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
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.
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
Specification |
---|
WebUSB API # ref-for-dom-usbdevice-clearhalt① |
Browser compatibility
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