Iphini lokufaka le-Arduino elingaxhunyiwe lifunda i-HIGH—noma lincwazimula ngokungalindelekile phakathi kwe-HIGH ne-LOW—ngoba lisesimweni se-high-impedance esaziwa ngokuthi i-floating pin (iphini elintantayo). Alixhunyiwe ku-voltage eyisithenjwa, okusho ukuthi lisebenza njenge-antena encane, eqoqa amandla kazibuthe kagesi aseduze (electromagnetic fields), ugesi omile (static electricity) ovela ezandleni zakho, kanye nomsindo we-50 Hz wezintambo zikagesi eziseduze.

Ukuze uthole ukufundeka okuzinzile nokulindelekile, iphini ngalinye lokufaka le-digital kufanele liboshwe ngendlela ehlanzekile ku-voltage ephozithivu (HIGH) noma ku-ground (LOW) ngazo zonke izikhathi. Awudingi ukushisela ama-resistor angaphandle noma ugcwalise i-breadboard yomfundi ukuze ufeze lokhu: cishe wonke ama-microcontroller anamuhla ahlanganisa ama-pull-up resistor angaphakathi angacushwa ngomugqa owodwa nje wekhodi.

Inkinga Ye-High-Impedance

Lapho ulungiselela iphini usebenzisa i-pinMode(pin, INPUT), i-microcontroller ibeka umjikelezo wangaphakathi walelo phini esimweni se-high-impedance. Ku-ATmega328P (i-microcontroller esebenza kumabhodi e-Arduino Uno ne-Nano ajwayelekile), i-resistance yokufaka yephini elijwayelekile le-GPIO icishe ibe ngama-megaohm ayi-100 (100,000,000 Ω). Iphini alidonsi cishe amandla kagesi (current)—lingaphansi kwe-microampere eyodwa.

Lokhu kwenziwa ngamabomu: kuvumela i-microcontroller ukuba ikale umjikelezo wangaphandle ngaphandle kokwengeza umthwalo kuwo noma ukuphazamisa isiginali. Kodwa-ke, lokho kuzwela kunomphumela oqondile ongokomzimba. Ngenxa yokuthi cishe akudingeki amandla kagesi ukushintsha i-voltage yesango (gate voltage) ngaphakathi kwe-chip, izindleko ezincane kakhulu ze-electrostatic ebusweni bephini noma intambo emfushane ye-jumper zanele ukukhuphula i-voltage yephini ngaphezu komkhawulo we-digital.

Ebhodini elingu-5V, noma yini engaphezu kwelinganiselwa ku-3.0V ibhaliswa njenge-HIGH, kanti noma yini engaphansi kwelinganiselwa ku-1.5V ibhaliswa njenge-LOW. Lapho iphini lingaxhunyiwe kulutho, i-voltage yalo izulazula ngaphandle kwenhloso kuleyo ndawo ephakathi nendawo. Ngesikhathi uphakamisa isandla, ushubeza izinyawo zakho kukhaphethi wokwenziwa wasekilasini, noma uletha ishaja ye-laptop eduze, ukuxhumana kwe-capacitive (capacitive coupling) kuphusha i-voltage ngaphezu komkhawulo, bese i-digitalRead() ibuyisa u-1 (HIGH).

Isimo Esijwayelekile Sokwehluleka Ekilasini

Emakilasini ezikole nasemaklabhini e-robotics, lesi simo sidala izinkinga zokulungisa amaphutha (debugging) ezilindelekile:

• Ukucindezelwa kwenkinobho okungacacile (phantom button presses): Umfundi ubhala ikhodi yokukhanyisa i-LED lapho kucindezelwa inkinobho. Ngesikhathi efaka i-sketch, i-LED iyakhanya ngokushesha, nakuba inkinobho ingakathintwa.
• Umphumela wokuntanta (the hover effect): Inzwa ye-robot (sensor) ivuka ngenxa yokuthi isandla somfundi sisondele ngaphakathi kwamasentimitha ayishumi ukusuka ebhodini, okwenza ikilasi licabange ukuthi intambo yalo ye-jumper isiphenduke inzwa yokusondela engahlosiwe.
• Ukungazinzi kokuziphatha kwe-breadboard: Iphrojekthi isebenza ngokuthembekile edeskini likathisha, kodwa yenze ngendlela engafanele lapho ibekwa edeskini lesikole elinohlaka lwensimbi ngaphansi kwezibani ze-fluorescent.

Ikhambi elijwayelekile lencwadi ukufaka i-pull-down noma i-pull-up resistor yangaphandle engu-10kΩ ku-breadboard. Nokho, ekilasini labaqalayo, ama-resistor angaphandle adala ubunzima obungadingekile: abafundi bawaxhuma kumzila ongewona, baphambanise amabhande emibala, noma badale ama-short circuit phakathi kuka-5V no-GND lapho becindezela izinkinobho zokucindezela.

Isixazululo Esihlanzekile: INPUT_PULLUP

Abakhi be-microcontroller babona le nkinga kusengaphambili emashumini eminyaka edlule. Ama-microcontroller afana ne-ATmega328P, i-RP2040, kanye ne-ESP32 aqukethe ama-resistor angaphakathi akhelwe ngqo ku-silicon eduze kwephini ngalinye le-GPIO. Ku-Arduino Uno noma Nano, lawa ma-resistor angaphakathi ane-resistance esebenzayo ephakathi kuka-20kΩ no-50kΩ.

Ungawasebenzisa lawa ma-resistor ngokuqondile ngaphakathi komsebenzi wakho we-setup() ngokufaka i-constant eyodwa ku-pinMode():

void setup() {
  pinMode(2, INPUT_PULLUP);
  pinMode(LED_BUILTIN, OUTPUT);
}

Lapho kubizwa i-INPUT_PULLUP, i-microcontroller ixhuma iphini 2 ngaphakathi kugesi walo wangaphakathi ongu-5V kusetshenziswa i-resistor engu-20kΩ–50kΩ. Lokhu kuxhumana okubuthakathaka kudonsela iphini phezulu kancane ku-5V noma nini lapho iphini lishiywe livulekile (open-circuit). Ngenxa yokuthi iphini seliboshwe ngempumelelo emthonjeni we-voltage, umsindo we-electrostatic olahlekile awusakwazi ukushintsha isimo salo. Uma lingathintwanga, iphini lizofunda i-HIGH ngokuthembekile nangokuzinzile.

Ukushintsha Komqondo: Ukuhlanganisa Izintambo Ze-Active-LOW

Ukusebenzisa i-INPUT_PULLUP kudinga ushintsho oluncane lokucabanga kubafundi: umjikelezo wakho kufanele usebenzise umqondo we-active-LOW.

Ngenxa yokuthi iphini lidonselwa ku-HIGH ngokuzenzakalelayo, inkinobho yokucindezela akufanele ixhume iphini ku-5V. Esikhundleni salokho, inkinobho kufanele ixhume iphini ngqo ku-GND:

• Inkinobho ingacindezelwe (umjikelezo uvulekile): I-pull-up yangaphakathi igcina iphini liku-5V. I-digitalRead(pin) ibuyisa i-HIGH.
• Inkinobho icindezelwe (umjikelezo uvaliwe): Iphini liboshwe ngqo ku-Ground (0V). Amandla kagesi amancane adlula ku-resistor ye-pull-up yangaphakathi aphumela ngokuphepha ku-GND. I-digitalRead(pin) ibuyisa i-LOW.

Ukuxhuma izingxenyekazi zekhompyutha (hardware) kuba lula: udinga izintambo ezimbili kuphela zokushintsha kwakho—eyodwa eya ephini le-digital, kanti enye eya kunoma yiliphi iphini le-ground (GND) ebhodini. Ususa ngokuphelele ukuxhumana komzila ongu-5V kanye nama-resistor angaphandle.

Kusoftware, uvele uhlehlise isimo:

void loop() {
  int buttonState = digitalRead(2);

  // Nge-INPUT_PULLUP, i-LOW isho ukuthi inkinobho icindezelwe
  if (buttonState == LOW) {
    digitalWrite(LED_BUILTIN, HIGH);
  } else {
    digitalWrite(LED_BUILTIN, LOW);
  }
}

Isikhathi Sokusebenzisa Ama-Resistor Angaphandle Esikhundleni Salokho

Ngenkathi i-INPUT_PULLUP kufanele ibe yindlela evamile yokushintsha kwe-digital ekilasini, inemikhawulo esekelwe kwifisiksi eyisisekelo:

Kwezingxenyekazi zekhompyutha ezihleleke ngamamojula ze-STEM nezinkundla zokuhlola ezisekilasini lapho amaphutha okufaka izintambo edinga ukuncishiswa, hlola izingxenye ze-microcontroller ezikhethiwe nezinzwa ezitholakala nge-Sheen Robotics Store.

Uhla Lokuhlola Lwesifinyezo LwabaFundisi

1. Ungalokothi ushiye okokufaka kuntanta: Uma iphini lokufaka lilungiselelwe nge-INPUT evamile, kufanele liboshwe ngokuqhubekayo ku-voltage ecacisiwe ngomjikelezo wangaphandle.
2. Qalisa nge-INPUT_PULLUP njengokujwayelekile: Shintsha izifanekiso zakho zezifundo ezijwayelekile ukuze uqale amaphini nge-pinMode(pin, INPUT_PULLUP).
3. Xhuma izinkinobho ku-GND, hhayi ku-5V: Lokhu kunciphisa inani lezingxenye ku-breadboard, kususa ubungozi bama-short-circuit, futhi kulingisa izinqubo ezijwayelekile zokufaka izintambo zezimboni.
4. Fundisa i-active-LOW kusenesikhathi: Ukuchaza ukuthi kungani i-LOW isho ukuthi "kuvuliwe" kwethula abafundi kwingqondo kagesi yomhlaba wangempela, lapho ukuxhuma umjikelezo osebenzayo ku-ground kuphephe kakhudlwana futhi kuqine kakhulu kunokuhambisa imizila ephozithivu ezinkinobheni zangaphandle.