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

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support61 No No No48 No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support No61 No No48 No No

Document Tags and Contributors

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