FTDIBUS Options

Introduction

This document describes configuration options for FTDIBUS.SYS.  For most operating environments, the default configuration of FTDIBUS is sufficient for normal operation, and it is very unlikely that any of the parameters described here need to be altered.

ResetPipeRequestRetryCount

ResetPipeRequestRetryCount controls the maximum number of times that FTDIBUS tries to reset a pipe on which an error has occurred.  ResetPipeRequestRetryCount defaults to 50.  It may be necessary to increase this value in noisy environments where a lot of USB errors occur.

The default can be overridden via RetryResetCount in the FTDIBUS service key

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\FTDIBUS\Parameters\RetryResetCount

The device can be installed with ResetPipeRequestRetryCount set to any value by changing FTDIBUS.INF as shown in the following fragment.

[FtdiBus_AddService.AddReg]
HKR,Parameters,"RetryResetCount",0x10001,100

Here, the count is set to 100.

MaxDevices

MaxDevices is used to place a limit on the number of COM ports that can be created in a system by FTDIBUS.  MaxDevices defaults to 0, meaning that the feature is disabled and FTDIBUS always attempts to create a COM port.

The default can be overridden via MaxDevs in the FTDIBUS service key.

Note that setting MaxDevs to a value other than zero will radically alter the behaviour of the driver; please contact FTDI if you think you have to change MaxDevs.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\FTDIBUS\Parameters\MaxDevs

The device can be installed with MaxDevs set to any value by changing FTDIBUS.INF as shown in the following fragment.

[FtdiBus_AddService.AddReg]
HKR,Parameters,"MaxDevs",0x10001,3

Here, the maximum number of devices is set to 3.

Location IDs

Location IDs is used to define the set of USB ports supported by FTDIBUS.  It can be used in systems that require only certain USB ports to be available, perhaps in conjunction with MaxDevices.  The default behaviour is that all USB ports are supported.

The default can be overridden via LocIds in the FTDIBUS service key.

Note that setting LocIds will radically alter the behaviour of the driver; please contact FTDI if you think you have to change LocIds.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\FTDIBUS\Parameters\LocIds

LocIds is a binary value that is interpreted as an array of Location IDs.  A Location ID is a 32-bit unsigned integer (DWORD) that represents the location of the device in the USB tree.  For example, if the driver creates a location string for the device of the form a&b&c, the location ID will be 0x00000abc.

The device can be installed with LocIds set by changing FTDIBUS.INF as shown in the following fragment.

[FtdiBus_AddService.AddReg]
HKR,Parameters,"LocIds",1,21,00,00,00,32,00,00,00,11,00,00,00

Here, three USB ports are supported.  Location ID 0x00000021 represents host controller 1 port 1.  Location ID 0x00000032 represents host controller 2 port 2.  Location ID 0x00000011 represents host controller 0 port 1.

Location IDs can be obtained using the latest version of the utility USBView available from FTDI support.

FTDI

19 January 2004