Timing issue when sending multilple reports to a device

[chedges]

Hi Roman,

I've run into a problem when sending multiple reports to a device in fast succession. If you remember, I am writing to a printer and I need to send the data in 256byte reports.

I have found a problem when sending reports (The test I'm doing requires 4 reports of the same reportId) with no delay between them causes the printed output
to be corrupted. When I put a 100m/s pause between the reports the printing works fine.
I repeatedly check to see if the device is busy / cannot recieve data as I am writing the reports and I am 100% confident that the device is not going into a busy state.

I sent a demo app to the manufacturer and they were able to perform a USB trace to debug the problem. It seems that bytes are being lost when sending reports without a pause . My best guess is nrHID has not completed when it is called upon to transmit again and some of the bytes are not reaching the printer.

I don't want to have to use 100m/s delay between each report as this will badly effect print performance. Is there any way of determining if nrHID has written all the data and can send more? I presume this is / should be handled internally by the component

Thanks for your help

Chris Hedges

[Roman Novgorodov]

Hello Chris

I remember that you are using TnrHid.SendData() method for send reports. This function is asynchronous.

You can try to replace it by TnrHid.WriteReport() call.

Roman Novgorodov
DeepSoftware.Com

[chedges]

Hi Roman,

I used to use the WriteReport method but when I upgraded to the 8.21 version it stopped working for me, hence the switch to SendData.
I've tried using HidD_SetOutputReport and that doesn't seem to work either. What changed in the upgrade that stopped the WriteReport working?

thanks

Chris

[Roman Novgorodov]

Hello

Yes you are right.
The WriteReport() method was changed.
It uses HidD_SetOutputReport() API call now.

But your device works strange: it works good with HidD_GetInputReport() and it should support HidD_SetOutputReport() correctly too.

I will think more.

Do you remember, you showed me a VB sample that is read a HID report?
Do you have such sample from printer manufacturer that writes report?

Please try it to test device and be sure that device is working properly.

Roman Novgorodov
DeepSoftware.Com

[chedges]

Hi Roman,

Here is the VB code used to write to the printer. This works ok.



Public Sub Transmit(text_data As String)
       
Dim NumberOfBytesWritten As Long
Dim SendBuffer() As Byte
Dim i, Count As Integer
Dim pData As Long

ReDim SendBuffer(0 To (Capabilities.OutputReportByteLength - 1)) As Byte

    ' Check the USB pointer for readiness
    If WriteHandle = 0 Then
           
        Display_Text ("Unable to write to Boca Systems USB Printer.  Invalid write handle.")
       
    Else
           
        'Display_Text ("A Boca Systems USB Printer has been located")
           
        'This string needs to be converted into a byte array of ascii
        'integers to send to the printer. Convert will also initilize
        'ptr_buffer and Str_Size.
        Count = Len(text_data)
        Call Convert(text_data)
        'For i = 1 To Count
        '    SendBuffer(i) = Asc(Mid(text_data, i, 1))
        'Next i
       
        'The first byte is the Report ID
        For i = 0 To Capabilities.OutputReportByteLength - 1
            SendBuffer(i) = 0
        Next i
        For i = 1 To Capabilities.OutputReportByteLength - 1
            SendBuffer(i) = text(i - 1) 'text_data(i - 1)
        Next i
       
        'SendBuffer(0) = 0
        'For i = 1 To Count
        '    SendBuffer(i) = text(i - 1)
        'Next i

        'Display_Text ("string size = " + str(Str_Size))
           
        'Write converted text string and read for status response
        'Need to convert these to functions to receive return values as Longs???
        NumberOfBytesWritten = 0

        Result = WriteFile _
        (WriteHandle, _
        SendBuffer(0), _
        CLng(Capabilities.OutputReportByteLength), _
        NumberOfBytesWritten, _
        0)

    End If

End Sub

[Roman Novgorodov]

Hello Chris

The old version of TnrHid.WriteReport() used WriteFile call :-).
Now this method uses HidD_SetOutputReport() function.

Your device is real strange.
It uses HidD_GetInputReport() for read HID reports (and does not work with ReadFile())
At same time your printer wants WriteFile() for send report and does not support HidD_SetFeature() function.

OK.
We will think something more and will add new methods into TnrHid component.

Whilst I recommend you to call WriteFile like in your VB sample with TnrHid.Handle parameter.

Roman Novgorodov
DeepSofware.Com

[chedges]

Thanks for you help again Roman,

You have to love a challenge, especially when it's your first HID project ;)
Nothing is ever easy!

[chedges]

Hi Roman,

I'm getting a wierd Error 87 (Parameter is incorrect) when using the WriteFile method.
Have you seen this error before as the method itself looks pretty straightforward?

procedure TForm6.NewHIDWrite(Data : String);
var
  ToWrite, NumberOfBytesWritten: Cardinal;
  cnt : integer;
  Report : Array of Byte;
begin
    ToWrite := nrHid1.HidDevice.OutputReportLength;
    SetLength(Report, ToWrite);

    //init the buffer
    for cnt  := 0 to ToWrite - 1 do
      Report[cnt] := 0;

    //fill it!
    for cnt := 1 to Length(Data) do
      Report[cnt] := Ord(Data[cnt]);

    NumberOfBytesWritten := 0;
    if not WriteFile(nrHID1.Handle, Report, ToWrite, NumberOfBytesWritten, 0) then
      ShowMessage(SysErrorMessage(GetLastError));
end;

[Roman Novgorodov]

Hello Chris

You can try the following:

WriteFile(nrHID1.Handle, Report[0], ToWrite, NumberOfBytesWritten, 0)

But usual we are using Pointer or PChar variable for second parameter of this function.

By the way the new version of nrComm Lib is released.
It has some changes - new methods:

    function ReadReport(const pcReport:pointer; const ReportSize:cardinal):boolean;
    function WriteReport(const pcReport: pointer; const ReportSize:cardinal):boolean;

    function GetInputReport(const pcReport:pointer; const ReportSize:cardinal):boolean;
    function SetOutputReport(const pcReport: pointer; const ReportSize:cardinal):boolean;

Please ask me over email and you will receive latest release.

Roman Novgorodov
DeepSoftware.Com

[chedges]

Thanks Roman,

The new version of WriteReport seems to be working perfectly

Thanks again for helping me out :)

Chris.