From c3d21a457ff10185a52940972640ab0dda7e3f5b Mon Sep 17 00:00:00 2001
From: Randy Mackay <rmackay9@yahoo.com>
Date: Tue, 28 May 2013 21:50:31 +0900
Subject: [PATCH] Copter: add pre-arm board voltage check

Copter will not arm unless board voltage is over 4.5V
---
 ArduCopter/config.h   | 4 ++++
 ArduCopter/motors.pde | 8 ++++++++
 2 files changed, 12 insertions(+)

diff --git a/ArduCopter/config.h b/ArduCopter/config.h
index 4ce6654c95..62aae16f7c 100644
--- a/ArduCopter/config.h
+++ b/ArduCopter/config.h
@@ -382,6 +382,10 @@
  # define HIGH_DISCHARGE                 1760
 #endif
 
+#ifndef BOARD_VOLTAGE_MIN
+ # define BOARD_VOLTAGE_MIN             4500        // min board voltage in milli volts for pre-arm checks
+#endif
+
 // Battery failsafe
 #ifndef FS_BATTERY
  # define FS_BATTERY              DISABLED
diff --git a/ArduCopter/motors.pde b/ArduCopter/motors.pde
index 66c591b892..dffbc14877 100644
--- a/ArduCopter/motors.pde
+++ b/ArduCopter/motors.pde
@@ -264,6 +264,14 @@ static void pre_arm_checks(bool display_failure)
     }
 #endif
 
+    // check board voltage
+    if(board_voltage() < BOARD_VOLTAGE_MIN) {
+        if (display_failure) {
+            gcs_send_text_P(SEVERITY_HIGH,PSTR("PreArm: Low Board Voltage"));
+        }
+        return;
+    }
+
     // if we've gotten this far then pre arm checks have completed
     ap.pre_arm_check = true;
 }