From 90b74f5bab334c07e2c81168276ba238d3c80f06 Mon Sep 17 00:00:00 2001
From: Craig Elder <Craig@3Drobotics.com>
Date: Mon, 10 Sep 2012 08:07:50 +1000
Subject: [PATCH] APM_RC: fixed noisy PWM output on startup for APM2

This reduces the number of rubbish pulses on the APM2 PWM output pins
on startup, which should help with booting some cheaper ESCs.

Thanks to Randy for the idea!
---
 libraries/APM_RC/APM_RC_APM2.cpp | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/libraries/APM_RC/APM_RC_APM2.cpp b/libraries/APM_RC/APM_RC_APM2.cpp
index 472358c9e3..811d16c181 100644
--- a/libraries/APM_RC/APM_RC_APM2.cpp
+++ b/libraries/APM_RC/APM_RC_APM2.cpp
@@ -81,8 +81,12 @@ APM_RC_APM2::APM_RC_APM2()
 void APM_RC_APM2::Init( Arduino_Mega_ISR_Registry * isr_reg )
 {
     // --------------------- TIMER1: OUT1 and OUT2 -----------------------
+    digitalWrite(12,HIGH);  // pulling high before changing to output avoids a momentary drop of the pin to low because the ESCs have a pull-down resistor it seems
+    digitalWrite(11,HIGH);
     pinMode(12,OUTPUT); // OUT1 (PB6/OC1B)
     pinMode(11,OUTPUT); // OUT2 (PB5/OC1A)
+    digitalWrite(12,HIGH);  // pulling high before changing to output avoids a momentary drop of the pin to low because the ESCs have a pull-down resistor it seems
+    digitalWrite(11,HIGH);
 
     // WGM: 1 1 1 0. Clear Timer on Compare, TOP is ICR1.
     // CS11: prescale by 8 => 0.5us tick
@@ -93,9 +97,15 @@ void APM_RC_APM2::Init( Arduino_Mega_ISR_Registry * isr_reg )
     OCR1B = 0xFFFF;
 
     // --------------- TIMER4: OUT3, OUT4, and OUT5 ---------------------
+    digitalWrite(8,HIGH);
+    digitalWrite(7,HIGH);
+    digitalWrite(6,HIGH);
     pinMode(8,OUTPUT); // OUT3 (PH5/OC4C)
     pinMode(7,OUTPUT); // OUT4 (PH4/OC4B)
     pinMode(6,OUTPUT); // OUT5 (PH3/OC4A)
+    digitalWrite(8,HIGH);
+    digitalWrite(7,HIGH);
+    digitalWrite(6,HIGH);
 
     // WGM: 1 1 1 0. Clear Timer on Compare, TOP is ICR4.
     // CS41: prescale by 8 => 0.5us tick
@@ -107,9 +117,15 @@ void APM_RC_APM2::Init( Arduino_Mega_ISR_Registry * isr_reg )
     ICR4 = 40000; // 0.5us tick => 50hz freq
 
     //--------------- TIMER3: OUT6, OUT7, and OUT8 ----------------------
+    digitalWrite(3,HIGH);
+    digitalWrite(2,HIGH);
+    digitalWrite(5,HIGH);
     pinMode(3,OUTPUT); // OUT6 (PE5/OC3C)
     pinMode(2,OUTPUT); // OUT7 (PE4/OC3B)
     pinMode(5,OUTPUT); // OUT8 (PE3/OC3A)
+    digitalWrite(3,HIGH);
+    digitalWrite(2,HIGH);
+    digitalWrite(5,HIGH);
 
     // WGM: 1 1 1 0. Clear timer on Compare, TOP is ICR3
     // CS31: prescale by 8 => 0.5us tick
@@ -123,8 +139,13 @@ void APM_RC_APM2::Init( Arduino_Mega_ISR_Registry * isr_reg )
     //--------------- TIMER5: PPM INPUT, OUT10, and OUT11 ---------------
     // Init PPM input on Timer 5
     pinMode(48, INPUT); // PPM Input (PL1/ICP5)
+
+    digitalWrite(45,HIGH);
+    digitalWrite(44,HIGH);
     pinMode(45, OUTPUT); // OUT10 (PL4/OC5B)
     pinMode(44, OUTPUT); // OUT11 (PL5/OC5C)
+    digitalWrite(45,HIGH);
+    digitalWrite(44,HIGH);
 
     // WGM: 1 1 1 1. Fast PWM, TOP is OCR5A
     // COM all disabled.