Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [rs485]

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

1
vote
2answers
72 views

Switching of RS485 differential line. Two sources, one output

I'm looking for a solution for my project. I have two signal sources (primary source and secondary source) on the RS485 (A/B) differential line. When/if something goes wrong on the primary, then I ...
0
votes
1answer
45 views

RS422/RS485 data input series resistor

I am using an RS422/RS485 driver to send Arduino 5V logic data over longer distances. I use the SN75174 driver for this purpose. In order to avoid ringing, I am not sure if I have to connect a series ...
2
votes
0answers
102 views

Reverse-engineering RS-485 communication

I've been trying to reverse engineer the communications protocol used by my home domotics, which I was able to determine uses a RS-485 implementation. I'm using a USB RS-485 serial dongle and an ...
1
vote
0answers
48 views

RS485 full duplex to Adapter with A and B ports

I need to configure a sensor (Thies 3D Sonic Anemometer, Manual: https://www.biral.com/wp-content/uploads/2015/01/4.383x.xx_.xxxUS3D.pdf) via my computer, it has RS485 full duplex and half-duplex ...
2
votes
1answer
43 views

Relay+SMPS = Noise in RS-485 bus

I designed a board with a microcontroller (Atmega328), 3 relays and a RS485 transceiver. The relays control SMPS LED drivers (Meanwell LPF series). The system consists of 10 boards, each one ...
0
votes
1answer
43 views

J1708 (open collector RS485) at higher baud rates than 9600 bps?

I have here a PCB which has a kind of "open collector" RS-485, known as J1708 (schematic attached). The default baud rate is 9600 bps and there is no terminators, J1708-TX is a 3.3V signal. I would ...
1
vote
1answer
30 views

RE: Receiver Output Enable and DE: Driver Output Enable pins

Hello I am planning to use LT1785 UART-RS484 transceiver. I will use that chip in order to get RS485 data and convert it to UART signal. So I have read the datasheet but I couldn't be sure. It says ...
1
vote
2answers
64 views

Rs485 to UART convension

I need to send data from one PIC to another PIC by using RS485. As a protocol I use UART. However, I cannot be sure about RS485 transceiver and its circuit. I will be able to supply 5 V and according ...
0
votes
1answer
47 views

Transmission distance rs485 vs ethernet

I have a question, why is rs485 limited to less than 100 meters at 10mpbs ( mbaud ) and is 100Base-TX ethernet applicable on 100 meters with 100 mbps bitrate i know that rs485 normally use a sort ...
7
votes
2answers
613 views

Effect of “wrong” driver with slightly long RS-485 stubs

I have a planned 250 kbit/sec, single-pair, 36-metre RS-485 installation where it is advantageous for wiring purposes if the stub lengths can be a little longer than optimal. There is a single almost-...
0
votes
0answers
38 views

RPi USB to Serial testing

I have a system like this: RPi -> FTDI(USB UART IC) -> RS485 transceiver -> RS485 TO USB board -> PC I'm having some trouble testing RS485 communication between the RPi and the PC. I'm using a simple ...
2
votes
1answer
533 views

RS-485 using USART or UART port on STM32

On STM32F405 MCUs there are USART ports as well as UART ports available. If I need to implement RS-485 communication then which one of these should be used, USART or UART? Or are both of them equally ...
0
votes
1answer
27 views

SN65HVD3x (RS485 Driver) - Termination resistor

I want to use the SN65HVD31DR to connect two microcontrollers together. The connecting cable has an impedance of Z0 = 80Ω. According to the data sheet it is recommended to terminate the connection ...
0
votes
1answer
52 views

How do you monitor communications on a positive-grounded device from a negative-grounded desktop?

I have a need to read the signals being sent between two boards in a lighting fixture. In preparing to do this I have read much about the chips, RS485, and analysers/decoders that are out there. I am ...
0
votes
2answers
107 views

RS485 vs RS232 similarity vs differences

I have used UART RS232 communication between MCUs extensively. Now I need to interface my STM32F407 MCU over RS485 bus with with devices. I have understood few things about RS485 but not-clear about ...
0
votes
2answers
82 views

Medium Range Two Wire Bus Recommendations?

Do you have any recommendations for a medium range (~10 meters) two-wire bus? My supply voltage is 24V and I'll have a single master with ~50 slaves connected to it. I've looked into: I2C - Great but ...
1
vote
0answers
25 views

Signal Attenuation TVS and series resistor

This question is in regards to signal attenuation on high speed data lines like RS-485 (and any others as well). I'm new to the signal world, so please bear with me here. Are there some useful ...
0
votes
1answer
50 views

RS485 Rx signal connected with two drivers

I wonder why is RS485_Rx is connected with two line drivers while RS485_Tx is connected with only one line driver. Is this some mistake in the schematics or is it some standard circuit for RS485?
0
votes
2answers
91 views

Multiple MAX3485 on same UART

I am working on a project where I have 4 MAX3485 (for 4 different RS-485 channels) chips talking on the same UART bus with an ESP-WROOM32 module. This is the schematic: simulate this circuit – ...
0
votes
2answers
72 views

How to select the most appropriate (serial) bus for controller?

In the context of a robotic project where different 'payloads' and/or robotics arms (end-deflector) should be mated mechanically with power, data and control connections support, I would like to ...
1
vote
2answers
98 views

RS485 line protection diodes

Can anyone confirm the correctness of D27, D28 diode polarities or should they be in opposite direction? Please suggest an which diode is suitable for this purpose OR is it better to use a zener diode ...
4
votes
1answer
366 views

Does a MAX485 need decoupling capacitors?

I am designing a small device with two MAX485 chips. Do they need the decoupling capacitors on the 5V power?
3
votes
2answers
94 views

RS-485 Stub Connection Best Practices

I have a system with an RS-485 bus master and up to 12 slaves. The master and slaves are located in different assemblies and are connected with an RS-485 bus that is inside a cable harness. The cable ...
0
votes
1answer
58 views

Is it acceptable to have A & B wire at same voltage in RS485

I'm trying to implement DMX with a Raspberry Pi after reading this page: https://www.element14.com/community/groups/open-source-hardware/blog/2017/08/24/dmx-explained-dmx512-and-rs-485-protocol-detail-...
0
votes
0answers
38 views

DMX protection circuit (diode clipper)

TL;DR I’m building a board that bridges the common types of DMX connector (various forms of XLR, RJ45, tails and product-specific terminals). There is a possibility that someone could accidentally ...
1
vote
1answer
60 views

To Fail-Safe or not Fail-Safe on RS485/422 Transceiver

I'm stuck on a PCB design issue. I'm designing a new PCB (Daughter board) that will plug (via DB15-F to DB15-M) onto another PCB (existing Mother board) and the design intent is to take (from the ...
1
vote
1answer
73 views

Wireless or wired solution for perimeter fence security?

We are currently working on a project where we would like to place around 350 vibration sensors on our university's perimeter fence for security. The field layout is almost 1km to 1km (square - 1km^2 -...
1
vote
1answer
103 views

Rs-485 isolation

Hi, I have RS485 communication circuit as shown in figure. But it has no isolation, only SM712 is used for ESD protection. Now, i think it will be better to isolate the it.So, how can i isolate it? ...
0
votes
0answers
113 views

Why is there no reponse from ModbusRTU slave using converter?

There are two devices: Eaton EM20/M (~like Northern Design Cube 400) Volison ADM-5850G Connected them like: Trying to get data from EM20/M which supports ...
2
votes
2answers
68 views

RS485 termination

What is the recommended way for termination RS485? I read about couple of options to do this. If I don't want to do dissipate extra power, can I just put 120 Ohm resistor? I saw the follow ...
2
votes
0answers
63 views

RS485 registers for calculating total power consumption (kwh)

I have an energy meter (OHIO A2000) which has been now discontinued by the manufacturer. Anyway, I'm following the manual for extracting energy parameters through Modbus RS485 communication. I'm ...
0
votes
5answers
96 views

RS485 IC Termination Resistor Configuration

I've made a mistake on a design, that went into production... It was built like the drawing on the left, with R702 to 5V and R703 to GND, it should have been backwards... like the drawing on the ...
1
vote
1answer
37 views

Low current rs485 and wake up

I have the following question: I have to do a network of devices based on MCU. This network in a RS485 and the device is battery powered. For save the battery I put in sleep mode the MCU and I ...
0
votes
2answers
78 views

LIN to RS485 and back to LIN

I am currently communicating between two microcontrollers using a single pin and the LIN protocol over a short distance of 0.2m. Now I would like to extend the distance up to 5m by differentially ...
0
votes
3answers
226 views

ground connection for isolated rs485 [closed]

Is it necessary to connect isolated grounds for 2 different isolated RS485 nodes? For instance the following isolated RS485 breakout board doesn't have any GND connection in the board. https://www....
0
votes
2answers
401 views

Connect RS422 interface with Arduino Uno

I have a fishfinder,Lowrance Carbon HSD 7, and I want to connect it with the Arduino Uno to let the fishfinder transmit the Sonar data and GPS data via NMEA0183. According to the maker's site, the ...
0
votes
1answer
153 views

ModBus Timeout Error

Anyone very experienced with Modbus & RS-485??? My task is to control a DC motor using micro PIC24. The motor setting like the angle, delay, start/stop, duty cycle, etc will be sent from PC using ...
1
vote
1answer
124 views

RS485 Waveform while Receiving Data

I was testing the RS485 Circuit, below is my circuit and I connect J5 to my PC using another RS485 to USB converter. In PC through Modscan software I was monitoring the polling and response, a twisted ...
0
votes
2answers
61 views

I need to switch between RS485 signal and Digital input port

I am looking for a solution where I can use RS485 along with the 2 (two) digital input port on the same line but both will be used one at a time. When there is RS485 communication (selected through ...
1
vote
1answer
94 views

MAX485 suddenly drawing too much current and output voltage levels are not right

I have two PCB that I designed and they are made by a PCB manufacturer (so they are identical). They use a MAX485CSA to communicate but suddenly one of them is drawing too much current, on a normal ...
0
votes
2answers
66 views

Differential signal isolation

In differential signal circuits (specifically, RS-485), there is usually an isolation between the signal processing / generation stage (eg, microprocessor) and the line driver chip (something like a ...
1
vote
1answer
88 views

RS-485 works when USB powered, not when main powered

I'm thinkering with a RS-485 connection (modbus) to read out my electrical power meter. The setup is as follows: ESP32 --> MAX3485 --> RS-485 to USB when the ESP32 is powered via USB, on the same ...
0
votes
1answer
53 views

Arduino RS485 Communication

Working on a RS485 IC circuit. It is a point to point communication between two devices connected to each other via MAX485 IC and CAT6 Cable. At 1 or 2 m length of cable, the data transfer seems ...
0
votes
2answers
120 views

How to determine the physical location on a RS-485 daisy chain / bus topology?

I am trying to build a "daisy chain" using several Arduinos and MAX485 transceivers. All boards have a temperature sensor attached to it. A 9V battery supply all boards in the chain. I am trying to ...
0
votes
2answers
62 views

Where to use CAN v RS485

Not sure whether this is too broad a question but... Why would one choose CAN Bus over RS485, or vice versa, as a system interconnect? I have a MCU SBC with multiple interfaces including the two ...
0
votes
2answers
168 views

RS485 transceiver design

I'm working on a TTL to RS485 transceiver which is part of a bigger project (arduino based) and I came up with the following design: I have a few questions: 1) I have seen very different values for ...
1
vote
0answers
36 views

Addressable RS485

I have a requirement to take a board that interfaced with RS232 and put it on a half duplex RS485 bus. The obvious problem is that at the very least the board firmware will need to be altered to be ...
1
vote
0answers
56 views

Looking for data sheet of the following Modbus Sensors #updated

I'm a noob in this area, please ignore any stupidity and lack of info and any help is appreciated and I'm ready to provide all clarification on the post if by chance any info is missing. So i have ...
0
votes
1answer
129 views

What is 8 pin tssop packed component?232/485 ethernet converter

-size = 2.9mmx3.1mm -GND pin = 1,6,7 connected -7.pin 4.7uh connected
-1
votes
2answers
75 views

What communication method shouild I use [closed]

So I wan to control a bunch of devices. I though first of using RS485 but after some digging I figured out this might not work as I don't really have a pure daisy chain. The configuration I would like ...