Strange AT command behavior
Posted: Tue Jan 31, 2023 6:26 pm
Looke what I found
Recently found my old 3g modem. Had a feeling it was a mPCIe card inside. Indeed it is.
I am seeing some strange behavior when trying to access AT commands on this Novatel USB720 modem.
My machine is running MX linux, and I also installed minicom.
When I plug in the USB modem and try to access the serial port with it sometimes takes a few tries before it will connect. When it does not connect, I get a return error message "Permission Denied".
When it does finally connect, the terminal automatically types , then sends to device. Returns "Error" multiple times (not consistent), and eventually returns an "OK".
During this time no user input is being provided.
If I try to type in a command while this is happening, whatever I type is overwritten or sent automatically.
There appears to be around a 2 second delay between each response in the terminal.
After aroumd 10-20 responses (usually "Error") in the terminal, the serial com locks up and will not respond to further input. Ending the serial com and reopening does not help. Only removing and plugging in the USB again will free it up.
Note this behavior is similar before and after minicom was installed.
I have a feeling this is due to incorrect baud rate being set by default when the modem is plugged in, but attempting to change the baud rate with minicom does not appear to have any affect?
Is this normal behavior? I have not found any help for this after searching around the net for a few days.
Recently found my old 3g modem. Had a feeling it was a mPCIe card inside. Indeed it is.
I am seeing some strange behavior when trying to access AT commands on this Novatel USB720 modem.
My machine is running MX linux, and I also installed minicom.
When I plug in the USB modem and try to access the serial port with
Code: Select all
socat - /dev/ttyUSB0When it does finally connect, the terminal automatically types
Code: Select all
AT$NWMAT=1During this time no user input is being provided.
If I try to type in a command while this is happening, whatever I type is overwritten or sent automatically.
There appears to be around a 2 second delay between each response in the terminal.
After aroumd 10-20 responses (usually "Error") in the terminal, the serial com locks up and will not respond to further input. Ending the serial com and reopening does not help. Only removing and plugging in the USB again will free it up.
Note this behavior is similar before and after minicom was installed.
I have a feeling this is due to incorrect baud rate being set by default when the modem is plugged in, but attempting to change the baud rate with minicom does not appear to have any affect?
Is this normal behavior? I have not found any help for this after searching around the net for a few days.