Wait for +++ to switch USB output from GNSS to status and debug msgs

Author: LeeLeahy2

Firmware/RTK_Everywhere/RTK_Everywhere.ino

@@ -461,6 +461,13 @@ float batteryChargingPercentPerHour;
 // USB serial port and PC.
 volatile bool forwardGnssDataToUsbSerial;
 
+// Timeout between + characters to enter the +++ sequence while
+// forwardGnssDataToUsbSerial is true.  When sequence is properly entered
+// forwardGnssDataToUsbSerial is set to false and menuMain is displayed.
+// If the timeout between characters occurs or an invalid character is
+// entered then no changes are made and the +++ sequence must be re-entered.
+#define PLUS_PLUS_PLUS_TIMEOUT      (2 * 1000)  // Milliseconds
+
 #define platformPrefix platformPrefixTable[productVariant] // Sets the prefix for broadcast names
 
 #include <driver/uart.h>    //Required for uart_set_rx_full_threshold() on cores <v2.0.5

Firmware/RTK_Everywhere/menuMain.ino

@@ -11,6 +11,7 @@ void terminalUpdate()
         periodicDisplay = settings.periodicDisplay;
     }
 
+    // Check for USB serial input
     if (systemAvailable())
     {
         byte incoming = systemRead();
@@ -21,7 +22,40 @@ void terminalUpdate()
             printCurrentConditionsNMEA();
         }
         else
+        {
+            // When outputting GNSS data to USB serial, check for +++
+            if (forwardGnssDataToUsbSerial)
+            {
+                static uint32_t plusTimeout;
+                static uint8_t plusCount;
+
+                // Reset plusCount on timeout
+                if ((millis() - plusTimeout) > PLUS_PLUS_PLUS_TIMEOUT)
+                    plusCount = 0;
+
+                // Check for + input
+                if (incoming != '+')
+                {
+                    // Must start over looking for +++
+                    plusCount = 0;
+                    return;
+                }
+                else
+                {
+                    // + entered, check for the +++ sequence
+                    plusCount++;
+                    if (plusCount < 3)
+                    {
+                        // Restart the timeout
+                        plusTimeout = millis();
+                        return;
+                    }
+
+                    // +++ was entered, display the main menu
+                }
+            }
             menuMain(); // Present user menu
+        }
     }
 }