From 0ca71ba72579af24c653d7f950203d338b9f3c1d Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Tue, 18 Jun 2019 12:57:39 +1000
Subject: [PATCH] AP_HAL: added get_last_armed_change() Util function

---
 libraries/AP_HAL/Util.cpp | 9 ++++++---
 libraries/AP_HAL/Util.h   | 4 ++++
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/libraries/AP_HAL/Util.cpp b/libraries/AP_HAL/Util.cpp
index 8217ae2751..0baf3ab67a 100644
--- a/libraries/AP_HAL/Util.cpp
+++ b/libraries/AP_HAL/Util.cpp
@@ -93,8 +93,11 @@ void AP_HAL::Util::set_hw_rtc(uint64_t time_utc_usec)
 
 void AP_HAL::Util::set_soft_armed(const bool b)
 {
-    soft_armed = b;
-    if (!was_watchdog_reset()) {
-        persistent_data.armed = b;
+    if (b != soft_armed) {
+        soft_armed = b;
+        last_armed_change_ms = AP_HAL::millis();
+        if (!was_watchdog_reset()) {
+            persistent_data.armed = b;
+        }
     }
 }
diff --git a/libraries/AP_HAL/Util.h b/libraries/AP_HAL/Util.h
index 8fd9e77914..aeb10d82cf 100644
--- a/libraries/AP_HAL/Util.h
+++ b/libraries/AP_HAL/Util.h
@@ -14,6 +14,9 @@ public:
     void set_soft_armed(const bool b);
     bool get_soft_armed() const { return soft_armed; }
 
+    // return the time that the armed state last changed
+    uint32_t get_last_armed_change() const { return last_armed_change_ms; };
+
     // return true if the reason for the reboot was a watchdog reset
     virtual bool was_watchdog_reset() const { return false; }
 
@@ -158,4 +161,5 @@ protected:
     // we start soft_armed false, so that actuators don't send any
     // values until the vehicle code has fully started
     bool soft_armed = false;
+    uint32_t last_armed_change_ms;
 };