From f0453b3e0725b6a6c336c5f84f52b579fa1d79f4 Mon Sep 17 00:00:00 2001
From: neilt6 <neilt66@icloud.com>
Date: Wed, 26 Mar 2014 12:00:06 -0600
Subject: [PATCH] Fixed readNB() bug

Fixed a race condition with readNB() in USBHID that caused reports to be
periodically returned empty.
---
 libraries/USBDevice/USBHID/USBHID.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/libraries/USBDevice/USBHID/USBHID.cpp b/libraries/USBDevice/USBHID/USBHID.cpp
index fe097e9b18..0014a5db7c 100644
--- a/libraries/USBDevice/USBHID/USBHID.cpp
+++ b/libraries/USBDevice/USBHID/USBHID.cpp
@@ -59,6 +59,9 @@ bool USBHID::readNB(HID_REPORT *report)
     uint32_t bytesRead = 0;
     bool result;
     result = USBDevice::readEP_NB(EPINT_OUT, report->data, &bytesRead, MAX_HID_REPORT_SIZE);
+    // if readEP_NB did not succeed, does not issue a readStart
+    if (!result)
+        return false;
     report->length = bytesRead;
     if(!readStart(EPINT_OUT, MAX_HID_REPORT_SIZE))
         return false;