Reading first byte of feature report on Mk2 differs from Mk1 devices

[jrotello]

I am finding that on the Mk2 devices, the report id does not come back in the first byte as expected. Mk1 devices work as expected though. Running the following code sample on a machine with both a Mk1 and a Mk2 device will show the issue. On the Mk2 device, I would expect the first byte of the read report to have a value of 0x01 as it does for the Mk1 devices. While my example code is using the HidSharp nuget package, the same results occur when using the HidLibrary nuget package. Is this difference expected between the Mk1 and Mk2 devices?

I also noticed that both the Mk1 and Mk2 devices report a max feature report length of 9 bytes, but your documentation indicates the length to be 8 bytes. Is the extra byte reserved for future use? On Windows (.NET), the HidSharp library forces you to use 9 byte buffers because that is what the device is reporting. The HidLibrary library is not as strict. It will let you write an 8 byte buffer, but always returns 9 bytes.

Neither of these are a huge deal. I'm mainly just trying to better understand how things are working.

Code

// *****  Depends on the HidSharp nuget package  *****

const int ProductId = 0x01ED;
const int VendorId = 0x27B8;

var loader = new HidDeviceLoader();

// Read the pattern value at position 5 for each connected device.
var devices = loader.GetDevices(VendorId, ProductId);
foreach (HidDevice device in devices) {
    Console.WriteLine("{0} [MaxFeatureReportLength: {1}]", device.ProductName, device.MaxFeatureReportLength);

    using(var stream = device.Open()) {
        var hidbuffer = new byte[] { 0x01, (byte)'R', 0, 0, 0, 0, 0, 5, 0};
        Console.WriteLine("Write Feature Report: {0}", String.Join("-", hidbuffer));
        stream.SetFeature(hidbuffer);

        hidbuffer = new byte[device.MaxFeatureReportLength];    
        hidbuffer[0] = 0x01;
        stream.GetFeature(hidbuffer);
        Console.WriteLine("Read Feature Report: {0}", String.Join("-", hidbuffer));
    }   

    Console.WriteLine();
}

Output

blink(1) mk2 [MaxFeatureReportLength: 9]
Write Feature Report: 1-82-0-0-0-0-0-5-0
Read Feature Report: 0-82-0-0-255-0-25-5-0

blink(1) [MaxFeatureReportLength: 9]
Write Feature Report: 1-82-0-0-0-0-0-5-0
Read Feature Report: 1-82-0-0-255-0-25-5-0