XBEE Cell AT&T PPP modem is hanging up after IPCP

After IPCP sent from modem, I never get a response from the network and then the modem hangs up and is stuck in data mode until I hard reset it.

OS is Ubuntu 20.04, with ModemManager service turned off for now.
The SIM card is the one that comes with the XBee3 from Digi, if that helps.

Any ideas as to why I am getting the hang up? How can I ensure that the modem is in command mode, or ensure the modem is reset properly after I get the hang up?


Rob, where are you located? Does the radio connect and remain connected when NOT using bypass mode?

Located in the US. FYI… This is happening with all 4 of the XBee modems I have. I’ll flip one back to “regular” mode and see what I get. Any params you want me to report on?

AI shows 0x0 on the one I changed back, also have an IP address in MY.

This would indicate that there is an issue in your connection script as the SIM and modem are working fine.

Yes, the chat script is the “stock” one from the PPP How-To. When it does connect, it then sends the IPCP request, and then the modem hangs up immediately after that request is sent. The network never send a reply. This happens on all four modems, same carrier.

which interface board are you working with?

How is that board connected to the PC?

How are you powering this board?

If you are using the XBIB-CU-Th board, what port is the USB C port plugged into on that PC? Is it connected to another USB C port?

Digi XBee 3 Cell LTEM/NBIoT Kit (AT&T), part number (1P)XK3-CA2-T-UB

Board is configured for USB Direct Mode, attached to an Ubuntu 20.04 Desktop via The USB C cable for power and the USB Micro to USB Direct connection.

Thanks again in advance for the help!

Rob, this is a know issue and should be resolved once the next version of firmware is released for both the U-Blox and XBee firmware.

Thank You for all your help on this one!!