Advanced Driver Options
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- Document Reference No.: FT_000073 Advanced Driver Options AN_107 Application Note AN_107 Version 2.53 Clearance No.: FTDI 63
- 10,27, 88,13,C4,09, E2,04,71,02, 38,41,9C,80, 4E,C0,34,00
Copyright © 2008-2014 Future Technology Devices International Limited 15
Document Reference No.: FT_000073 Advanced Driver Options AN_107 Application Note
Clearance No.: FTDI# 63 5.5 USB Timeout The USB timeout is the maximum time in milliseconds that a USB request can remain outstanding. It is unlikely that this will ever need to be changed from the 5000ms default value. This USB timeout (in milliseconds) is configurable through the FTDIBUS INF file in the INF fragments shown below: [FtdiBus.NT.HW] AddReg=FtdiBus.NT.HW.AddReg [FtdiBus.NTamd64.HW] AddReg=FtdiBus.NT.HW.AddReg [FtdiBus.NT.HW.AddReg] HKR,,"USBTimeout",0x00010001,5000 which corresponds to the registry entry HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\USB\{Device VID, PID and interface}\{Serial number}\DeviceParameters\USBTimeout The default value for the USB Timeout is 5 seconds (5000ms).
Disable EEPROM Writes In some cases, it may be desirable to disable the ability to write to the device EEPROM. This can be accomplished through a ConfigData bit in the FTDIBUS INF file. The driver can be made to ignore any EEPROM write requests by setting bit 0 of the ConfigData field as shown in the INF fragment below: [FtdiBus.NT.HW] AddReg=FtdiBus.NT.HW.AddReg [FtdiBus.NTamd64.HW] AddReg=FtdiBus.NT.HW.AddReg [FtdiBus.NT.HW.AddReg] HKR,,"ConfigData",0x00010001,1 which corresponds to the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\USB\{Device VID, PID and interface}\{Serial number}\DeviceParameters\ConfigData
The CDM driver supports USB Selective Suspend, a feature that allows the system to suspend devices that are not in use and thus reduce overall power consumption. USB Selective Suspend is controlled through bit 5 of the ConfigData parameter and the SSIdleTimeout value (in milliseconds) in the FTDIBUS.INF file. For a standard installation, the following sections can be added to FTDIBUS.INF to enable Selective Suspend: [FtdiBus.NT.HW] AddReg=FtdiBus.NT.HW.AddReg [FtdiBus.NTamd64.HW] AddReg=FtdiBus.NT.HW.AddReg [FtdiBus.NT.HW.AddReg]
Copyright © 2008-2014 Future Technology Devices International Limited 16
Document Reference No.: FT_000073 Advanced Driver Options AN_107 Application Note
Clearance No.: FTDI# 63 HKR,,"ConfigData",0x00010001,0x20 HKR,,"SSIdleTimeout",0x00010001,10000
This INF file fragment shows Selective Suspend enabled, and the Idle Timeout value set to 10 seconds. These values are held in the registry under this key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\FTDIBUS\{Device VID, PID and serial number}\0000\Device Parameters NOTE: If setting selective suspend for the driver bus layer it must not be set in the port layer (see section 6.9)
Copyright © 2008-2014 Future Technology Devices International Limited 17
Document Reference No.: FT_000073 Advanced Driver Options AN_107 Application Note
Clearance No.: FTDI# 63 6 FTDIPORT.INF Options There are many configuration options available through FTDIPORT.INF. This section describes these options and how to configure them.
Aliasing Baud Rates FTDI devices can support non-standard Baud rates. It is not necessary to alias Baud rates to achieve this, but in cases where the application software tries to set a standard Baud rate and a non-standard Baud rate is desired, this can be achieved by aliasing non-standard baud rates. Baud rates are calculated using a Baud rate divisor. The file FTDIPORT.INF contains entries that are used as the divisors for standard baud rates. By changing these values it is possible to alias standard baud rates with non-standard values - for instance replacing 115k Baud with 512k Baud. Users would then set up the device to operate at 512k Baud by selecting 115k Baud for the USB serial port. The procedure for calculating Baud rate divisors is described fully in application note AN232B-05 Configuring FT232R, FT2232 and FT232B Baud Rates . The FT8U232AM device supports sub-integer divisors of 0, 0.5, 0.25 and 0.125 only. These values can be configured through a Baud rate divisor table with two elements to define a Baud rate. The extract below from FTDIPORT.INF gives an example of the Baud rate table for standard Baud rates for the FT8U232AM device. Note that the Baud rate table is one line in the INF. [FtdiPort.NT.HW.AddReg] HKR,,"ConfigData",1,01,00,3F,3F,10,27,88,13,C4,09,E2,04,71,02,38,41,9C,80,4E,C0,34,00, 1A,00,0D,00,06,40,03,80,00,00,D0,80 In the case of the FT232R, FT2232 and FT232B devices, sub-integer divisors of 0, 0.5, 0.25, 0.125, 0.375, 0.625, 0.75 and 0.875 are supported. This requires that the Baud rate table be extended to four elements per Baud rate as indicated below. This example extract shows the four- element Baud rate table for standard Baud rates. As with the original divisors, note that the Baud rate table is one line in the INF. [FtdiPort.NT.HW.AddReg] HKR,,"ConfigData",1,11,00,3F,3F,10,27,00,00,88,13,00,00,C4,09,00,00,E2,04,00,00,71,02,
,00,03,80,00,00,00,00,00,00,D0,80,00,00 The Baud rate table used by each device is located in the registry under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\FTDIBUS\{Device VID, PID and serial number}\0000\Device Parameters\ConfigData Please note that the four-element table will not allow the use of the additional sub-integer divisors with FT8U232AM devices. The two-element table will work with all devices. For a full explanation of calculating non-standard Baud rate divisors and how to arrange them in the Baud rate table, see application note AN232B-05 Configuring FT232R, FT2232 and FT232B Baud Rates .
6.2 Changing the Default USB Transfer Size 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) [FtdiPort.NT.HW.AddReg]
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