I loaded the pl2303 module with debug=1 option, this is the relevant part where I entered ATDT and received ERROR. Mar 4 15:43:03 [kernel] pl2303 ttyUSB0: pl2303_send - length = 3, data = 54 5a 0d Mar 4 15:43:03 [kernel] drivers/usb/serial/pl2303.c: pl2303_write_bulk_callback - port 0 Mar 4 15:43:03 [kernel] drivers/usb/serial/pl2303.c: pl2303_send - port 0 Mar 4 15:43:05 [kernel] drivers/usb/serial/pl2303.c: pl2303_read_bulk_callback - port 0 Mar 4 15:43:05 [kernel] pl2303 ttyUSB0: pl2303_read_bulk_callback - length = 9, data = 54 5a 0d 0d 0a 4f 4b 0d 0a Mar 4 15:43:05 [kernel] drivers/usb/serial/pl2303.c: pl2303_read_bulk_callback - tty_flag = 0 Mar 4 15:43:05 [kernel] drivers/usb/serial/pl2303.c: pl2303_ioctl (0) cmd = 0x5402 Mar 4 15:43:05 [kernel] drivers/usb/serial/pl2303.c: pl2303_ioctl not supported = 0x5402 Mar 4 15:43:05 [kernel] drivers/usb/serial/pl2303.c: pl2303_set_termios - port 0 Mar 4 15:43:05 [kernel] drivers/usb/serial/pl2303.c: 0xa1:0x21:0:0 7 - 0 c2 1 0 0 0 8 Mar 4 15:43:05 [kernel] drivers/usb/serial/pl2303.c: pl2303_set_termios - data bits = 8 Mar 4 15:43:05 [kernel] drivers/usb/serial/pl2303.c: pl2303_set_termios - baud = 9600 Mar 4 15:43:05 [kernel] drivers/usb/serial/pl2303.c: pl2303_set_termios - stop bits = 1 Mar 4 15:43:05 [kernel] drivers/usb/serial/pl2303.c: pl2303_set_termios - parity = none Mar 4 15:43:05 [kernel] drivers/usb/serial/pl2303.c: 0x21:0x20:0:0 7 Mar 4 15:43:05 [kernel] drivers/usb/serial/pl2303.c: 0xa1:0x21:0:0 7 - 80 25 0 0 0 0 8 Mar 4 15:43:05 [kernel] drivers/usb/serial/pl2303.c: 0x40:0x1:0x0:0x0 0 Mar 4 15:43:05 [kernel] drivers/usb/serial/pl2303.c: set_control_lines - value = 3, retval = 0 Can someone guide me on how to debug this? Many thanks.
