why can't i get report from hid usb device by GetInputReport

Question

In my delphi application, i use TJvHidDevice for writing and reading report from a usb device.

The device info bellows

Bus Type:        USB
Device Type:     Human Interface Device
Power Drawn:     100 milliamps @ 5.0 volts
Endpoint 0:      Type=CTL  Class=03 SubClass=00 Protocol=00 MaxPacket=8
Endpoint 1 OUT:  Type=INT  Class=03 SubClass=00 Protocol=00 MaxPacket=40
Endpoint 2 IN:   Type=INT  Class=03 SubClass=00 Protocol=00 MaxPacket=40
Hardware ID:     USB\Vid_0483&Pid_5750&Rev_0200
Data Read:       572 bytes
Data Written:    384 bytes
Utilization:     100%

It has three endpoints,and it will out put report with endpoint 2 when i send report to it. My codes are

Report structure

TReport = packed record
    ReportID: byte;
    Data: array[0..64] of byte;
end;

Check out Device

procedure TfrmMain.HidDevsDeviceChange(Sender: TObject);
begin
    if HidDevs.CheckOutByID(FHidDev, USB_VID, USB_PID) then
    begin
        FHidDev.NumInputBuffers := 65;
        FHidDev.NumOverlappedBuffers := 65;
        FUsbDevice.Device := FHidDev;
        FHidDev.OnData:=OnRead;
    end;
end;

OnRead Enent

procedure TfrmMain.OnRead(HidDev: TJvHidDevice; ReportID: Byte; const Data: Pointer; Size: Word);
var I: Integer;
    Str: string;
begin
    Str := Format('RD %.2x  ', [ReportID]);
    for I := 0 to Size - 1 do
        Str := Str + Format('%.2x ', [Cardinal(PChar(Data)[I])]);
    AddLog('Received: ');
    SetLogColor(clPurple);
    AddLog(Str, False);
end;

I can write report by

if not FDevice.SetOutputReport(FBuffer, FDevice.Caps.OutputReportByteLength) then

but , after SetOutputReport nothing happens.If i used GetInputReport instead of OnRead, there will be an error : 31 , if use readFile,the application will hang up. why,and what should i do?

Answer 1

The problem has been resolved. It was that , the size of report sent to Application wasn't correct,it was less than the InputReportByteLength of 65 ,so the application wouldn't receive anything.