HID device losing reports

Question

1.00/5 (1 vote)

See more:

Hello,
my HID device sends IN report every 200 msec. I call THid::Execute every 10 msec. However, I lose 20% of IN reports. Input buffer count is 512.

When I increase timeout value for WaitForSingleObject I lose less reports. But I want the WaitForSingleObject function to work with zero timeout.

C++

void THid::Execute(void)
// Execute device
{
THidReportExt ReportExt;
HANDLE     Event;
OVERLAPPED Overlapped;
DWORD ReadBytes;

   if(!Handle) {
      return;
   }

   Event = CreateEvent(NULL, TRUE, FALSE, NULL);
   Overlapped.hEvent = Event;
   Overlapped.Offset = 0;
   Overlapped.OffsetHigh = 0;

   while(true) {
      if(!ReadFile(Handle, &ReportExt, Capabilities.InputReportByteLength, &ReadBytes, &Overlapped)) {
         if(GetLastError() != ERROR_IO_PENDING) {
            return;
         }
         DWORD Result = WaitForSingleObject(Event, 0);
         if(Result == WAIT_TIMEOUT || Result == WAIT_ABANDONED) {
            CancelIo(Handle);
            return;
         }
         if(Result != WAIT_OBJECT_0) {
            return;
         }
         if(!GetOverlappedResult(Handle, &Overlapped, &ReadBytes, FALSE)) {
            return;
         }
      }
      if(ReadBytes != (DWORD)Capabilities.InputReportByteLength) {
         return;
      }
      // call some callback
   }
} // Execute

This is how I open the file:

C++

Handle = CreateFile(Path,
      GENERIC_WRITE | GENERIC_READ,
      FILE_SHARE_WRITE | FILE_SHARE_READ,
      NULL,
      OPEN_EXISTING,
      FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED,
      NULL);

Posted 21-Apr-14 10:28am

gaminn

Updated 21-Apr-14 10:29am

v2

Add a Solution

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Sergey Alexandrovich Kryukov · Answer 1 · 2014-04-21T10:55:00

Solution 1

Using WaitForSingleObject with zero timeout is apparent nonsense. Timeout should be more than zero, considerably more; and infinite value is also possible.

I don't know if I should explain to you how to use event handles (event objects) and their purpos, but you apparently have no clue, at the moment. Let's do this: start with reading the standard MSDN documentation on them, and, if you still not clear about this topic, ask some further questions.

—SA

Posted 21-Apr-14 10:55am

Sergey Alexandrovich Kryukov

Comments

gaminn 22-Apr-14 11:24am

I really can't see anything bad about my code (apart from not closing event handle in Execute function). I'm creating event, passing it to ReadFile function and then waiting zero miliseconds for the event to be signaled. I don't want my Execute function to block, this is the reason for zero ms wait.

I would appreciate your explanation and help.

Sergey Alexandrovich Kryukov 22-Apr-14 12:32pm

All wrong. You simply have no clue what the event is for. It's for keeping a thread in a wait state in some other thread. If you wait zero time, event is not needed at all.
—SA

gaminn 22-Apr-14 12:53pm

I understand events. I know it's redundant to use event in my case. I think, that my problem comes from calling CancelIo().

My question is how to read from HID without blocking my thread - if there is an IN report in buffer, then return it, otherwise return some error.

Sergey Alexandrovich Kryukov 22-Apr-14 13:29pm

You just have proven the opposite, very clearly. No, you don't. Sorry, nothing to discuss here. Study the subject matter.
—SA