APM的解锁（ARM）流程

• 解锁检测函数

              解锁检测函数是arm_motors_check（），作为scheduler每秒运行10此，定义在motors.cpp中，定义如下

#define ARM_DELAY               20  // called at 10hz so 2 seconds
#define DISARM_DELAY            20  // called at 10hz so 2 seconds
#define AUTO_TRIM_DELAY         100 // called at 10hz so 10 seconds
#define LOST_VEHICLE_DELAY      10  // called at 10hz so 1 second

static uint8_t auto_disarming_counter;

// arm_motors_check - checks for pilot input to arm or disarm the copter
// called at 10hz
void Copter::arm_motors_check()
{
    static int16_t arming_counter;

    // ensure throttle is down
    if (channel_throttle->control_in > 0) {
        arming_counter = 0;
        return;
    }

    int16_t tmp = channel_yaw->control_in;

    // full right
    if (tmp > 4000) {

        // increase the arming counter to a maximum of 1 beyond the auto trim counter
        if( a