to do this. So, know what time is it? ~~It is time to stop~~ Time to spend an entire weekend trying to sniff serial traffic, fail miserably, learn stuff along the way and write this article out of frustration and need to write down some of those learnings, so they don't get completely vanished, after my brain clears it's cache.
+So, to be clear, **I didn't** succeed, thus far. Anyway, let's roll...
+### Setting the theatre
+This thing is running inside DOSBox, and DOSBox is directly tied to the serial port (`serial1=directserial realport:ttyS0`). The host system is a fairly modern i5-6300 laptop, using a proprietary Dell dock which provides access to the serial port, although I don't think this detail particularly matters... The cable is an entire chapter on it's own, because it was constructed out of a Cisco-compatible RJ-45->DB-9 cable, a Cat.5E keystone and an old printer cable going into that keystone. However, the wiring is basically a run-of-the-mill DB-25->DB-9 null modem cable.
+Connecting PuTTY to `/dev/ttyS0` gets me that message we mentioned before (`ATQ0E0V1S0=1X0&D0`), and now it's time to explain what it is: whenever the PABX detects a terminal device connected to it's serial port,
+it sends those commands. If the device is a modem, this command will initialize the modem. It's an [Hayes AT command](https://en.wikipedia.org/wiki/Hayes_AT_command_set), that can also be written as individual commands, like this:
+```
+ATQ0
+ATE0
+ATV1
+ATS0=1X0
+D0 (?)
+```
+ATQ0 sends the modem into quiet mode, ATE0 disables echoing, ATV1 calls for verbal result codes and ATS0=1X0 sets the modem to auto-answer after one ring. I really don't know much about the D0.
+This may not matter much to us, now, but might matter a bit further down the road.
+After this string, the PBX will print SMDR records.
+And that's everything you'll get from it by using PuTTY. The unit won't respond to anything you type.

Tadeu's Wiki

User Tools

Site Tools

Differences

Page Tools