Questions tagged [rs485]

EIA RS-485 is a serial communication standard using differential signaling.

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38 views

Is the RS485 common mode output voltage supposed to be only 3v

I am designing an RS485 driver to connect to an ESP32 using SP3485 from Max Linear. I understand that the differential output is 3v and not +7v and -5v like the RS485 spec stipulates. Are there some ...
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Star configuration using CAN Bus, I2C or RS485

I need to create a sensor network, with a central node receiving data from +10 different nodes, each one +20meters from the central node. So basically I need to create a star configuration, with a ...
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RPI Linux RS-485 with CH340B chip (Sometimes misses 7th byte, on specific reading)

I have a problem with RS-485 communication. Sometimes reading misses 7th byte (so it misses start bit). It happens only on specific reading (position of elevator 529 +-2). Otherwise is communication ...
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53 views

TTL into RS 485 transceiver

I have a TTL signal that I am unfortunately trying to send into an RS 485 transceiver (PXIe 6584). I thought I could be clever and connect a transmitter port to the negative end of the RS-485 receiver ...
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41 views

Implement RS485 or I2C protocol using the usb-c connector?

I was wondering if there's any reason why I can't implement RS485 or 12C communication on the data pins of the USB-C connector? I can't find anything on the internet that tells me not to.
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RS485 isolated circuit - forgot connections. Will this work?

below is my schematic for isolated RS485 section. FYI B0305XT-1WR2 is used for power isolation and ISO1500DBQ as transceiver. As you can see I forgot to place GND & GND_RS485 connections at pins 2 ...
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58 views

Terminating resistor considerations for half-duplex RS-485 over 80-200 m cable at 115 kbps

I'm designing a system where we are communicating with a device (ultrasonic anemometer) which is at the end of a cable which could vary between 80-200m. The sensor communicates via RS-485 half-duplex. ...
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The Best Place for the Reverse Polarity Protection Diode

I have several RS485 devices. All of them are connected together and power by a 12V power supply. Each device has its own 5V voltage regulator. I want to use diodes for each of them to protect aginst ...
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52 views

CAN Bus with RS485 CAN HAT for Raspberry PI

I have set up a CAN bus between 2 STM32 Nucleo's, where one is only sending messages and the other one is only reading them. This works, I have also validated this by connecting them to another CAN ...
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1answer
36 views

RS485 unmatched line - what will be the impact?

I am doing an experiment where I have a computer with an rs485 transceiver on it and data rate of 1Mbs. an rs485 30m long with Z0 of 120ohm (also have one with Z0 100ohm). at the end of the cable I ...
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64 views

Using RS485 over CAT5e Foiled Twisted Pair (FTP)

I'm planning a system that has two sub systems that need to communicate with the PLC via RS485. The baud rates are 9600 and 19200 bps. The cables are static (i.e. not moving) and placed inside of a ...
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USB Solution to Bit Bang RS485 at a high Baud Rate

I am searching for a solution to write a ~800 byte data stream at a 10K baud rate from a USB device. This is going to connect to a piece of hardware that uses a RS485 connection which expects an ...
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RS485 Communication Issue Adm2483

I have Setup like this for my application. I have Transformer which gives out 12V 1A & 5V 500mA output.I have used isolated ADM2483 design where power galvanized isolated. Primary side 5v &gnd ...
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68 views

RS485 burnt slaves after short-circuit

I have a question regarding a scenario I found myself in, hoping that someone can clarify if the scenario I'm going to illustrate is possible (short premise: I'm a programmer, I'm not an electrician ...
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55 views

Transmission lines in paralell for RS485

I have a system with two RS485 transceivers connected by a 300 meters long cable, with 6 wires inside it. In this case, 3 paralell wires of this cable are being used for the "A" signal and ...
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how to connect PIR sensor to arduino using RS485

I have to connect PIR sensor HC-SR01 to Arduino using RS485 such that PIR sensor's TTL signal gets converted to RS485 while transfer and gets converted back to TTL while receiving on Arduino side. ...
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47 views

how to verify truth table of MAX485/RS485

I want verify 2nd case of the below truth table of MAX485 IC (RS485). Please see in red color. Is my circuit correct ? I have connected RE,DE and A-B to GND for making it LOW.I have connect DI to GND ...
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RS485 implementation using MAX485 chip

I am using MAX485 chip for serial communication. But a weird behavior I found which I can not explain. Can any one help me in understanding why LED is ON in Receiver pin (RO) when I have not given any ...
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1answer
62 views

Bus communication scheme for large number of devices (255+ nodes)?

I'm trying to figure out the feasibility of setting up some type of differential bus communication for up to 400 devices outdoors. The main constraints are mainly power consumption, complexity, wire ...
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59 views

How to identify the polyfuse used in this RS-485 module

This is the popular RS-485 module found in the market, how can I identify the polyfuse/heat recovery fuse in it? Also its manufacturer or electrical ratings?
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1answer
59 views

RS485 communication issue

I have used PIC18F45k40 device for RS485 communication. I have 2 ckts one is isolated and another non isolated RS485 design. I have schematic & placement for reference. I have connected multiple ...
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1answer
36 views

RS485 Communication- board Hangs

I am using isolated RS485 for communication. MCU & RS485 IC communication is through UART. IC supports 500kbps datarate Configuration a) Baud rate- 460800 b) Every 0.1s I am sending 288bits data ...
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51 views

Grounding in CAN / RS485 Busses

I'm interested in how to properly realize Grounding in a CAN / RS 485 bus setup. From my understanding, when non-isolated transceivers are used, in addition to the differential signal lines, a third ...
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84 views

RS-485: what happens when bus contention occurs

I'm refering to an half-duplex RS485 application which consists of a master and multiple slaves like in the circuit below (I'm using an ST3485). simulate this circuit – Schematic created using ...
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RS 485 communications not working, A, B both low

My question is: for RS485, does A or B (one of the two) have to be HIGH by default? If there are only 2 communication nodes in the network, should one of the nodes pull A or B (one of the two) HIGH by ...
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Sharing Isolated Power supply for CAN and RS485

I am using ISO1432 from TI for isolated RS485 transceiver function. And ISO1042 for Isolated CAN transceiver. Both devices requires an isolated supply on bus side. Can I use one isolated 5V DC-DC ...
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Communication within 5-10 meters: RS-485 or Wireless?

As a follow-up for my previous question, can anyone please recommend for my application (communication between two floors of a building) as whether to use RS-485 or any wireless technique (I am ...
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Transmitting VCC and GND signals for use with RS-485

The specific question I want to ask is whether I can transmit VCC(5VDC) and GND power signals for powering the destination circuit (in an RS-485 arrangement) or not. The power lines will be grouped ...
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46 views

Why Arduino not receiving RS485 data?

I am trying to send data from Arduino mega (message "ping") to Arduino nano, then send back (message pong) to the mega board, I am not receiving "pong" back to the mega board, why ...
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55 views

RS485 over CAN: when and why?

I'm designing my own home automation gateway and I've already added a rs485 transceiver, everything is fine, but I'm thinking about adding also a CAN bus transceiver because I've seen that it's often ...
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89 views

Pull-up and pull-down resistors for RS-485 TTL I/O pins

I'm Using a THVD1451 for full-duplex RS-485 communication. In Datasheet, for transient protection against surge transients, it's recommended to use the circuit below: In this circuit, there is a pull-...
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where should I place the terminations resistors for RS485?

I want to add termination resistors in RS485 bus . My systems is Multi-point ( the MCU can send to/receive from 3 external devices) I found out from this RS-485 CABLE SPECIFICATION GUIDE. that I need ...
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What is the max current consumption on bus side of isolated RS485?

application - 10 nodes 1 meter apart 120 Ohm terminating resistors at last node and 1st node i hope to use ADM2486 data rate 10-17Mbps vdd1 5V and isolated vdd2 5V what is the max current consumption ...
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49 views

withstand voltage of RS-485 Transceiver

i am working with a half duplex RS-485 Transceiver ic SP3485EN with 10Mbps Data Rate datasheet :https://www.maxlinear.com/ds/sp3485.pdf i actually want the maximum working voltage (Viom) of design ...
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67 views

RS485 USB converter driver polarity

I have an RS485 USB converter connected with a temperature controller in the controller's datasheet it says that the 12 is (+) and 11 is (-) and in my USB converter there is A and B Am not sure the D+...
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Generate spikes on RS485 bus

I was thinking to build some test equipment for a RS485 bus, but Would like to get some suggestions on how I can introduce bursts of spikes in a "safe" way without damaging the connected ...
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Isolating an existing RS485 tranceiver

I have a heat pump with an RS485 interface. Via a simple RS485 chip. No isolated interface, no isolated power supply to it. I want to add a power meter at 400+ meter to it and want to properly isolate ...
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Bi-Directional RS-232 / RS-485 translator using MAX3162 IC [closed]

I'm trying to communicate with an I2C bus using the Serial Card in my PC (NI PCI485/8). I've created a circuit using the MAX3162 to translate from RS485 to RS232. Then I use the MAX3232 as a level ...
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SN75176A in full duplex application

I am trying to interface with an RS485 device (laser) that is full duplex (115.2k). I am using two SN75176A ics... I can receive data from the laser fine, but I can't transmit any data to the laser. ...
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1answer
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Printed circuit board connector identification

I have a PCB with some connectors and wanted to identify which type there are of. How do the experts approach the problem, to identify the type? For example, the picture below shows a connector, ...
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RS485 slew rate limiting remove need for termination

In regards to the highlighted feature of "slew-rate limiting" RS485 ICs. It says in multiple brand datasheets that the slew-rate limiting helps with transmission errors when there is ...
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Connecting 50 Arduino slave devices to a single master Raspberry PI

I am designing a automation system and need to have multiple slave devices(probabaly arduino UNO or NANO) communicating both ways with master device (Raspberry PI). There is a server and database ...
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1answer
90 views

SC18IM700 operation (RS485 to UART to I2C)

I need to create a circuit to talk to a piece of equipment using the I2C bus. I'm on a PC that has an NI serial card with RS485 ports(I'm not sure of the model number off the top of my head). I ...
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RS485 Input Hysteresis

What is the meaning of Input Hysteresis in the context of a RS485 transceiver? Thanks
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RS485 Trancievers: ADM2483 VS ISO15

i'm actually doing some hardware selection about RS485 trancievers. There are a lot of different suppliers, drivers, etc... So, i've selected these two trancievers: ADM2483 from Analog Devices and ...
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Glitching on UART RX line with RS485 transceiver

I have a custom PCB which has a RS485 transceiver chip interfaced to a Nordic microcontroller. I essentially have a daisy-chained arrangement of RJ-11 ports which are carrying the RS485 A/B signals as ...
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How are DC offset square wave transmission waveforms generated?

The balanced serial transmission shown in the picture is similar to rs485 except that the square wave has a DC offset (e.g. 24VDC) with an alternating offset. The transceiver chip "drives" ...
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95 views

RS422/RS485 termination and noise immunity

Consider a RS422/RS485 receiver like the AM26LV32 or the DS26LV32. It is used to receive the signal of incremental encoders with differential outputs. Assume that those are using drivers such as the ...
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Switch “On”/“Off” RS485 data lines

i'm doing some researches about how to close/open RS485 data line in my RS485 multi device bus. I'm following this nice research-document: Link Here. Basically i'm thinking how to solve this problem ...
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RS485 transceiver design: Bias, termination, filter and protection

For the realization of an RS485 transceiver, I came across the question: How can bias, termination, signal filter and protection be best implemented in one design? In my case, one RS485 master (with ...

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