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Changing the Default USB Transfer Size
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The default USB transfer size may be set up at installation through the ConfigData entry in the FTDIPORT.INF file. This is the same entry that contains the Baud rate table.

The options can be set through the first DWORD of the table (shown in bold below)


This entry is byte-reversed, so MSB the DWORD reads 3F 3F 00 01 and the least significant bit is Bit 0. The values are given as follows:

   Bits 16 - 23:   Receive transfer size
   Bits 24 - 31:   Transmit transfer size

The maximum value permitted in each case is 3F this is the standard default value.

The transfer size in bytes may be calculated as

Transfer size in bytes = (Transfer size entry + 1) * 0x40  

The USB transfer sizes used by a device are located in the registry under

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\FTDIBUS\{Device VID, PID and serial number}\0000\Device Parameters\ConfigData