Update menu_system.md

Author: nseidle

docs/menu_system.md

@@ -76,12 +76,13 @@ System Menu Options serial menu
 
 The device can be in Rover, Base, or WiFi Config mode. The selected mode will be entered once the user exits the menu system.
 
-- **B, R, W, or S** - Change the mode the device is in.
+- **B, C, R, W, or S** - Change the mode the device is in.
 
-	- Rover - This is the default mode. The device transmits its NMEA and other messages (if enabled) over Bluetooth. It can receive corrections over Bluetooth (or other transport methods such as NTRIP Client) to achieve RTK Fix.
-	- Base - The device will reconfigure for base mode. It will begin transmitting corrections over Bluetooth, WiFi (NTRIP Server, TCP, etc), or other (ESP-Now, external radio if compatible, etc).
-	- WiFi Config - The device will shut down GNSS operations and begin broadcasting as a WiFi Access Point (or will attempt to connect to local WiFi). Once started, the device can be connected to over WiFi for configuration.
-	- Shut Down - If supported, the device will immediately shut down.
+	- **B**ase - The device will reconfigure for base mode. It will begin transmitting corrections over Bluetooth, WiFi (NTRIP Server, TCP, etc), or other (ESP-Now, external radio if compatible, etc).
+	- Base**C**aster - The device will reconfigure for base caster mode. It will broadcast a WiFi access point, allow incoming NTRIP Client connections on port 2101. See [BaseCast Mode](menu_base.md#base-cast).
+	- **R**over - This is the default mode. The device transmits its NMEA and other messages (if enabled) over Bluetooth. It can receive corrections over Bluetooth (or other transport methods such as NTRIP Client) to achieve RTK Fix.
+	- **W**eb Config - The device will shut down GNSS operations and serve a configuration web page over WiFi or ethernet.
+	- **S**hut Down - If supported, the device will immediately shut down.
 
 ## Settings