USBDevice: opened property

Limited availabilitySecure contextAvailable in workers

The opened read only property of the USBDevice interface indicates whether a session has been started with a paired USB device. A device must be opened before it can be controlled by a web page.

Value

A Boolean.

Examples

This example is for a hypothetical USB device with a multi-colored LED. It shows how to test that a device is open before calling controlTransferOut to set a specified LED color.

[!NOTE] What data can be passed to a USB device and how it is passed is particular and unique to each device.

async function setDeviceColor(usbDevice, r, g, b) {
  if (device.opened) {
    // This hypothetical USB device requires that the data passed to
    // it be in a Uint8Array.
    const payload = new Uint8Array([r, g, b]);

    await usbDevice.controlTransferOut(
      {
        requestType: "vendor",
        recipient: "device",
        request: 1,
        value: 0,
        index: 0,
      },
      payload,
    );
  }
}

Specifications

Browser compatibility