Add prevention for turning radio on at any time with arm switch on

src/main/fc/fc_core.c

@@ -158,6 +158,24 @@ void updateArmingStatus(void)
             unsetArmingDisabled(ARMING_DISABLED_BOOT_GRACE_TIME);
         }
 
+        // If switch is used for arming then check it is not defaulting to on when the RX link recovers from a fault
+        if (!isUsingSticksForArming()) {
+            static bool hadRx = false;
+            const bool haveRx = rxIsReceivingSignal();
+
+            const bool justGotRxBack = !hadRx && haveRx;
+
+            if (justGotRxBack && IS_RC_MODE_ACTIVE(BOXARM)) {
+                // If the RX has just started to receive a signal again and the arm switch is on, apply arming restriction
+                setArmingDisabled(ARMING_DISABLED_BAD_RX_RECOVERY);
+            } else if (haveRx && !IS_RC_MODE_ACTIVE(BOXARM)) {
+                // If RX signal is OK and the arm switch is off, remove arming restriction
+                unsetArmingDisabled(ARMING_DISABLED_BAD_RX_RECOVERY);
+            }
+
+            hadRx = haveRx;
+        }
+
         if (IS_RC_MODE_ACTIVE(BOXFAILSAFE)) {
             setArmingDisabled(ARMING_DISABLED_BOXFAILSAFE);
         } else {

src/main/fc/runtime_config.c

@@ -31,9 +31,9 @@ static uint32_t enabledSensors = 0;
 
 #if defined(OSD) || !defined(MINIMAL_CLI)
 const char *armingDisableFlagNames[]= {
-    "NOGYRO", "FAILSAFE", "RX LOSS", "BOXFAILSAFE", "THROTTLE",
+    "NOGYRO", "FAILSAFE", "RX LOSS", "BAD RX", "BOXFAILSAFE",
-    "ANGLE", "BOOT GRACE", "NO PREARM", "ARM SWITCH", "LOAD",
+    "THROTTLE", "ANGLE", "BOOT GRACE", "NO PREARM", "ARM SWITCH",
-    "CALIB", "CLI", "CMS", "OSD", "BST"
+    "LOAD", "CALIB", "CLI", "CMS", "OSD", "BST"
 };
 #endif
 

src/main/fc/runtime_config.h

@@ -38,21 +38,22 @@ typedef enum {
     ARMING_DISABLED_NO_GYRO         = (1 << 0),
     ARMING_DISABLED_FAILSAFE        = (1 << 1),
     ARMING_DISABLED_RX_FAILSAFE     = (1 << 2),
-    ARMING_DISABLED_BOXFAILSAFE     = (1 << 3),
+    ARMING_DISABLED_BAD_RX_RECOVERY = (1 << 3),
-    ARMING_DISABLED_THROTTLE        = (1 << 4),
+    ARMING_DISABLED_BOXFAILSAFE     = (1 << 4),
-    ARMING_DISABLED_ANGLE           = (1 << 5),
+    ARMING_DISABLED_THROTTLE        = (1 << 5),
-    ARMING_DISABLED_BOOT_GRACE_TIME = (1 << 6),
+    ARMING_DISABLED_ANGLE           = (1 << 6),
-    ARMING_DISABLED_NOPREARM        = (1 << 7),
+    ARMING_DISABLED_BOOT_GRACE_TIME = (1 << 7),
-    ARMING_DISABLED_ARM_SWITCH      = (1 << 8),
+    ARMING_DISABLED_NOPREARM        = (1 << 8),
-    ARMING_DISABLED_LOAD            = (1 << 9),
+    ARMING_DISABLED_ARM_SWITCH      = (1 << 9),
-    ARMING_DISABLED_CALIBRATING     = (1 << 10),
+    ARMING_DISABLED_LOAD            = (1 << 10),
-    ARMING_DISABLED_CLI             = (1 << 11),
+    ARMING_DISABLED_CALIBRATING     = (1 << 11),
-    ARMING_DISABLED_CMS_MENU        = (1 << 12),
+    ARMING_DISABLED_CLI             = (1 << 12),
-    ARMING_DISABLED_OSD_MENU        = (1 << 13),
+    ARMING_DISABLED_CMS_MENU        = (1 << 13),
-    ARMING_DISABLED_BST             = (1 << 14)
+    ARMING_DISABLED_OSD_MENU        = (1 << 14),
+    ARMING_DISABLED_BST             = (1 << 15)
 } armingDisableFlags_e;
 
-#define NUM_ARMING_DISABLE_FLAGS 15
+#define NUM_ARMING_DISABLE_FLAGS 16
 
 #if defined(OSD) || !defined(MINIMAL_CLI)
 extern const char *armingDisableFlagNames[NUM_ARMING_DISABLE_FLAGS];

src/test/unit/arming_prevention_unittest.cc

@@ -67,6 +67,7 @@ extern "C" {
 
 uint32_t simulationTime = 0;
 bool gyroCalibDone = false;
+bool simulationHaveRx = false;
 
 #include "gtest/gtest.h"
 
@@ -159,7 +160,6 @@ TEST(ArmingPreventionTest, CalibrationPowerOnGraceAngleThrottleArmSwitch)
     EXPECT_EQ(0, getArmingDisableFlags());
     EXPECT_FALSE(isArmingDisabled());
 }
-
 TEST(ArmingPreventionTest, ArmingGuardRadioLeftOnAndArmed)
 {
     // given
@@ -281,11 +281,76 @@ TEST(ArmingPreventionTest, Prearm)
     EXPECT_FALSE(isArmingDisabled());
 }
 
+TEST(ArmingPreventionTest, RadioTurnedOnAtAnyTimeArmed)
+{
+    // given
+    simulationTime = 30e6; // 30 seconds after boot
+    gyroCalibDone = true;
+
+    // and
+    modeActivationConditionsMutable(0)->auxChannelIndex = 0;
+    modeActivationConditionsMutable(0)->modeId = BOXARM;
+    modeActivationConditionsMutable(0)->range.startStep = CHANNEL_VALUE_TO_STEP(1750);
+    modeActivationConditionsMutable(0)->range.endStep = CHANNEL_VALUE_TO_STEP(CHANNEL_RANGE_MAX);
+    useRcControlsConfig(NULL);
+
+    // and
+    rxConfigMutable()->mincheck = 1050;
+
+    // and
+    rcData[THROTTLE] = 1000;
+    ENABLE_STATE(SMALL_ANGLE);
+
+    // and
+    // RX has no link to radio
+    simulationHaveRx = false;
+
+    // and
+    // arm channel has a safe default value
+    rcData[4] = 1100;
+
+    // when
+    updateActivatedModes();
+    updateArmingStatus();
+
+    // expect
+    EXPECT_FALSE(isUsingSticksForArming());
+    EXPECT_FALSE(isArmingDisabled());
+    EXPECT_EQ(0, getArmingDisableFlags());
+
+    // given
+    // RF link is established and arm switch is turned on on radio
+    simulationHaveRx = true;
+    rcData[4] = 1800;
+
+    // when
+    updateActivatedModes();
+    updateArmingStatus();
+
+    // expect
+    EXPECT_FALSE(isUsingSticksForArming());
+    EXPECT_TRUE(isArmingDisabled());
+    EXPECT_EQ(ARMING_DISABLED_BAD_RX_RECOVERY | ARMING_DISABLED_ARM_SWITCH, getArmingDisableFlags());
+
+    // given
+    // arm switch turned off by user
+    rcData[4] = 1100;
+
+    // when
+    updateActivatedModes();
+    updateArmingStatus();
+
+    // expect
+    EXPECT_FALSE(isUsingSticksForArming());
+    EXPECT_FALSE(isArmingDisabled());
+    EXPECT_EQ(0, getArmingDisableFlags());
+}
+
 // STUBS
 extern "C" {
     uint32_t micros(void) { return simulationTime; }
     uint32_t millis(void) { return micros() / 1000; }
-    bool rxIsReceivingSignal(void) { return false; }
+    bool rxIsReceivingSignal(void) { return simulationHaveRx; }
 
     bool feature(uint32_t) { return false; }
     void warningLedFlash(void) {}