USBDevice: clearHalt() method

Limited availabilitySecure contextAvailable in workers

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

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.

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