From 96f50b7cd72987c2598f782febcc5b559c315215 Mon Sep 17 00:00:00 2001
From: Jonathan Challinger <mr.challinger@gmail.com>
Date: Tue, 7 Oct 2014 07:01:15 -0700
Subject: [PATCH] Copter: add throttle_zero state

---
 ArduCopter/ArduCopter.pde |  1 +
 ArduCopter/radio.pde      | 17 ++++++++++++++---
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/ArduCopter/ArduCopter.pde b/ArduCopter/ArduCopter.pde
index 784e48bb64..f8bedf1c40 100644
--- a/ArduCopter/ArduCopter.pde
+++ b/ArduCopter/ArduCopter.pde
@@ -390,6 +390,7 @@ static union {
         uint8_t motor_test          : 1; // 16  // true if we are currently performing the motors test
         uint8_t initialised         : 1; // 17  // true once the init_ardupilot function has completed.  Extended status to GCS is not sent until this completes
         uint8_t land_complete_maybe : 1; // 18  // true if we may have landed (less strict version of land_complete)
+        uint8_t throttle_zero       : 1; // 19  // true if the throttle stick is at zero, debounced
     };
     uint32_t value;
 } ap;
diff --git a/ArduCopter/radio.pde b/ArduCopter/radio.pde
index cce257ccd2..93a537785b 100644
--- a/ArduCopter/radio.pde
+++ b/ArduCopter/radio.pde
@@ -74,11 +74,15 @@ void output_min()
     motors.output_min();
 }
 
+#define THROTTLE_ZERO_DEBOUNCE_TIME_MS 400
 static void read_radio()
 {
-    static uint32_t last_update = 0;
+    static uint32_t last_update_ms = 0;
+    static uint32_t last_nonzero_throttle_ms = 0;
+    uint32_t tnow_ms = millis();
+
     if (hal.rcin->new_input()) {
-        last_update = millis();
+        last_update_ms = tnow_ms;
         ap.new_radio_frame = true;
         uint16_t periods[8];
         hal.rcin->read(periods,8);
@@ -93,6 +97,13 @@ static void read_radio()
         g.rc_7.set_pwm(periods[6]);
         g.rc_8.set_pwm(periods[7]);
 
+        if (g.rc_3.control_in != 0) {
+            last_nonzero_throttle_ms = tnow_ms;
+            ap.throttle_zero = false;
+        } else if (tnow_ms - last_nonzero_throttle_ms > THROTTLE_ZERO_DEBOUNCE_TIME_MS) {
+            ap.throttle_zero = true;
+        }
+
         // read channels 9 ~ 14
         for (uint8_t i=8; i<RC_MAX_CHANNELS; i++) {
             if (RC_Channel::rc_channel(i) != NULL) {
@@ -108,7 +119,7 @@ static void read_radio()
         // update output on any aux channels, for manual passthru
         RC_Channel_aux::output_ch_all();
     }else{
-        uint32_t elapsed = millis() - last_update;
+        uint32_t elapsed = tnow_ms - last_update_ms;
         // turn on throttle failsafe if no update from the RC Radio for 500ms or 2000ms if we are using RC_OVERRIDE
         if (((!failsafe.rc_override_active && (elapsed >= FS_RADIO_TIMEOUT_MS)) || (failsafe.rc_override_active && (elapsed >= FS_RADIO_RC_OVERRIDE_TIMEOUT_MS))) &&
             (g.failsafe_throttle && motors.armed() && !failsafe.radio)) {