I am trying to allow a POS web app to print directly to a StarMicronics (or any receipt printer, for that matter) using the Chrome webusb API.
I am using the example here almost exactly except I have modified the vendorId filter to the Vendor ID of StarMicronics. I have also tried it with a completely empty filter. It works great on the Mac computers I have tested it on, but the problem is on Windows.
When I click the print button, Chrome opens up the connection window, my device is listed and I can select it and click Connect. So navigator.usb.getDevices() is working great. When I refresh the window, after having connected the website to the device, Chrome finds the device again with no problem.
The problem comes when I try to do device.open(). I get this error in the console: DOMException: Access Denied. From this point, I can't do either device.selectConfiguration() or device.claimInterface() because I get the error that the device must first be opened, obviously.
I have enabled all the flags I know of in Chrome:
#enable-experimental-web-platform-features
#enable-webusb
#new-usb-backend
But none of this has helped. I have also tried using other printers, such as an HP deskjet and a Dymo Label Writer all with the same resulting error message that access is denied.
Again, it is working fine on Macs.
Any help on this would be greatly appreciated.
You get the "Access Denied" error on Windows because there is already a driver that has claimed the device. The Windows driver model requires that the "winusb.sys" driver be loaded for any device that will be accessed by a userspace application like Chrome.
See my answer to this earlier question about smartcard readers which encounter the same difficulty on Windows.
来源：https://stackoverflow.com/questions/47143148/webusb-access-denied-trying-to-open-printer-on-windows