Update README.md

atc/fib-fm350_gl/README.md

@@ -21,6 +21,8 @@ wget https://github.com/mrhaav/openwrt/raw/master/atc/fib-fm350_gl/atc-fib-fm350
 opkg install atc-fib-fm350_gl_2024-04-26-0.2_all.ipk
 ```
 \
+If you have `AT+GTUSBMODE=40` (0e8d:7126) then the AT-command port is ttyUSB2 and with `AT+GTUSBMODE=41` (0e8d:7127) the AT-command port is ttyUSB4.
+\
 If the script doesn´t work, check in syslog. If it stops at ` offline -> registered - .....` then your service provider doesn´t use NITZ and disconnections can´t be detected. You can use `atc-fib-fm350_gl_2024-04-24-0.2_all.ipk` instead, but you have to check network connectivity by your self.
 
 \