From 482ce55d579a56984abb633a3e9d1edf7eddd665 Mon Sep 17 00:00:00 2001
From: Julian Oes <julian@oes.ch>
Date: Thu, 21 Apr 2016 13:32:38 +0200
Subject: [PATCH] px4io: allow 0 as a PWM signal

---
 src/drivers/px4io/px4io.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/drivers/px4io/px4io.cpp b/src/drivers/px4io/px4io.cpp
index ecaf156d7e..383a6d4d0f 100644
--- a/src/drivers/px4io/px4io.cpp
+++ b/src/drivers/px4io/px4io.cpp
@@ -2656,7 +2656,12 @@ PX4IO::ioctl(file *filep, int cmd, unsigned long arg)
 			/* TODO: we could go lower for e.g. TurboPWM */
 			unsigned channel = cmd - PWM_SERVO_SET(0);
 
-			if ((channel >= _max_actuators) || (arg < PWM_LOWEST_MIN) || (arg > PWM_HIGHEST_MAX)) {
+			PX4_INFO("pwm is %d (%d, %d)", arg, PWM_LOWEST_MIN, PWM_HIGHEST_MAX);
+
+			/* PWM needs to be either 0 or in the valid range. */
+			if ((arg != 0) && ((channel >= _max_actuators) ||
+					   (arg < PWM_LOWEST_MIN) ||
+					   (arg > PWM_HIGHEST_MAX))) {
 				ret = -EINVAL;
 
 			} else {