Specifications

EssentialsofCrestronProgramming
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90
User Modules
CrestronprocessorscontrolserialdevicesusingphysicalstandardssuchasRS‐232,RS‐
422,andRS‐485.UnlikeIR,RS‐232controldoesnotuseready‐to‐godriverfiles.Instead,
theprotocolthatthedeviceisexpectingwillbeprovidedbythemanufacturerinthe
unitʹsdocumentation.Thisprotocolincl
udesthedatathatthedeviceexpectstoreceive
andtransmit,theformatoftheserialcommands,thespeedatwhichitcommunicates
(baudrate),theerrorchecking(parity),andotherelementswhichallhavetobeadjusted
inamoduletomatchthemanufacturerʹsspecification.
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Becauseoftheabsenceofadriverfile,RS‐232controlisgenerallyconsideredmore
difficulttopr
ogramthanIR.ThisisbecauseeachtimeanRS‐232deviceistobe
programmed,theprogrammermustlookuptheprotocolinthemanual,andthenwrite
thenecessarylogicintotheprogramtosendth
isdata.(Tocounterthis,manydevices
havededicatedCrestronmoduleswrittenforthem.Thesemodulescanbepluggedinto
aprogramandusedtogenerateallthepropercontrolcodesautomatically.)
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TheVirtualPresentationRoomincorporatesasimplemodulethatsendsserialcommand
stringstotheprojectortoturntheprojectoronandoffandtoselectsources.Theserial
outputstrin
gofthemoduleistransmittedtotheCOMportviathe<tx$>inputofthe
builtinserialdriver,andontotheprojectorviatheserialcable.
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Elementsofausermodule
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AmoduleconsistsofanArgumentDefinition,whichrepresentshowthesymbolwill
lookinSIMPLWindows,andlogicsymbols.
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Theinputs,outputsandparametersoftheArgumentDefinitionareassociatedwith
signalsandparametersdefinedinthemodule.