EC21 PPP Mode No Echo

IoT Modules LTE Standard Module
1

Hi all

I’m trying to setup a PPP Connection over a standard RS232 Port with a Teltonika TRB142 (Quectel EC21 Modem) and Campbell Scientific CR350 Data Logger.

This is the modem firmware:

EC21AUFAR06A06M4G_01.001.01.001

I can successfully setup the modem (TRB142) as a dialup connection in windows and connect successfully over the rs232 port.
However I have been unsuccessful with the CR350 and TRB142.
The CR350 is sending “AAAA+++ATH” continuously out on the serial port and never seems to get a reply form the modem.
I have tried turning echo on “ATE1”, but still nothing changes on the CR350.
Is there some other type of echo that I need to enable on the modem.
I have read everything that I can find on the internet.

My problem seems similar to this forum.

I have tried crossover and straight thru cables, without success.
Any help much appreciated. Cheers

2

A guard time (no character activity) is required on both sides of the +++

So <guard time>+++<guard time>ATH

With the guard time in place, +++ switches the modem from data mode to command mode.

From memory, 2 or 3 seconds should be adequate.

3

Hi

I understand this. But the modern is already in command mode. Waiting for the CR350 to dail and initiate the connection.
I don’t understand what the CR350 is expecting/waiting for.. When I google it, all I can find is that the CR350 expects to get the A echoed back. Then it will start setting the ppp connection up. But how do I enable this.