Allow gyro-less booting

src/main/fc/cli.c

@@ -2711,7 +2711,7 @@ static void cliStatus(char *cmdline)
     const int systemRate = getTaskDeltaTime(TASK_SYSTEM) == 0 ? 0 : (int)(1000000.0f / ((float)getTaskDeltaTime(TASK_SYSTEM)));
     cliPrintLinef("CPU:%d%%, cycle time: %d, GYRO rate: %d, RX rate: %d, System rate: %d",
             constrain(averageSystemLoadPercent, 0, 100), getTaskDeltaTime(TASK_GYROPID), gyroRate, rxRate, systemRate);
-
+    cliPrintLinef("Arming disable flags: 0x%x", getArmingDisableFlags() & ~ARMING_DISABLED_CLI);
 }
 
 #ifndef SKIP_TASK_STATISTICS

src/main/fc/fc_init.c

@@ -478,8 +478,8 @@ void init(void)
     initBoardAlignment(boardAlignment());
 
     if (!sensorsAutodetect()) {
-        // if gyro was not detected due to whatever reason, we give up now.
-        failureMode(FAILURE_MISSING_ACC);
+        // if gyro was not detected due to whatever reason, don't arm.
+        setArmingDisabled(ARMING_DISABLED_NO_GYRO);
     }
 
     systemState |= SYSTEM_STATE_SENSORS_READY;

src/main/fc/fc_tasks.c

@@ -259,8 +259,11 @@ void osdSlaveTasksInit(void)
 void fcTasksInit(void)
 {
     schedulerInit();
-    rescheduleTask(TASK_GYROPID, gyro.targetLooptime);
-    setTaskEnabled(TASK_GYROPID, true);
+
+    if (sensors(SENSOR_GYRO)) {
+        rescheduleTask(TASK_GYROPID, gyro.targetLooptime);
+        setTaskEnabled(TASK_GYROPID, true);
+    }
 
     if (sensors(SENSOR_ACC)) {
         setTaskEnabled(TASK_ACCEL, true);

src/main/fc/runtime_config.c

@@ -46,6 +46,11 @@ bool isArmingDisabled()
     return armingDisableFlags;
 }
 
+armingDisableFlags_e getArmingDisableFlags(void)
+{
+    return armingDisableFlags;
+}
+
 /**
  * Enables the given flight mode.  A beep is sounded if the flight mode
  * has changed.  Returns the new 'flightModeFlags' value.

src/main/fc/runtime_config.h

@@ -40,11 +40,13 @@ typedef enum {
     ARMING_DISABLED_CMS_MENU    = (1 << 7),
     ARMING_DISABLED_OSD_MENU    = (1 << 8),
     ARMING_DISABLED_BST         = (1 << 9),
+    ARMING_DISABLED_NO_GYRO     = (1 << 10),
 } armingDisableFlags_e;
 
 void setArmingDisabled(armingDisableFlags_e flag);
 void unsetArmingDisabled(armingDisableFlags_e flag);
 bool isArmingDisabled(void);
+armingDisableFlags_e getArmingDisableFlags(void);
 
 typedef enum {
     ANGLE_MODE      = (1 << 0),