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by anonymous
I need to connect the TRB255 to an ARM computer with a 2-wires RS485 connection. I short-circuited R+/D+ and R-/D- as per your manual.

Now I'm trying to send AT commands from the ARM computer but I get no answer from the modem. I'm simply doing an

echo AT > /dev/ttyS1

and, on another terminal,

cat /dev/ttyS1

Current configuration is 9600, databits 8, parity None stopbits 1, flow control None, serial type Console, Full Duplex OFF

1 Answer

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by anonymous
Hello,

First of all, I would suggest double-checking your wire (is it working with other devices, and if you 100% correctly connected wires as this guide shows: https://wiki.teltonika-networks.com/view/TRB255_RS485#2-Wire_and_4-Wire_Networks)

Secondly, you could play around with configuration settings, changing baud rate, data bits. Also, I would like to know what is connected to the other end of the RS485 cable.

Regards.
by anonymous
Yes, I followed exactly that guide to connect the wires. On the other side there is an electronic board running Linux, on an ARM processor with a RS485 port. Should I power off/on the modem when I change the settings? Also, is the procedure I'm following correct from a global point of view?
by anonymous
Ok, I success in communicating in RS485. Now I expected to send AT commands with the modem responding, but instead I receive "password". I think the modem is asking me to authenticate in a kind of console, but I just want to send commands and get responses to them
by anonymous
Hello,

First of all, you must authenticate by using the default username root and your WebUI password.
by anonymous
sorry, I think the point is not clear. I need to send SMS programmatically (in C language) using this modem connected to an RS485 port.

With the modems I used so far, I simply opened the serial port and send AT commands with a write to the port.
by anonymous
Unfortunately, this is not the case with our routers. You need to authenticate atleast once before sending any commands.