viUsbControlIn
Purpose
Performs a USB control pipe transfer from the device.
 |
Note This operation is intended only for users familiar with the USB protocol. |
C Syntax
ViStatus viUsbControlIn (ViSession vi, ViInt16 bmRequestType, ViInt16 bRequest, ViUInt16 wValue, ViUInt16 wIndex, ViUInt16 wLength, ViPBuf buf, ViPUInt16 retCnt);
Visual Basic Syntax
viUsbControlIn& (ByVal vi&, ByVal bmRequestType%, ByVal bRequest%, ByVal wValue%, ByVal wIndex%, ByVal wLength%, buf As Byte, retCnt%)
Resource Classes
USB INSTR, USB RAW
Parameters
| Name | Direction | Description |
|---|---|---|
|
vi |
IN |
Unique logical identifier to a session. |
|
bmRequestType |
IN |
The bmRequestType parameter of the setup stage of a USB control transfer. Refer to the USB specification for further details. |
|
bRequest |
IN |
The bRequest parameter of the setup stage of a USB control transfer. |
|
wValue |
IN |
The wValue parameter of the setup stage of a USB control transfer. |
|
wIndex |
IN |
The wIndex parameter of the setup stage of a USB control transfer. This is usually the index of the interface or endpoint. |
|
wLength |
IN |
The wLength parameter of the setup stage of a USB control transfer. This value also specifies the size of the data buffer to receive the data from the optional data stage of the control transfer. |
|
buf |
OUT |
The data buffer that receives the data from the optional data stage of the control transfer. This is ignored if wLength is 0. |
|
retCnt |
OUT |
Number of bytes actually transferred in the optional data stage of the control transfer. This parameter may be VI_NULL if you do not need this information. |
Return Values
| Error Codes | Description |
|---|
|
VI_ERROR_INV_OBJECT |
The given session reference is invalid. |
|
VI_ERROR_RSRC_LOCKED |
Specified operation could not be performed because the resource identified by vi has been locked for this kind of access. |
|
VI_ERROR_TMO |
Timeout expired before operation completed. |
|
VI_ERROR_INV_SETUP |
Unable to start write operation because setup is invalid (due to attributes being set to an inconsistent state). |
|
VI_ERROR_IO |
An unknown I/O error occurred during transfer. |
|
VI_ERROR_CONN_LOST |
The I/O connection for the given session has been lost. |
|
VI_ERROR_INV_PARAMETER |
The value of some parameter—which parameter is not known—is invalid. |
|
VI_ERROR_INV_MASK |
The bmRequestType parameter contains an invalid mask. |
Description
The viUsbControlIn() operation synchronously performs a USB control pipe transfer from the device. The values of the data payload in the setup stage of the control transfer are taken as parameters and include bmRequestType, bRequest, wValue, wIndex, and wLength. An optional data buffer buf receives data if a data stage is required for this transfer. Only one USB control pipe transfer operation can occur at any one time.
Related Topics