RV50 Serial Port DCD line

We use the serial port DCD signal on the RV50 to give us status for when a TCP connection is active with a remote device. In AceManager we have Assert DCD set to in Data Mode (AT&C1). We have the modem configured for TCP auto answer on port 12345. When a remote TCP client connects to the modem, it auto answers and the DCD line goes from low to high as expected. When we close the TCP connection, DCD goes back low as expected. If we issue an ATDT[IP]/PORT command to initiate a client TCP connection from the modem to a remote server that is currently NOT listening, the DCD line is immediately going high anyway. DCD should only go high after a successful TCP connection is established shouldn’t it? At least this is how it worked in the past with Redwing, Raven, LS300, and RV50s etc… DCD seems to go high for the entire time period that the ATDT command is waiting for a TCP connection to be established, when a timeout occurs and a “NO ANSWER” result is sent over the serial port, DCD finally goes back low. Is there some setting other than AT&C1 that is required to allow DCD to function properly?

Hi @gregsuzy

Which ALEOS firmware version are you using?

I first saw the behavior with ALEOS v4.9.0.040. I then upgraded to v4.13.0.017 and I still see the same issue.

Hi @gregsuzy

It is known issue. Sierra Wireless is aware of this issue.
I have some information from the software team that I want to give you.
“It has been decided there will be no change to remove the momentary assertion of the DCD line on ATDT dialing. This has been the behavior for some time and making a change may break some customer installations.
The behavior of this line will be reviewed in future software platforms, but will not be changed in ALEOS.”

Please help to tick “Solution” if your questions is answered.

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