Web/API/USBDevice/clearHalt

This is an experimental technologyCheck the Browser compatibility table carefully before using this in production.

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 tranfer 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

var promise = USBDevice.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.

Example

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

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

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	Status	Comment
WebUSBThe definition of 'clearHalt()' in that specification.	Draft	Initial definition.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`clearHalt` Experimental'	Chrome Full support 61	Edge Full support 79	Firefox No support No	IE No support No	Opera Full support 48	Safari No support No	WebView Android No support No	Chrome Android Full support 61	Firefox Android No support No	Opera Android Full support 45	Safari iOS No support No	Samsung Internet Android Full support 8.0

Legend

Full support: Full support
No support: No support
Experimental. Expect behavior to change in the future.': Experimental. Expect behavior to change in the future.

USBDevice.clearHalt() by Mozilla Contributors is licensed under CC-BY-SA 2.5.