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This function takes an already initialized USB device list, searches for Trenz Electronic USB FX2 devices (Cypress driver derivative and VID = 0xbd0, PID=0x0300) connected to host computer's USB ports and counts them.
An internal operation that closes an handle to the CyUSB.sys driver (or a derivative like TE_USB_FX2_xx.sys) is executed instead (see page 33 of CyAPI.pdf).
If one or more devices are attached and

  • if 0 ≤ CardNumber ≤ (number of attached devices – 1), thenthe selected module is not directly given by USBDeviceList (CCyUSBDevice type). An internal operation that opens a handle to CyUSB.sys driver (or a derivative like TE driver) is executed instead (see page 45 of CyAPI.pdf). This handle is internally managed by CyAPI.lib, therefore there is no need to expose them to the user.
  • if CardNumber ≥ number of attached devices, thenUSBDeviceList (CyUSBDevice type) is not initialized to null (the device list is not erased). An internal operation that closes an handle to CyUSB.sys driver (or a derivative like TE driver) is executed instead (see page 33 of CyAPI.pdf).
Info
A more intuitive name for this function would have been TE_USB_FX2_SelectCard().
Note
You can use this function to select the desired module without the need to call TE_USB_FX2_Close() before. Though doing so would not cause any problems.
Close() is automatically carried out by the TE_USB_FX2_Open() function if a handle to the driver is already open (i.e. a TE_USB_FX2_Open() has been successfully called before).
Note

If no device is attached, USBDeviceList is not initialized to null (the device list is not erased).

Description of internal procedure

TE_USB_FX2_SetData_InstanceDriverBuffer() function instantiates the class used by CyAPI to use Bulk EndPoint (CCyBulkEndPoint, see pages 9 to 11) and initializes the parameters of this class instantiation.

The parameters are :

  1. Timeout
  2. XMODE_DIRECT (this parameter set the driver to single buffering, instead the slower double buffering)
  3. DeviceDriverBufferSize.

The last parameter force the instantiation of the driver buffer (SW side, on the host computer) for the endpoint 0x86; this buffer has a size in byte given by DeviceDriverBufferSize. This value is of great importance because the data throughput is strongly influenced by this parameter (see Data Transfer Throughput Optimization).

Use of the code

Declaration

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