From f9b7416df0dd0465d1ddcdeb5e148486e32f4563 Mon Sep 17 00:00:00 2001
From: Robert Fisk <robert_fisk@fastmail.fm>
Date: Sun, 8 May 2016 22:37:54 +1200
Subject: [PATCH] Sleep instead of busy-wait, approx 50% power reduction!

---
 Downstream/Src/main.c | 11 +++++++++++
 Upstream/Src/main.c   |  3 ++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/Downstream/Src/main.c b/Downstream/Src/main.c
index f64aa9a..a13a160 100644
--- a/Downstream/Src/main.c
+++ b/Downstream/Src/main.c
@@ -52,6 +52,8 @@ void CheckFirmwareMatchesHardware(void);
 
 int main(void)
 {
+    uint32_t iterationCount = 0;
+
     //First things first!
     DisableFlashWrites();
     CheckFirmwareMatchesHardware();
@@ -74,6 +76,15 @@ int main(void)
         USB_Host_Process();
         Downstream_SPIProcess();
         Downstream_PacketProcessor_CheckNotifyDisconnectReply();
+
+        //Some USB host state transitions take 3 iterations to fully apply.
+        //We'll be generous and give it 5 before sleeping.
+        iterationCount++;
+        if (iterationCount > 4)
+        {
+            iterationCount = 0;
+            __WFI();                //sleep time!
+        }
     }
 }
 
diff --git a/Upstream/Src/main.c b/Upstream/Src/main.c
index d6886c2..b640d54 100755
--- a/Upstream/Src/main.c
+++ b/Upstream/Src/main.c
@@ -78,11 +78,12 @@ int main(void)
 
     while (1)
     {
-
+        __WFI();            //sleep time!
     }
 }
 
 
+
 void DisableFlashWrites(void)
 {
     //Disable flash writes until the next reset