Copter: add pre-arm check of radio and accel

Only checks throttle channel and accelerometer scaling

ArduCopter/ArduCopter.pde

@@ -359,12 +359,13 @@ static AP_RangeFinder_MaxsonarXL *sonar;
 //Documentation of GLobals:
 static union {
     struct {
-        uint8_t home_is_set        : 1; // 1
-        uint8_t simple_mode        : 1; // 2    // This is the state of simple mode
-        uint8_t manual_attitude    : 1; // 3
-        uint8_t manual_throttle    : 1; // 4
+        uint8_t home_is_set        : 1; // 0
+        uint8_t simple_mode        : 1; // 1    // This is the state of simple mode
+        uint8_t manual_attitude    : 1; // 2
+        uint8_t manual_throttle    : 1; // 3
 
-        uint8_t low_battery        : 1; // 5    // Used to track if the battery is low - LED output flashes when the batt is low
+        uint8_t low_battery        : 1; // 4    // Used to track if the battery is low - LED output flashes when the batt is low
+        uint8_t pre_arm_check      : 1; // 5    // true if the radio and accel calibration have been performed
         uint8_t armed              : 1; // 6
         uint8_t auto_armed         : 1; // 7    // stops auto missions from beginning until throttle is raised
 
@@ -1295,6 +1296,9 @@ static void super_slow_loop()
     if ((g.log_bitmask & MASK_LOG_CURRENT) && motors.armed())
         Log_Write_Current();
 
+    // perform pre-arm checks
+    pre_arm_checks();
+
     // this function disarms the copter if it has been sitting on the ground for any moment of time greater than 25 seconds
     // but only of the control mode is manual
     if((control_mode <= ACRO) && (g.rc_3.control_in == 0) && motors.armed()) {

ArduCopter/motors.pde

@@ -17,6 +17,12 @@ static void arm_motors()
         return;
     }
 
+    // ensure pre-arm checks have been successful
+    if(!ap.pre_arm_check) {
+        return;
+    }
+
+    // ensure we are in Stabilize, Acro or TOY mode
     if ((control_mode > ACRO) && ((control_mode != TOY_A) && (control_mode != TOY_M))) {
         arming_counter = 0;
         return;
@@ -166,6 +172,27 @@ static void init_arm_motors()
     failsafe_enable();
 }
 
+// perform pre-arm checks and set 
+static void pre_arm_checks()
+{
+    // exit immediately if we've already successfully performed the pre-arm check
+    if( ap.pre_arm_check ) {
+        return;
+    }
+
+    // check if radio has been calibrated
+    if(!g.rc_3.radio_min.load()) {
+        return;
+    }
+
+    // check accelerometers have been calibrated
+    if(!ins.calibrated()) {
+        return;
+    }
+
+    // if we've gotten this far then pre arm checks have completed
+    ap.pre_arm_check = true;
+}
 
 static void init_disarm_motors()
 {