How to to read input stream from Magnetic stripe reader with keyboard support in Windows 10 universal app - usb

Question

We have tried the approach suggested at:
https://msdn.microsoft.com/en-us/library/windows/hardware/dn312121(v=vs.85).aspx
https://msdn.microsoft.com/en-us/library/windows/hardware/dn303343(v=vs.85).aspx
We are able to find out list of all the magneticDevices using below code snippet
var magneticDevices = await DeviceInformation.FindAllAsync(aqsFilter);
but we are not able to get HidDevice object from the below code. It is giving null.
HidDevice device = await HidDevice.FromIdAsync(magneticDevices[0].Id
We have also set device capabilities in the app manifest file like below.
<DeviceCapability Name="humaninterfacedevice">
<Device Id="vidpid:0ACD 0520">
<Function Type="usage:0001 0006"/>
</Device>
</DeviceCapability>
<DeviceCapability Name="usb">
<Device Id="vidpid:0ACD 0520">
<Function Type="winUsbId:4d1e55b2-f16f-11cf-88cb-001111000030"/>
</Device>
</DeviceCapability>
Code for the complete Function
private async Task<bool> HasCardReader()
{
bool hasCardReader = false;
ushort usagePage = 0x0001;
ushort usageId = 0x0006;
ushort vendorId = 0x0ACD;
ushort productId = 0x0520;
var aqsFilter = HidDevice.GetDeviceSelector(usagePage, usageId, vendorId, productId);
var magneticDevices = await DeviceInformation.FindAllAsync(aqsFilter);
try
{
if (magneticDevices != null && magneticDevices.Count > 0)
{
HidDevice device = await HidDevice.FromIdAsync(magneticDevices[0].Id, Windows.Storage.FileAccessMode.Read);
inputReportEventHandler = new TypedEventHandler<HidDevice, HidInputReportReceivedEventArgs>(this.OnInputReportEvent);
device.InputReportReceived += inputReportEventHandler;
var watcher = DeviceInformation.CreateWatcher(aqsFilter);
watcher.Added += WatcherAdded;
watcher.Removed += WatcherRemoved;
watcher.Start();
hasCardReader = true;
}
else
{
}
}
catch (Exception ex)
{
Logging.LoggingSessionScenario.LogMessageAsync(ex.Message, LoggingLevel.Error);
}
return hasCardReader;
}

Answer 1

There are several reasons for the null return value, but I don't think there is something wrong with your code, since you can find the device by calling FindAllAsync. I will suggest you to troubleshoot this issue using this official HIDDevice sample on GitHub.
I successfully connected to my external hid device with that sample by changing the vid & pid & usagepage & usageid to my device.
In EventHandlerForDevice.cs, find the function OpenDeviceAsync, and you will notice the following possible reasons when null is returned by FromIdAsync.
else
{
successfullyOpenedDevice = false;
notificationStatus = NotifyType.ErrorMessage;
var deviceAccessStatus = DeviceAccessInformation.CreateFromId(deviceInfo.Id).CurrentStatus;
if (deviceAccessStatus == DeviceAccessStatus.DeniedByUser)
{
notificationMessage = "Access to the device was blocked by the user : " + deviceInfo.Id;
}
else if (deviceAccessStatus == DeviceAccessStatus.DeniedBySystem)
{
// This status is most likely caused by app permissions (did not declare the device in the app's package.appxmanifest)
// This status does not cover the case where the device is already opened by another app.
notificationMessage = "Access to the device was blocked by the system : " + deviceInfo.Id;
}
else
{
// Most likely the device is opened by another app, but cannot be sure
notificationMessage = "Unknown error, possibly opened by another app : " + deviceInfo.Id;
}
}
Have a try with that sample(Scenario1) and change the ids in both appxmanifest and SampleConfiguration.cs(class Device). If you cannot see your device in the device list, that means the configuration is incorrect for your device.