USBDevice.clearHalt()

This is an experimental technology
Check 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
WebUSB
The definition of 'clearHalt()' in that specification.
Draft Initial definition.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic support
Experimental
Chrome Full support 61Edge No support NoFirefox No support NoIE No support NoOpera Full support 48Safari No support NoWebView Android No support NoChrome Android Full support 61Edge Mobile No support NoFirefox Android No support NoOpera Android Full support 48Safari iOS No support NoSamsung Internet Android No support No

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.

Document Tags and Contributors

Contributors to this page: jpmedley
Last updated by: jpmedley,