UsbControlRequest Procedure |
Version 7 |
Sends and receives control setup packet to the specified USB device.
[ lStatus = ] UsbControlRequest ( hDevice, ucBmRequestType, ucRequest, wValue, wIndex, wLength, pSendData, pReceiveData, lEndpointAddress )
The UsbControlRequest procedure syntax has the following parts:
|
Name |
Type |
Description |
|
lStatus |
Long |
Status: -1 for error, >=0 indicates # bytes sent or received |
|
hDevice |
Val AHandle |
Handle to the USB device |
|
ucBmRequestType |
Val Byte |
Characteristics of the request (i.e Direction, Type, and Recipient) |
|
ucRequest |
Val Byte |
Specific request |
|
wValue |
Val Word |
Varies according to request. typically used for data. |
|
wIndex |
Val Word |
Varies according to request; typically used to pass an index or offset. |
|
wLength |
Val Word |
Number of bytes to send or receive if there is a Data stage |
|
pSendData |
[Val] Any |
Send Data Buffer |
|
pReceiveData |
[Var] Any |
Receive Data Buffer |
|
lEndpointAddress |
[Val] Long |
Optional Endpoint address, default=0 |
Sends control request to a USB control pipe. The request and its parameters are sent to the device in the Setup packet. Please see USB 2.0 specifications section 9.3 "USB Device Request" for more details. (see http://www.usb.org/developers/devclass_docs#approved).
If the endpoint address of the control pipe is not specified, default control pipe with address 0 will be used.
The following example sends a request to retrieve the configuration descriptor of a USB device:
! aucConfigDesc : Byte[1000]
UsbControlRequest(hDevice, 0x80, 0x06, 0x0200, 0, 1000, , aucConfigDesc)