PICO USB TC-08 - New USB Mode and Legacy Mode; Usb_Tc08_Open_Unit

Technical reference
16
© 2005 Pico Technology Limited. All rights reserved.
USBTC08044-2
3.3.2
New USB mode and legacy mode
3.3.2.1
usb_tc08_open_unit
short usb_tc08_open_unit (void)
This routine returns a valid handle to the USB TC-08 if the driver successfully opens it. If
the routine fais, see the error code explanations in the
usb_tc08_get_last_error
section.
If
you wish to use more than one USB TC-08, call this routine once for each unit connected
to the PC. The function will return 0 if there are no more units found. The driver is thread-
safe and will not allow access to a single unit from more than one application. If,
therefore,
usb_tc08_open_unit
does not find a unit, check that other applications are
not using the USB TC-08. This includes applications on other user accounts on the same
computer, where fast user switching is supported.
Note: The
usb_tc08_open_unit
function provides a simple way to open USB TC-08
units. However, the function call locks up the calling thread until the attached USB TC-08
unit has been fully enumerated. If a single-threaded application needs to perform
concurrent processing, such as displaying a progress bar, use
usb_tc08_open_unit_async
.
Arguments:
None
Returns:
Positive short
- The handle to a unit.
0
- No more units were found.
-1
- Unit failed to open. Call
usb_tc08_get_last_error
with a handle of
0 to obtain the error code.
Example
The following code is a fragment of a C application which demonstrates how to open
multiple units with the USB TC-08 driver. The handles to the open units are stored in an
array for later use:
//======================================================
// Opening multiple units
//======================================================
for
(i =
0
; (new_handle =
usb_tc08_open_unit
()) >
0
; i++)
{
// store the handle in an array
handle_array[i] = new_handle;
}
no_of_units = i;
// deal with the error if there is one,
// if new_handle was zero, then there was no error
// and we reached the last available unit
if
(new_handle == -
1
)
{
error_code =
usb_tc08_get_last_error
(
0
);
printf(
"Unit failed to open\nThe error code is %d"
, error_code);
// could terminate the application here
}
//