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I'm trying to establish a transparent RS485 link with two TRB145 gateways. To start with both units have a sim card with public IP addresses.  RS485 parameters are 1200 baud, 8N1 and the ip port used is 5000. Reconnect interval 60 seconds. Both units had in first instance the TRB1450_R_00.02.03.2_LEGACY.bin firmware.

The "RS485" server TRB145 just works fine. I can connect to it with the Hercules (TCP Client) software and it stays reliable connected. With the v2.03.2 firmware.

But the "RS485" client is another story. It just don't work or is notoriously unstable. I just couldn't get it to work with the v2.03.2 firmware. It looks like the unit hangs (CPU load is nearly 100%) and the  Tx led next to the sim card never goes off. The simcard is registered to the network and obtained an ip (public) address. The I decided to downgrade the firmware to TRB1450_R_00.01.06.1. After setting the unit up with the above settings the unit connected to the server and everything looked fine. But after a power down the same issue appeared, no link and the Tx led next to the simcard continuously on. A hard reset reverting to the default state and setting up again didn't resolve the issue. Flashing the v1.06.1 firmware with the checkbox "keep settings" unchecked and after that setting up the device again did the job. But only until a power down. After the power down the same issue came up again. After several hours trying I'm now out of options. What else can I do/try?

Thank you in advance!

Addition to my question:

When I set the RS485 configuration to "off" and back to "on" the Tx led next to the simcard goes off and the unit connects to the server and RS485 traffic over internet works. But after a power cycle the same issue is back. However changing RS485 configuration to "off" and back to "on" does the trick again. Until the next power cycle...........


We are also experiencing stability issues with the RS485 Client  in TRB14X_R_00.02.04.1 (in that it keeps dropping its connection to our server). This will likely explain your issue too. 

In RS485 Client mode the modem continually drops its connection and reconnects every "timeout interval". It should stay connected as it used to (eg. in previous firmwares for TRB145 and other devices like the TRB255 are successful at this).

Would be good to know how soon this will get resolved.

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Hey Arend,

Could you please send your network topology for better understanding? i mean, like this: PLC <-rs485-> trb145 <-gsm-> trb145 <-rs485-> SCADA...

If PLC and SCADA "talk" the same protocol, did you try to configure your routers with transparent feature without the modbus conversion?
Hi Wesley,

Thank you for your reply. My network topology is as follows:

Datalogger with RS485 port (2 wire) -> TRB145(simcard with public ip address) --> GSM network --> TRB145 (simcard with public ip address) --> PLC with RS485 port (2 wire)

The serial baudrate is low: 1200 baud (bps) 8N1.

I didn't use the "modbus" feature but the "over ip" settings.

A message of 20 characters is sent to the PLC every 1 minute.

The TRB145 RS485 link does work but after a power cycle it doesn't anymore. To get it up and running I have to switch the RS485 off and on in the "Services->RS485" settings of the RS485 client.




My uci show rs file:


In addition to my comment above, I would assume that you're using IPSec to secure the communications between the routers. If that is the case, it may be that if you power cycle 1 device its peer has not discovered that the secure tunnel has been dropped and so is not in a position to establish a new one?

Have your SIM cards been provided with Static IPs? Telco's don't like giving these out, so even though rebooting your modems a few times to test may result in getting the same IP address by conincidence (telcos will reserve these for a fixed period to ensure fast continuity of service), be aware that they may change over time.

In July I gave up, the issue took me many 10th of waisted hours. Removed the TRB145 units and replaced them for another brand. But I have still these units and decided to give it a new try. I have made a test with firmware  TRB1450_R_00.01.06.1.bin, TRB1450_R_00.02.03.2_LEGACY.bin and TRB14X_R_00.02.04.3_WEBUI.bin and the only version with which the link work is 01.06.1 version. With the other versions the transparent RS485 link just does not work. In my opinion it is caused by the server, if I use a server on my pc every fw version works as client. When I use the 01.06.1 version there is a quirck, I have to switch off and then on again the RS485 link in the menu. Then the link will be established and is stable.

What I would ask from the guys at Teltonika to try it by themselves, with SIM cards with a public ip addres (not fixed) and the dynamic dns service from dyn.com. Or is there someone who succeeded in creating a link with the newer firmware versions?