From 18e811b4ee1c8d9149631d474b37940c34518703 Mon Sep 17 00:00:00 2001
From: Robert Fisk <robert_fisk@fastmail.fm>
Date: Thu, 28 Apr 2016 21:37:34 +1200
Subject: [PATCH] HID report parser now handles collections.

---
 Downstream/Inc/downstream_hid.h |  4 ++++
 Downstream/Src/downstream_hid.c | 17 +++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/Downstream/Inc/downstream_hid.h b/Downstream/Inc/downstream_hid.h
index 033392e..a9f2fd2 100644
--- a/Downstream/Inc/downstream_hid.h
+++ b/Downstream/Inc/downstream_hid.h
@@ -25,6 +25,10 @@
 #define HID_ITEM_USAGE_PAGE_BUTTON  0x09
 #define HID_ITEM_USAGE_PAGE_DESKTOP 0x01
 
+#define HID_ITEM_COLLECTION         0xA1
+#define HID_ITEM_COLLECTION_PHYS    0x00
+#define HID_ITEM_END_COLLECTION     0xC0
+
 #define HID_ITEM_USAGE              0x09        //'local' usage
 #define HID_ITEM_USAGE_X            0x30
 #define HID_ITEM_USAGE_Y            0x31
diff --git a/Downstream/Src/downstream_hid.c b/Downstream/Src/downstream_hid.c
index 095ab1c..c383344 100644
--- a/Downstream/Src/downstream_hid.c
+++ b/Downstream/Src/downstream_hid.c
@@ -106,6 +106,23 @@ HAL_StatusTypeDef Downstream_HID_Mouse_ParseReportDescriptor(void)
             wheelUsageIndex = 0xFF;
             break;
 
+        case HID_ITEM_COLLECTION:               //Physical collections also clear the usage index...
+            if (ItemData == HID_ITEM_COLLECTION_PHYS)
+            {
+                currentUsageIndex = 0;
+                xUsageIndex = 0xFF;
+                yUsageIndex = 0xFF;
+                wheelUsageIndex = 0xFF;
+            }
+            break;
+
+        case HID_ITEM_END_COLLECTION:           //...and so do collection ends
+            currentUsageIndex = 0;
+            xUsageIndex = 0xFF;
+            yUsageIndex = 0xFF;
+            wheelUsageIndex = 0xFF;
+            break;
+
         case HID_ITEM_USAGE:
             switch (ItemData)
             {