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Given a PacketSize of 102,400 bytes (it can be subdivided into 200 USB packets of 512 bytes), the influence of XferSize (driver buffer size reserved for data communication) on the throughput is reported in the following table.

To change XferSize in C++, the method

Code Block
languagecpp
BulkEndPoint->SetXferSize(DesiredValue);

shall be used. Cypress sets DesiredValue to 4,096 bytes by default. This default value is not documented in the CyAPI.lib manual (pag 62 of CyAPI.pdf), but it has been retrieved by using the following C++ instructions:

Code Block
languagecpp
int XferSizeReadValue = BulkEndPoint->GetXferSize();
cout<< "XferSizeReadValue" << XferSizeReadValue <<endl;
Scroll Title
titledata throughput as a function of XferSize given PacketSize = 102,400 bytes

XferSize
(bytes)

Throughput
(Mbyte/s)

Data throughput [Mbyte/s] as a function of XferSize [byte]
given PacketSize = 102,400 bytes.

PacketSize = 102,400
(bytes)

4,096 (1)

15.64

8,192

20.4

16,384

26.37

32,768

30.24

65,536

34.12

131,072

36.25

262,144

36.78


(1) Cypress XferSize Default = 4096

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