PORTS Forum

Ports and Interfaces => USB => Topic started by: kberisso on October 27, 2014, 09:59:55 pm

Title: Win 8.1 and USB HID
Post by: kberisso on October 27, 2014, 09:59:55 pm

I was hoping to get some help (and maybe some education) on talking to USB HID devices with the new Win 8.1 System.Devices.HumanInterfaceDevice namespace. I am trying to connect to a device via the "endpoints" instead of via reports... first, what is the difference. I have been looking and can't quite make out what the differences. And more importantly, how do I communicate to the device? I have used your sample code in the past to talk to the device, and am now trying to upgrade the apps to the newer Windows 8.1 Store Apps.

Thanks

Kevin

Title: Re: Win 8.1 and USB HID
Post by: Jan Axelson on October 27, 2014, 10:30:15 pm

The documentation here:

http://msdn.microsoft.com/en-us/library/windows/apps/bg182882.aspx#one

says:

Apps retrieve data from a HID device by using input reports.

and gives this example:

var inputReport = await DeviceList.Current.CurrentDevice.GetInputReportAsync(SuperMutt.ReadWriteBuffer.ReportId);

Can you give an example of what you're attempting?

Title: Re: Win 8.1 and USB HID
Post by: kberisso on October 27, 2014, 10:49:48 pm

Thanks for the quick reply.

I have been to the site and can "see" the USB device (it is an RFID reader that is set up as a USB HID device with the following info:

Device Descriptor:
bcdUSB:             0x0110
bDeviceClass:         0xFF
bDeviceSubClass:      0x00
bDeviceProtocol:      0xFF
bMaxPacketSize0:      0x08 (8)
bcdDevice:          0x0001
bNumConfigurations:   0x01

ConnectionStatus: DeviceConnected
Current Config Value: 0x01
Device Bus Speed:     Full
Device Address:       0x04
Open Pipes:              2

Endpoint Descriptor:
bEndpointAddress:     0x01  OUT
Transfer Type:   Interrupt
wMaxPacketSize:     0x0040 (64)
bInterval:            0x01

Endpoint Descriptor:
bEndpointAddress:     0x82  IN
Transfer Type:   Interrupt
wMaxPacketSize:     0x0040 (64)
bInterval:            0x01

Configuration Descriptor:
wTotalLength:       0x0029
bNumInterfaces:       0x01
bConfigurationValue:  0x01
iConfiguration:       0x00
bmAttributes:         0xC0 (Bus Powered Self Powered )
MaxPower:             0xFA (500 Ma)

Interface Descriptor:
bInterfaceNumber:     0x00
bAlternateSetting:    0x00
bNumEndpoints:        0x02
bInterfaceClass:      0x03 (HID)
bInterfaceSubClass:   0x00
bInterfaceProtocol:   0x00
iInterface:           0x00

HID Descriptor:
bcdHID:             0x0111
bCountryCode:         0x00
bNumDescriptors:      0x01
bDescriptorType:      0x22
wDescriptorLength:  0x0062

Endpoint Descriptor:
bEndpointAddress:     0x01  OUT
Transfer Type:   Interrupt
wMaxPacketSize:     0x0040 (64)
bInterval:            0x01

Endpoint Descriptor:
bEndpointAddress:     0x82  IN
Transfer Type:   Interrupt
wMaxPacketSize:     0x0040 (64)
bInterval:            0x01

I am trying to send it a command (4349544DFF130000000000000000) that is 16 bytes long.

What I don't get (and never really understood even with the WinXP/7 version of my program) is how the endpoints relate to the reports. I am assuming that the "In" endpoint is the input report and the "Out" endpoint is the output report, but if that is the case, I can't seem to get my command string into the report

I tried:

                    var output = myDevice.CreateOutputReport();
                    var dataWriter = new DataWriter();
                    dataWriter.WriteBytes(myData);
                    dataWriter.DetachBuffer();

                    uint result = await myDevice.SendOutputReportAsync(output);

but always get a Access Denied error when I hit the last line (where I send the report). I know that I have a good device and have confirmed that myDevice is valid (or at least I can see a VID/PID and other related info).

Thanks

Kevin