PTZ Control Deep Dive: RS485 Bus Nnyinasosɛm, Protocol, ne Ɔhaw a Wɔtaa Di Dwuma

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Ɔberɛfɛw da 18, afe 2023

RS485 yɛ differential serial communication standard a ɛde signal lines mmienu (a wɔtaa frɛ no A ne B, anaa + ne -) di dwuma de mena data. Mfaso titiriw a ɛwɔ differential signaling so ne tumi a emu yɛ den a ɛko tia interference.

RS485 Honam fam Layer: Ɛnyɛ Nhama Abien Kwan

RS485 yɛ differential serial communication standard a ɛde signal lines mmienu (wɔtaa frɛ no A ne B, anaa + ne -) di dwuma de mena data. Mfaso titiriw a ɛwɔ differential signaling so ne anti-interference tumi a emu yɛ den — receiver no hu voltage nsonsonoe a ɛda nhama abien no ntam sen sɛ obehu voltage a edi mũ a ɛfa asase ho. Eyi kyerɛ sɛ wɔtwa dede a ɛyɛ common-mode (te sɛ interference a motor ahorow a ɛbɛn anaa variable frequency drives de ba) no mu ara kwa.

Nanso mfaso a ɛwɔ differential signaling so no de ɛka bi ba. RS485 bɔs no hwehwɛ sɛ wɔde termination resistors a ɛteɛ (a ɛtaa yɛ 120 ohms) hyehyɛ bɔs no ano abien no nyinaa na ama wɔayi signal reflections afi hɔ. Sɛ termination resistor no yera anaasɛ wɔde ahyɛ beae a ɛnteɛ a, signal reflections de data mfomso ba — ɛda adi sɛ signal overshoot na ɛrebɔ wɔ oscilloscope so. Wɔ mfiridwuma a wɔde di dwuma mu no, termination resistor a ɛyera yɛ nneɛma a ɛtaa ma PTZ control di nkogu no mu biako.

Pelco-D vs Pelco-P: Protocol a Wɔpaw no Ɛnyɛ Nea Wɔpaw

PTZ control protocols a wɔtaa de di dwuma wɔ ahobammɔ sohwɛ mu ne Pelco-D ne Pelco-P. Nnipa mmienu no nyinaa yɛ serial communication protocols, nanso ɛsono data formats: Pelco-D de 7-byte format di dwuma, bere a Pelco-P de format a ɛyɛ compact kɛse di dwuma. Protocol mmienu no nhyia — sɛ camera no boa Pelco-D na engineering adwinnadeɛ no de Pelco-P ahyɛdeɛ kɔ a, PTZ no rennye mmuaeɛ.

Nea ɛhaw adwene kɛse mpo ne sɛ ebia brand ahorow a wɔde protocol koro no ara di dwuma no wɔ nsonsonoe a ɛnyɛ anifere. Sɛ nhwɛso no, wɔ brands binom Pelco-D implementations mu no, PTZ ahoɔhare encoding no yɛ soronko wɔ gyinapɛn no ho, na ɛde control precision so tew. Wɔ mixed-brand projects mu no, wɔkamfo kyerɛ sɛ wɔbɛhwɛ sɛ protocol compatibility brand biara, sen sɛ wobesusuw sɛ ‘sɛ wɔn nyinaa boa Pelco-D a, ɛne no hyia.’ FangService's PK69 ne PK68 series no boa Pelco-D ne Pelco-P protocols nyinaa, na ɛtumi sesa no ankasa anaa nsa a egyina camera brand no so.

Nkonimdi a Ɛtaa Ba ne Ɔhaw Ho Ahorow a Ɛsen

PTZ control failure troubleshooting hwehwɛ sɛ wɔyɛ nhyehyɛe a ɛsen. Ɔhaw ano aduru nhyehyɛe a wɔkamfo kyerɛ ne: 1 honam fam layer nhwehwɛmu (sɛ ebia RS485 nhama no nni dɛm, sɛ ebia A/B wiring no teɛ, sɛ ebia wɔde termination resistor no ahyɛ mu); 2 protocol layer check (sɛ ebia protocol type no hyia, sɛ baud rate no yɛ pɛpɛɛpɛ, sɛ address code no teɛ); 3 equipment layer check (sɛ ebia PTZ no ankasa adi mfomso, sɛ ebia anyinam ahoɔden a wɔde ma no fata, sɛ ebia mfiri no fã no ayɛ basaa). Honam fam layer huammɔdi ne nea abu so sen biara — A/B line reversal ne ɔhaw a ɛyɛ anifere sen biara efisɛ wɔ nsɛm dodow no ara mu no PTZ no da so ara di akɔneaba, wɔ ɔkwan a ɛne no bɔ abira so pɛ. Bere a woreyɛ debugging no, sɛ wuhu sɛ PTZ no ‘dan kɔ benkum’ bere a ɛsɛ sɛ ‘ɛdan kɔ nifa’ a, di kan hwɛ A/B wiring no. Ɔhaw foforo a ɛtaa ba ne RS485 line multiplexing a idle wire pairs wɔ network cable no mu — sɛ wire pairs a wɔde di dwuma ma RS485 wɔ cable no mu no wɔ twist rates a ɛnhyia ne data pairs no a, signal interference betumi afi mu aba. FangService's PK69 series no wɔ RS485 cable test function a wɔasisi mu a ɛtumi hu cable continuity, short circuits, ne crossovers. Sɛ wɔde ka protocol analysis function no ho a, ebetumi ahunu failure layer no ntɛmntɛm.

RS485 Network Topology ne Akyirikyiri Anohyeto

RS485 bɔs topology ne akyirikyiri anohyeto yɛ anohyeto ahorow a ɛnyɛ den sɛ wobebu ani agu so wɔ mfiridwuma nhyehyɛe mu. RS485 gyinapɛn no kamfo kyerɛ sɛ wɔmfa bus-type topology nyɛ — mfiri nyinaa a ɛne ne ho di nsɛ wɔ line titiriw biako so, a termination resistor wɔ line titiriw no awiei biara. Nsoromma topology (mfiri nyinaa a ɛde ne ho abɔ mfinimfini beae bi) ma nsɛnkyerɛnne a ɛdannan, a ebetumi ama nkitahodi adi nkogu wɔ akyirikyiri mpo.

RS485 nkitahodi kwan a ɛsen biara no ne baud rate no hyia wɔ ɔkwan a ɛne no bɔ abira so. Wɔ baud rate a ɛba fam a ɛyɛ 9600bps mu no, kwan a ɛsen biara no betumi adu mita 1200; wɔ baud rate a ɛkorɔn a ɛyɛ 115200bps mu no, mpɛn pii no, kwan a ɛsen biara no ntra mita 200. Sɛ wɔkyekyɛ PTZ mfiri a ɛwɔ adwuma bi mu wɔ akyirikyiri a, susuw ho sɛ wode repeaters bɛka ho anaasɛ wobɛtew baud rate so. FangService's PK69 ne PK68 series, wɔ RS485 sɔhwɛ mode mu, tumi kyerɛ mprempren nkitahodi parameters (baud rate, data bits, stop bits, parity), boa engineers ntɛm hwɛ sɛ nhyehyɛe no teɛ.

Efi RS485 kosi IP PTZ Control: Nkitahodi Mfiridwuma mu Nkɔso

Wɔde atetesɛm PTZ control di dwuma denam RS485 serial bus so, nanso bere a IP mfoninitwa mfiri reyɛ abu so no, PTZ control renya nkɔso akɔ IP network-based akwan so. Nnɛyi IP PTZ tumi gye ahyɛde ahorow a wɔde di dwuma tẽẽ wɔ ntwamutam nhama no so denam ONVIF protocol anaa vendor-proprietary protocols so, na ɛmma enhia sɛ wɔde RS485 nhama a ɛde ne ho di dwuma no fi hɔ.

Nanso RS485 rennyera nnansa yi ara. Wɔ coaxial HD nhyehyɛe ahorow (AHD/TVI/CVI) mu no, PTZ tumidi da so ara de ne ho to RS485 so; wɔ atetesɛm nhyehyɛe ahorow pii a wɔde ahyɛ mu dedaw mu no, RS485 nkutoo ne ɔkwan a wɔfa so di so. Enti, wɔ IP bere no mu mpo no, RS485 PTZ control da so ara yɛ ahokokwaw a ɛho hia ma ahobammɔ ho mfiridwumayɛfo. FangService no ntwamutam sɔhwɛ adwinnade line no kata RS485 PTZ control sɔhwɛ (PK68/PK69 series) ne IP ntwamutam sɔhwɛ (PK69 series) nyinaa so, na ɛma sɔhwɛ ano aduru a edi mũ ma atetesɛm ne nnɛyi nhyehyɛe nyinaa. Wɔ nnwuma a wɔadi afra a ɛfa nhyehyɛe foforo ne dedaw nyinaa ho no, saa tumi a wɔde kata nneɛma abien so yi som bo titiriw. View the Network Test Instruments Collection