USBDevice: clearHalt() method

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.

The clearHalt() method of the USBDevice interface returns a promise that resolves when a halt condition is cleared. A halt condition is when a data transfer to or from the device has a status of 'stall', which requires the web page (the host system, in USB terminology) to clear that condition. See the for details.

Syntax

js
clearHalt(direction, endpointNumber)

Parameters

direction

Indicates whether the devices input or output should be cleared. Valid values are 'in' or 'out'.

endpointNumber

Indicates the number of the endpoint to clear. The promise will reject if an invalid endpoint is supplied.

Return value

A promise.

Examples

The following example shows how to test for and clear a 'stall' condition in the result of a data transfer.

Note: What data can be passed to a USB device and how it is passed is particular and unique to each device.

js
while (true) {
  let result = await data.transferIn(1, 6);

  if (result.data && result.data.byteLength === 6) {
    console.log(`Channel 1: ${result.data.getUint16(0)}`);
    console.log(`Channel 2: ${result.data.getUint16(2)}`);
    console.log(`Channel 5: ${result.data.getUint16(4)}`);
  }

  if (result.status === "stall") {
    console.warn("Endpoint stalled. Clearing.");
    await device.clearHalt("in", 1);
  }
}

Specifications

Specification
WebUSB API
# ref-for-dom-usbdevice-clearhalt①

Browser compatibility

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