UnicodeECN

USBEngineeringChangeNoticeUSBECN:UNICODEUTF-16LEforStringDescriptorsFebruary21,2005Title:UNICODEUTF-16LEforStringDescriptorsAppliesto:UniversalSerialBusSpecification,Revision2.0SummaryofECNThisECNmorecompletelyspecifiestheencodingschemeforstringdescriptors.StringdescriptorsmustuseUNICODEUTF-16LEencodings.ReasonsforECNToensureconsistentcodinganddecodingofstringdescriptors,thespechastobeclearontheexactencodingtouse.TheoriginalspecsaidtouseUNICODEencodings,buttherearemultipleencodingschemesthatmakeupUNICODE.UTF-16LEwastheintendedencodingscheme,andtheoneassumedbymostdevelopers.ImpactonExistingPeripheralsandSystemsUSBcompliancetestingchecksforproperencodingofstringdescriptorsonperipherals.TherearenoknowncasesofdevicesusinganencodingotherthanUTF-16LE.ThereisatleastoneOSthathasbeenusingUTF-8encodingandignoringnullbytes.SincemostdeviceshavebeenencodingASCIIcharactersresultingintheupperbytebeingNULL,thishasnotbeenaproblem.HardwareImplicationsNoneexpected.SoftwareImplicationsAnysoftwarenotusingUTF-16LEwillneedtochange.ComplianceTestingImplicationsNone.USBcompliancetestingalreadychecksstringdescriptorsforproperUTF-16LEencoding.USBEngineeringChangeNoticeUSBECN:UNICODEUTF-16LEforStringDescriptorsSpecificationChangesSection9.6.7String,p.273ChangeThis:…StringdescriptorsuseUNICODEencodingsasdefinedbyTheUnicodeStandard,WorldwideCharacterEncoding,Version3.0,TheUnicodeConsortium,Addison-WesleyPublishingCompany,Reading,Massachusetts(URL:).…Tothis:…StringdescriptorsuseUNICODEUTF-16LEencodingsasdefinedbyTheUnicodeStandard,WorldwideCharacterEncoding,Version4.0,TheUnicodeConsortium,Addison-WesleyPublishingCompany,Reading,Massachusetts(URL:).…Table9-16,p.274ChangeDescriptionofbStringfromthis:UNICODEencodedstringTothis:UNICODEUTF-16LEencodedstring