Sub: Remove unused ap.usb_connected flag

ArduSub/ArduSub.cpp

@@ -382,8 +382,6 @@ void Sub::one_hz_loop()
     // update assigned functions and enable auxiliary servos
     SRV_Channels::enable_aux_servos();
 
-    check_usb_mux();
-
     // update position controller alt limits
     update_poscon_alt_max();
 

ArduSub/GCS_Mavlink.cpp

@@ -1885,7 +1885,6 @@ void Sub::mavlink_delay_cb()
         last_5s = tnow;
         gcs_send_text(MAV_SEVERITY_INFO, "Initialising APM");
     }
-    check_usb_mux();
 
     in_mavlink_delay = false;
 }

ArduSub/Sub.h

@@ -228,7 +228,6 @@ private:
         struct {
             uint8_t pre_arm_check       : 1; // true if all pre-arm checks (rc, accel calibration, gps lock) have been performed
             uint8_t logging_started     : 1; // true if dataflash logging has started
-            uint8_t usb_connected       : 1; // true if APM is powered from USB connection
             uint8_t compass_mot         : 1; // true if we are currently performing compassmot calibration
             uint8_t motor_test          : 1; // true if we are currently performing the motors test
             uint8_t initialised         : 1; // true once the init_ardupilot function has completed.  Extended status to GCS is not sent until this completes
@@ -669,7 +668,6 @@ private:
     bool position_ok();
     bool ekf_position_ok();
     bool optflow_position_ok();
-    void check_usb_mux(void);
     bool should_log(uint32_t mask);
     void gcs_send_text_fmt(MAV_SEVERITY severity, const char *fmt, ...);
     bool start_command(const AP_Mission::Mission_Command& cmd);

ArduSub/system.cpp

@@ -55,11 +55,6 @@ void Sub::init_ardupilot()
     // hal.scheduler->delay.
     hal.scheduler->register_delay_callback(mavlink_delay_cb_static, 5);
 
-    // we start by assuming USB connected, as we initialed the serial
-    // port with SERIAL0_BAUD. check_usb_mux() fixes this if need be.
-    ap.usb_connected = true;
-    check_usb_mux();
-
     // setup telem slots with serial ports
     for (uint8_t i = 0; i < MAVLINK_COMM_NUM_BUFFERS; i++) {
         gcs_chan[i].setup_uart(serial_manager, AP_SerialManager::SerialProtocol_MAVLink, i);
@@ -284,17 +279,6 @@ bool Sub::optflow_position_ok()
 #endif
 }
 
-void Sub::check_usb_mux(void)
-{
-    bool usb_check = hal.gpio->usb_connected();
-    if (usb_check == ap.usb_connected) {
-        return;
-    }
-
-    // the user has switched to/from the telemetry port
-    ap.usb_connected = usb_check;
-}
-
 /*
   should we log a message type now?
  */