I am trying to communicate with a serial device over IP to RS232/RS485.
I have a virtual COM-Port running on my computer in order to send and receive data from there.
In the direction from the computer to the serial device, everything is working fine. But in the reverse direction, if too much data is fed from the serial port to the Router, the transmission is stopped and further data is lost. Only after a small pause data can be sent to the computer again. Is this a known issue? If yes, is there a solution?
This is not a known issue. Perhaps you could post a screenshot of the Serial over IP serial configuration window?
If your serial device supports it, have you tried using flow control?
Does the issue replicate on both RS232 and RS485 connections? Was the full-duplex RS485 connection tried?
One more idea I have, is the MTU of the mobile connection might be too big. Please try changing it by navigating to Network → Interfaces → General, edit the mob1s1a1 interface (if SIM1 is used), and in the advanced settings change the Override MTU option to 1250 and check again. If an improvement is seem, the MTU can be raised back up to around 1420.
I tried flow control and RS232 and RS485 (half duplex). Both with no success. The Transmission stops at around 128Bytes of continuous data.
I am not using the SIM Card as I am testing with WLAN/LAN right now, so changing the MTU of the SIM shouldn’t change anything, does it?
I also recognized that the firmware is open source. Is it possible to change the buffer size of the Serial Driver or increase its scheduling priority? If yes, where can I do so?
I also attached pictures of the Serial over IP config page.
The highest supported baud rate for RUT956 is 115200. Could you try lowering the baud rate of the serial device and checking if the OverIP feature works then?
Additionally, for higher baud rates we recommend avoiding the use of longer cables. If half-duplex connection is used, make sure to bridge the pins 1 and 2, as well as 4 and 5 on the 6-pin RS485 connector. More information can be found here: RUT956 Serial Utilities - Teltonika Networks Wiki
