Problem reading data from an USB device

[makTSPL]

Dear All,
I am developing an application in C#. This application communicates with Garmin Forerunner device. I have developed a demo for it, which shows Device software version. but I am not able to get Device history Data. What should I pass for getting history data.

Below is the code sample which I am using for fetching device information:

// Product data
byte[] theProductPacket = new byte[] { 20, 0, 0, 0, 254, 0, 0, 0, 0, 0, 0, 0 };

byte[] thePacket = new byte[] { };

// For initializing device
initDevice();

//Checking for device availability
if (gHandle.ToInt32() == 0)
{
return "No Device Found";
}

// Sending Packet for starting asession
SendPackets(theProductPacket);

// Infinite loop for Data retreival
for (; ; )
{
// Getting one by one Packets
thePacket = GetPackets2();
if (Convert.ToInt32(thePacket.GetValue(0).ToString()) == 20 && Convert.ToInt32(thePacket.GetValue(4).ToString()) == 255)
{
break;
}
}

string Data = System.Text.ASCIIEncoding.ASCII.GetString(thePacke t, 4, thePacket.Length - 4);

bool bSuccess = CloseHandle(gHandle);


I am sure that I have to change following:
// Product data
byte[] theProductPacket = new byte[] { 20, 0, 0, 0, 254, 0, 0, 0, 0, 0, 0, 0 };

I am not asking for providing code, but if anyone can post approach for it then it will be highly appreciated.