Ithini ingqikelelo yojongano lweRS485 kuqala?
Ngamafutshane, ngumgangatho weempawu zombane, ezichazwe yi-Telecommunications Industry Association kunye ne-Electronic Industries Alliance. Uthungelwano lonxibelelwano lwedijithali olusebenzisa lo mgangatho lunokusasaza ngempumelelo imiqondiso kumgama omde nakwiindawo ezinengxolo ephezulu ye-elektroniki. I-RS-485 yenza kube nokwenzeka ukuqwalasela uthungelwano lwasekhaya olunexabiso eliphantsi kunye namakhonkco onxibelelwano amasebe amaninzi.
I-RS485 ineentlobo ezimbini zocingo: inkqubo yocingo ezimbini kunye nenkqubo yocingo ezine. Inkqubo yocingo emine inokufezekisa kuphela unxibelelwano lwe-point-to-point kwaye ayifane isetyenziswe ngoku. Okwangoku, indlela yokufaka iintambo ezimbini isetyenziswa kakhulu.
Kubunjineli bangoku obubuthathaka, unxibelelwano lwe-RS485 lusebenzisa indlela yonxibelelwano yenkosi-khoboka, oko kukuthi, umamkeli omnye onamakhoboka amaninzi.
Ukuba unokuqonda okunzulu nge-RS485, uya kufumanisa ukuba ngokwenene luninzi ulwazi ngaphakathi. Ke ngoko, siya kukhetha imiba ethile esihlala siyiqwalasela kumbane obuthathaka ukuze wonke umntu afunde kwaye ayiqonde.
I-RS-485 yeMithetho yoMbane
Ngenxa yophuhliso lwe-RS-485 ukusuka kwi-RS-422, imimiselo emininzi yombane ye-RS-485 ifana ne-RS-422. Ukuba usulelo olulungeleleneyo lwamkelwa, izichasi zokuphelisa kufuneka ziqhagamshelwe kumgca wothumelo. I-RS-485 inokusebenzisa iindlela ezimbini zocingo kunye neendlela ezine zocingo, kwaye inkqubo yocingo ezimbini inokufezekisa unxibelelwano oluyinyani lwe-multi-point bidirectional, njengoko kubonisiwe kuMfanekiso 6.
Xa usebenzisa uxhulumaniso lweengcingo ezine, njenge-RS-422, inokufikelela kuphela kwi-point-to-point yonxibelelwano, oko kukuthi, kunokubakho isixhobo esinye kuphela kunye nezinye izixhobo zekhoboka. Nangona kunjalo, inokuphucula xa kuthelekiswa ne-RS-422, kwaye inokudibanisa izixhobo ezingaphezulu ze-32 kwibhasi kungakhathaliseki ukuba yiyiphi intambo emine okanye indlela yokudibanisa iingcingo ezimbini.
I-RS-485 ye-voltage yemowudi eqhelekileyo iphuma phakathi -7V kunye + 12V, kunye ne-impedance encinci ye-receiver ye-RS-485 ye-receiver yi-12k;, Umqhubi we-RS-485 unokufakwa kwi-RS-422 networks. I-RS-485, njenge-RS-422, inomgama ophezulu wokuhambisa malunga ne-1219 yeemitha kunye nesantya esiphezulu se-10Mb / s. Ubude besibini esijijekileyo esilungeleleneyo sichasana ngokungafaniyo nesantya sothumelo, kwaye ubude obuchaziweyo bekhebula eliphezulu bunokusetyenziswa kuphela xa isantya singaphantsi kwe-100kb / s. Elona qondo liphezulu losulelo linokuphunyezwa kumgama omfutshane kakhulu. Ngokuqhelekileyo, umlinganiselo ophezulu wothumelo we-100 yeemitha ubude obujijekileyo iperi i-1Mb/s kuphela. I-RS-485 idinga i-resistors ezimbini zokuphelisa ngexabiso lokumelana elilingana ne-impedance yeempawu zentambo yokudlulisa. Xa uhambisa kumgama wexande, akukho mfuneko yokuphelisa i-resistor, ngokuqhelekileyo ayifuni ngaphantsi kweemitha ezingama-300. I-resistor yokuphelisa idibaniswe kuzo zombini iziphelo zebhasi yothumelo.
Amanqaku aphambili okufakwa kwenethiwekhi ye-RS-422 kunye ne-RS-485
I-RS-422 inokuxhasa ii-nodes ezili-10, ngelixa i-RS-485 ixhasa ii-nodes ze-32, ngoko ke iinqununu ezininzi zenza inethiwekhi. I-topology yothungelwano ngokubanzi ithatha i-terminal ehambelana nesakhiwo sebhasi kwaye ayixhasi i-ring or star network. Xa usakha inethiwekhi, kufuneka kuqatshelwe la manqaku alandelayo:
1. Sebenzisa intambo ephothiweyo njengebhasi kwaye uqhagamshele i-node nganye kuthotho. Ubude bomgca ophumayo ukusuka kwibhasi ukuya kwi-node nganye kufuneka ibe mfutshane ngokusemandleni ukunciphisa impembelelo yomqondiso obonakalisiweyo kumgca ophumayo kwi-signal yebhasi.
2. Ingqalelo iya kuhlawulwa ngokuqhubekeka kwe-impedance yeempawu zebhasi, kwaye ukubonakalisa umqondiso kuya kwenzeka kwi-Classification of discontinuities of impedance. Ezi meko zilandelayo zinokukhokelela ngokulula koku kuyeka: amacandelo ahlukeneyo ebhasi asebenzisa iintambo ezahlukeneyo, okanye zininzi kakhulu ii-transceivers ezifakelwe ngokusondeleyo kunye kwicandelo elithile lebhasi, okanye imigca yesebe emide kakhulu ikhokelela ebhasini.
Ngamafutshane, umjelo omnye, oqhubekayo wesignali kufuneka unikezwe njengebhasi.
Indlela yokuqwalasela ubude bentambo yokuhambisa xa usebenzisa i-interface ye-RS485?
Impendulo: Xa usebenzisa i-interface ye-RS485, ubude obude bekhebula obuvunyelwe ukuhanjiswa kwesignali yedatha ukusuka kwijeneretha ukuya kumthwalo kumgca othile wokuhanjiswa ngumsebenzi wezinga lesignali yedatha, eyona nto inqunyelwe ngokuchithwa kwesignali kunye nengxolo. Ijika lobudlelwane phakathi kobude obuninzi bekhebula kunye nesantya somqondiso oboniswe kulo mzobo ulandelayo ufunyenwe kusetyenziswa i-24AWG yobhedu ephothiweyo intambo yomnxeba (ene-wire diameter ye-0.51mm), kunye ne-line to line bypass capacitance ye-52.5PF / M, kunye nokumelana nomthwalo we-terminal we-100 ohms.
Xa isantya somqondiso wedatha sincipha ukuya ngaphantsi kwe-90Kbit / S, ucinga ukuba ukulahlekelwa kwesignali evumelekileyo ephezulu ye-6dBV, ubude bekhebula bukhawulelwe kwi-1200M. Enyanisweni, i-curve emfanekisweni ilondoloza kakhulu, kwaye ekusebenziseni okusebenzayo, kunokwenzeka ukufezekisa ubude bentambo enkulu kunayo.
Xa usebenzisa iintambo ezineemitha ezahlukeneyo zocingo. Ubuninzi bekhebula ubude obufunyenweyo buhluke. Ngokomzekelo, xa isantya sesignali yedatha yi-600Kbit / S kunye nekhebula le-24AWG lisetyenzisiweyo, kunokubonwa kumfanekiso ukuba ubude bekhebula eliphezulu bungama-200m. Ukuba ikhebula le-19AWG (elinocingo oluyi-0.91mm) lisetyenzisiwe, ubude bekhebula bunokuba lukhulu kune-200m; Ukuba i-cable ye-28AWG (ene-wire diameter ye-0.32mm) isetyenzisiwe, ubude bentambo bunokuba ngaphantsi kwe-200m kuphela.
Indlela yokufezekisa unxibelelwano lwamanqaku amaninzi e-RS-485?
Impendulo: Inye kuphela isidluliseli esinokuthumela ngebhasi yeRS-485 nangaliphi na ixesha. Isiqingatha se-duplex mode, kunye nekhoboka elinye kuphela. Imowudi ye-duplex epheleleyo, isikhululo esikhulu sinokuhlala sithumela, kwaye isikhululo samakhoboka sinokuthumela enye kuphela. (Ilawulwa ngu kunye ne DE)
Kuphantsi kwaziphi iimeko apho ukuhambelana kwetheminali kufuneka kusetyenziswe kunxibelelwano lwe-RS-485 ujongano? Indlela yokumisela ixabiso lokumelana? Indlela yokuqwalasela izichasi ezihambelana netheminali?
Impendulo: Ekuhanjisweni kwesignali yomgama omde, ngokuqhelekileyo kuyimfuneko ukudibanisa i-terminal ehambelana ne-resistor ekupheleni kokufumana ukuphepha ukubonakalisa umqondiso kunye ne-echo. Ixabiso le-terminal elihambelana nokumelana lixhomekeke kwiimpawu ze-impedance zentambo kwaye zizimeleyo kubude bekhebula.
I-RS-485 ngokubanzi isebenzisa iperi ejijekileyo (ekhuselweyo okanye engakhuselekanga) udibaniso, kunye noxhathiso lwesiphelo phakathi kwe-100 kunye ne-140 Ω, ngexabiso eliqhelekileyo le-120 Ω. Ekubunjweni kwangempela, i-resistor enye ye-terminal ixhunyiwe kwi-terminal nodes ezimbini ze-cable, i-node esondeleyo kunye nekude kakhulu, ngelixa i-node ephakathi ayinakuxhunywa kwi-resistor ye-terminal, ngaphandle koko iimpazamo zonxibelelwano ziya kwenzeka.
Kutheni i-RS-485 i-interface isenayo imveliso yedatha evela kumamkeli xa unxibelelwano lumisiwe?
Impendulo: Ekubeni i-RS-485 idinga ukuba yonke i-transmission yenza ukuba iimpawu zokulawula zicinywe kwaye ukwamkelwa kuvumeleke ukuba kusebenze emva kokuthumela idatha, umqhubi webhasi ungena kwindawo ephezulu yokuchasana kwaye ummkeli unokubeka iliso ukuba kukho idatha yonxibelelwano entsha kwibhasi.
Ngeli xesha, ibhasi ikwimo yokuqhuba (ukuba ibhasi inesithintelo esihambelana netheminali, inqanaba lokwahluka kwemigca A kunye no-B ngu-0, isiphumo somamkeli asiqinisekanga, kwaye inovakalelo kutshintsho lomqondiso umahluko umgca AB; ukuba akukho theminali ehambelanayo, ibhasi ikwimeko ephezulu ye-impedance, kwaye imveliso yomamkeli ayiqinisekanga), ngoko isengozini yokuphazamiseka kwengxolo yangaphandle. Xa i-voltage yengxolo idlula umda wesignali yegalelo (ixabiso eliqhelekileyo ± 200mV), umamkeli uya kukhupha idatha, ebangela ukuba i-UART ehambelanayo ifumane idatha engavumelekanga, ebangela iimpazamo zonxibelelwano eziqhelekileyo ezilandelayo; Enye imeko inokuthi yenzeke ngexesha apho unikezelo luvumela ulawulo luvuliwe/luvaliwe, nto leyo ebangela ukuba umamkeli akhuphe umqondiso, nto leyo enokubangela ukuba i-UART ifumane ngokungalunganga. Isisombululo:
1) Kwibhasi yonxibelelwano, indlela yokutsalela phezulu (umgca A) kwisiphelo segalelo lesigaba esifanayo kunye nokutsalela ezantsi (umgca B) kwisiphelo senqanaba elichaseneyo lisetyenziselwa ukucinezela ibhasi, ukuqinisekisa ukuba isiphumo somamkeli sikwindawo inqanaba "1" elimisiweyo; 2) Faka indawo yesekethe ye-interface kunye ne-MAX308x yeemveliso ze-series interface kunye nemodi yokukhusela impazamo eyakhelwe-ngaphakathi; I-3) Ukuphelisa ngeendlela zesoftware, oko kukuthi, ukongeza i-2-5 bytes yongqamaniso yokuqala ngaphakathi kwepakethi yedatha yonxibelelwano, kuphela emva kokuba i-header yokuvumelanisa idibene inokuqala unxibelelwano lwedatha yangempela.
Ukunciphisa umqondiso we-RS-485 kwiintambo zonxibelelwano
Into yesibini echaphazela ukuhanjiswa kwesignali kukuthotywa kwesiginali ngexesha lokuhanjiswa kwekhebula. Ikhebula lokuhambisa linokubonwa njengesekethe elinganayo ehlanganiswe ngokudibanisa i-capacitance esasazwayo, i-inductance eyabiwayo, kunye nokuchasana.
I-capacitance ye-C esasazwayo yekhebula iveliswa ikakhulu ngeengcingo ezimbini ezihambelanayo zesibini esijijekileyo. Ukuchasana kocingo kunempembelelo encinci kwi-signal apha kwaye inokungahoywa.
Impembelelo yeSakhono esiSasazo kuMsebenzi woThutho lwebhasi yeRS-485
I-capacitance esasazwayo yekhebula iveliswa ikakhulu ngeengcingo ezimbini ezihambelanayo zesibini esijijekileyo. Ukongezelela, kukho kwakhona i-capacitance eyabiwayo phakathi kocingo kunye nomhlaba, leyo, nangona incinci kakhulu, ayinakuhoywa kuhlalutyo. Impembelelo ye-capacitance esasazwayo ekusebenzeni kokuhanjiswa kwebhasi ikakhulu ngenxa yokuhanjiswa kweempawu ezisisiseko kwibhasi, ezinokubonakaliswa kuphela kwiindlela "ze-1" kunye ne "0". Kwi-byte ekhethekileyo, njenge-0x01, isignali "0" ivumela ixesha elaneleyo lokutshaja kwi-capacitor esasazwayo. Nangona kunjalo, xa umqondiso "1" ufika, ngenxa yentlawulo kwi-capacitor esasazwayo, akukho xesha lokukhupha, kwaye (Vin +) - (Vin -) - isenkulu kune-200mV. Oku kubangela ukuba umamkeli akholelwe ngempazamo ukuba ngu-"0", ekugqibeleni kukhokelele kwiimpazamo zoqinisekiso lwe-CRC kunye nayo yonke impazamo yokuhanjiswa kwesakhelo sedatha.
Ngenxa yempembelelo yokusasazwa kwibhasi, iimpazamo zokuhanjiswa kwedatha zenzeka, okukhokelela ekunciphiseni komsebenzi womnatha jikelele. Kukho iindlela ezimbini zokusombulula le ngxaki:
(1) Ukunciphisa i-Baud yokuhanjiswa kwedatha;
(2) Sebenzisa iintambo ezinamacapacitor amancinci asasazwayo ukuphucula umgangatho wemigca yokuhambisa.
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Ixesha lokuposa: Jul-06-2023