arming: added PWM_SERVO_SET_ARM_OK and PWM_SERVO_CLEAR_ARM_OK

these new ioctls allow for the flight code to tell the IO board that
arming can proceed

Author: Andrew Tridgell

src/drivers/drv_pwm_output.h

@@ -109,6 +109,12 @@ ORB_DECLARE(output_pwm);
 /** selects servo update rates, one bit per servo. 0 = default (50Hz), 1 = alternate */
 #define PWM_SERVO_SELECT_UPDATE_RATE _IOC(_PWM_SERVO_BASE, 4)
 
+/** set the 'ARM ok' bit, which activates the safety switch */
+#define PWM_SERVO_SET_ARM_OK	_IOC(_PWM_SERVO_BASE, 5)
+
+/** clear the 'ARM ok' bit, which deactivates the safety switch */
+#define PWM_SERVO_CLEAR_ARM_OK	_IOC(_PWM_SERVO_BASE, 6)
+
 /** set a single servo to a specific value */
 #define PWM_SERVO_SET(_servo)	_IOC(_PWM_SERVO_BASE, 0x20 + _servo)
 

src/drivers/px4fmu/fmu.cpp

@@ -606,6 +606,11 @@ PX4FMU::pwm_ioctl(file *filp, int cmd, unsigned long arg)
 		up_pwm_servo_arm(true);
 		break;
 
+	case PWM_SERVO_SET_ARM_OK:
+	case PWM_SERVO_CLEAR_ARM_OK:
+		// these are no-ops, as no safety switch
+		break;
+
 	case PWM_SERVO_DISARM:
 		up_pwm_servo_arm(false);
 		break;

src/drivers/px4io/px4io.cpp

@@ -1358,6 +1358,16 @@ PX4IO::ioctl(file *filep, int cmd, unsigned long arg)
 		ret = io_reg_modify(PX4IO_PAGE_SETUP, PX4IO_P_SETUP_ARMING, 0, PX4IO_P_SETUP_ARMING_FMU_ARMED);
 		break;
 
+	case PWM_SERVO_SET_ARM_OK:
+		/* set the 'OK to arm' bit */
+		ret = io_reg_modify(PX4IO_PAGE_SETUP, PX4IO_P_SETUP_ARMING, 0, PX4IO_P_SETUP_ARMING_IO_ARM_OK);
+		break;
+
+	case PWM_SERVO_CLEAR_ARM_OK:
+		/* clear the 'OK to arm' bit */
+		ret = io_reg_modify(PX4IO_PAGE_SETUP, PX4IO_P_SETUP_ARMING, PX4IO_P_SETUP_ARMING_IO_ARM_OK, 0);
+		break;
+
 	case PWM_SERVO_DISARM:
 		/* clear the 'armed' bit */
 		ret = io_reg_modify(PX4IO_PAGE_SETUP, PX4IO_P_SETUP_ARMING, PX4IO_P_SETUP_ARMING_FMU_ARMED, 0);