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USBDevice: clearHalt() method

Experimental: 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 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

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

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
clearHalt 61 79 No No 48 No No 61 No 45 No 8.0

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https://developer.mozilla.org/en-US/docs/Web/API/USBDevice/clearHalt