Hi Everyone, I'm having trouble using a USB modem. It is a Conexant modem but it is not responding to AT commands. Sample code is at https://pastebin.com/84YUn9ey . I think the first thing I need to do is verify the kernel configuration for the device. For that: $ sudo setserial -a /dev/ttyACM0 /dev/ttyACM0, Line 0, UART: unknown, Port: 0x0000, IRQ: 0 Baud_base: 115200, close_delay: 12, divisor: 0 closing_wait: 750 Flags: spd_normal At this point I think I need to read some kernel docs. I'm not sure if I should be in https://www.kernel.org/doc/Documentation/serial or https://www.kernel.org/doc/Documentation/usb . Looking through the pages nothing jumps out as specific to the Conexant. Can someone suggest what my next steps are to verify the modem's configuration with respect to the kernel and driver? Thanks in advance.