Questions tagged [rs485]

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

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What type of termination resistor to use for terminating RS485 network cable in an electrical room? [closed]

I had visted an electrical room, where the energy meters communicate with an IoT gateway via an RS485 network. The communication uses modbus. I was able to locate the RS485 termination resistors ...
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What technology to use with multiple embedded systems talking to each other?

I am planning on building a system with one master and multiple slaves using MSP430 microcontrollers. The microcontrollers must talk with each other with serial interface using RS-485. I now need to ...
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How is SM712 TVS array suitable for use with MAX485 in an RS485 driver circuit?

I have an RS485 driver circuit consisting of a MAX485 driven by an STM microcontroller. I was looking at TVS diodes for basic protection from electrostatic surges from wiring and handling, and found ...
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RS232 and RS485 sharing same wires

I'm planning a serial port that can either work as RS485 (half duplex mode) or as RS232 (configurable by the user). There are several UART to RS232/485 chips around (like LTC2873), where a GPIO ...
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Can TCC-100/100I Series Industrial RS-232 to RS-422/485 converters with optional 2 kV isolation convert RS485 to RS232? [closed]

I want to convert RS485 to RS232 to connect it to a Moxa Nport 5610 - 16 port RS-232 Ethernet serial device server. Can I use a TCC-100/100I Series Industrial RS-232 to RS-422/485 converter to convert ...
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How to connect RS-422 to 2× RS-485?

I want to connect two Arduinos via RS-422. I have 1 converter RS-422 to TTL and two RS-485 to TTL. How I can connect outputs of my converters (Y,Z,B,A on MAX490 and A,B on MAX485)?
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RS485 isolated or not for home automation system?

I'm creating a home automation system for condominiums. Practically there are a series of control units that communicate with remote sensors. Communication takes place via RS485 serial on an Ethernet ...
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Response partly lost in Modbus RTU over RS485 communication

I have developed a Modbus slave which uses ATMega8A and MAX485. In a new lot of the devices, while testing them on my PC using QModMaster, the response that I get has one byte in front of it, and cuts-...
nottherealfaraday's user avatar
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Can I use LED on the actual RS485 bus?

How bad of an idea is to put a LED on the actual RS485 bus AB lines, for indication of activity on the bus. Something like this: I know people would say why not put LED on 'Recieve' and 'Drive' pins ...
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Pulling Receiver Enable Low for RS-485 Transceiver is being transmitted as a byte in Modbus packet

I am running into an issue where pulling RE low on my Max3441EESA is appearing as an extra byte in my Modbus message. I am currently testing the Modbus capability of my PIC32 MCU with a Modbus slave ...
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RS485 Wiring and Enables

I have an sensor with an RS485 interface that has a pinout with labels V, GND, A and B. In my system context, there will just be this one sensor and an ESP32 microcontroller running on 3.3V to ...
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Connecting a non-galvanic isolated RS-485

I would like to consult if I am designing RS-485 connection correctly without risk of damaging anything. Main goal: I want to get data (e.g. flow temp) from Danfoss ECL 210 district heating control ...
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Is 74244 buffer suitable for multiplying data and enable in my Rasberry Pi3 to ATmega128A bidirectional communication?

My Raspberry sends data at baud rate 115200 to 300 remote panels (ATmega128A) through RS485 bus serial communication. Also it sends enable signal (5 V) and receive feedback from the 300 panels at the ...
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How fast can a Schmitt trigger operate? Can I use it for signal conditioning digital serial data?

I would like to know if I could use a Schmitt trigger chip (e.g., 74HCT14, CD40106B and 74AC14) to clean a 12MHz serial digital signal that has gone through a long cable and will pass through multiple ...
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Potential Reasons for Fault on RS-485 Transceiver

I am working with the MAX3441 RS-485 transceiver, but I have run into faults with the three transceivers I have tested, so I am wondering if anyone can shed some insight on potential reasons for the ...
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Token Passing: Multi Master Protocol Initialising problem

I am into developing a protocol using Token Passing topology. For Physical Layer RS485 will be used. All the nodes will be connected in a daisy chain. No node is initially known the address of the ...
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RS485 wiring - longer or branches?

I read many articles about the RS485, but I still have some questions. What is the better option? Assuming that the distance from one point to another is the same in both cases and the wire is made ...
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RS485 star topology

I have to create a system based on a series of remote sensors that must communicate with a central node. The sensors are all connected with an RS485 bus. Theoretically I should create a classic online ...
Federico Massimi's user avatar
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How should I layout an optocoupler isolation board with separate ground references and power supplies?

I am thinking about how to layout my opto-isolation board. It is used to protect pins on an FPGA, convert signals to RS-422 and then transmit via RJ-45. I have seen some conflicting information about ...
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How should I choose TVS diode capacitance for my 2MHz RS-422 application?

I have been looking at which TVS diode to select for a protecting a set of RS-422 driver lines, however I am struggling to understand how to choose them based on the diode capacitance. The signal will ...
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RS485 from UART of Orange Pi 5 plus

I'm trying to make a PCB "hat" for an Orange Pi 5 plus. What I want to accomplish: 3x RS485 using UART of the Orange Pi and 3pcs ADM1485ARMZ 2x CANbus (already built in). Can I just draw ...
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Problem with Max 485 RS485 to TTL chip (Not Receiving Data)

I am working on a project connecting Arduino UNO r3 and an RS485 modbus master with MAX485. The connections are shown below. ...
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Unable to read data through a MAX485 module

I used arduino code in order to grab RS 485 data from a sensor. The middleman is a MAX485 module. However, I was unable to read the data, even with code that works from previous examples. I hooked up ...
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RS485 Communication Issue: Garbage Values on OLED Display

Hello Stack Exchange community, I am currently working on a project involving two Arduino Nano boards connected via RS485 communication using MAX485 chips. I have set up the connections between the ...
RISHIIII's user avatar
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MAX3362 RS485 IC connection with ESP32

I am using MAX3362 RS485 serial data transfer IC with ESP32. Marked pins 1, 2 and 3 are connected to GPIOs of ESP32. Do I need to add any additional pull-up resistors or some termination resistors or ...
Zunuran Nasrullah's user avatar
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Why is my voltage disapearing from esp32 to RJ45 connector?

I am working on a project where I am sending data from an ESP32 through an RJ45 cable to a DMX decoder. As far as I can tell my wiring is correct, however, I do not appear to be getting the signal to ...
Paul Carlson's user avatar
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Isolate modus IC

I want to isolate the RO, DI, and RE/DE pins going to the microcontroller. Can someone suggest what sort of IC would be appropriate for this application? I wanted to use the FOD8012AR2, however, I see ...
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Trouble to receive data from RS485 encoder in TM4C1294

I am trying to read data from an absolute RS485 encoder Single turn "eCoder-20S". The controller is EK-TM4C1294 launchpad. I am using SN75716AP for converting RS485 to UART conversion. The ...
Muzammil Ibrahim's user avatar
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How should the gas discharge tubes for RS-422/RS-485 be placed and routing on the PCB?

I adjusted the gas discharge tubes to be close to the connectors on the PCB. The RS-422 lines have a differential line impedance of 100 Ω. My concern is, aren't the lines between the connector and the ...
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Can I connect ten RS485 modbus kWh meters to one RJ45 modbus server? [closed]

If I have a fusebox with about ten/fifteen eastron sdm630 and Orno OR-WE-515 kWh meters with RS485 modbus, can I daisy chain ...
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Mid-way level shift in RS485 tranmission

I have two similar devices that communicate using the RS-485 protocol with my ESP32 (through a MAX485 IC). One of them seems to have an issue midway through. Here is the scope image that shows the ...
Adarsh TS's user avatar
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MAX485 module, pull ups for RX and TX

I recently bought the below RS485 module. I see from the schematic they use pull-ups on pins 1 and 4 (TX and RX), can someone explain why are those pull-up resistors needed (R1 and R4)? Secondly, pins ...
JoeyB's user avatar
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Hardware advice for communicating data between two different MODBUS protocols using RS-485

I am trying to build a small device that will act as translator between two devices having two different RS-485 MODBUS protocols. This device will store 4 different values from "Device 1" ...
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RS 485 occasional drop outs

I have been reading a lot on RS485 on this forum and I realised there are a lot of knowledgeable people on here, so I am going to try my luck. I have got a panel installed this panel emits RS-485 to ...
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Twisted Triad vs. Twisted Pair for RS-485

I'm looking for information regarding twisted triad vs twisted pair cable use with RS-485, especially in applications with long distances outdoors. With twisted pair like Belden 3105DB, the drain is ...
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How is the 3 terminal gas discharge tube grounded for rs 422 protection?

I took over an unfinished project. Here, gas discharge protection is used for rs422 protection. 2 different grounds are used in the project. And the middle point of the gas discharge tube seems to be ...
Electronx's user avatar
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Do I need to put a ferrite bead near a RS485 receiver device power pin?

I'm using a MAX3094ECSE+ RS-422/485 receiver receiver datasheet for an application that is receiving quadrature encoder wires. Those wires are power, positive and negative signals from quadrature ...
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Standard pinouts for RS485_interface

Is there any standard DB9 pinout for the RS485 interface? If so please share the same.
Chitharanjan's user avatar
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Why are the TX+ and TX- pins on my laptop's Ethernet port shorted?

I understand that these are supposed to be differential signals with a resistance equal to the characteristic impedance of the cabling between them. However, using a multimeter to check the continuity ...
nottherealfaraday's user avatar
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Differential Pair Data Transmission for Larger distances

One of my client wants RS485 data from my remote field instrument to their control panel which is around 3km away. I know, RS485 won't work for such distance. Converting RS485 to optical signal will ...
Harish Kr Singh's user avatar
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What is the operation of this RS485 transceiver having this connection?

I am confuse with the R1 and R2 function. The "Direct Connection" wire is connected to another transceiver's DE/RE. When the DE/RE is high, driver is enabled, and when the DE/RE is low, the ...
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Switching RS485

I'm using RS485 on an Arduino with a MAX485. The comms goes out to a two core loom, but I need to use the same loom for two purposes (non simultaneously): Provide power to a device RS485 ...
HemiMan's user avatar
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Why does voltage in RS485 bus change significantly when termination resistor is connected?

I've set up the following simple, non-terminated RS-485 network: The bus is 10m long CAT5e cable, carrying a 4800 baud signal. RS-485 transceiver (TRX) is an XY-k485 module (MAX485-based). ...
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Single ended output voltage of RS-485 transceiver

I am designing an RS-485 bus using TI's SN65HVD17xx transceiver. I am trying to calculate the voltage drop along the bus and what voltage the last transceiver on the bus sees, in order to find the ...
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Can USB-to-SERIAL dongle be used to drive an RS-485 transceiver?

Pictured below is a simple arrangement used to read the Temperature sensor from the PC. Standard/Protocol is MODBUS RTU RS-485 Half-Duplex. I've used this arrangement with both modpoll.exe and ...
Noideas's user avatar
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Modbus receiving same message as sent

I am having a problem when communicating with a Modbus slave. I have made a circuit with the translator shown in the picture. UART2_RXD and ...
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RS485 not working

I want to send data between different Arduinos distributed in different places: Something like this: https://forum.arduino.cc/t/arduino-master-slave-communication-using-rs485-and-modbus-protocol/...
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Reason to have MSB in a serial communication always high

I'm working on a code (written by other people) that uses a custom protocol to transmit data over RS485 in 8-bit packets. For some reason, the protocol is built so that every 8 bits transmitted are ...
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How to reduce noise on RS485 line?

The above picture is the output of a MAX485 IC, which is an RS485 transceiver. When the Cable comes near an AC power line, this kind of noise adds up. Without the presence of the AC main line, its ...
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Is there any way to convert RS485 to K-line (ISO 9141)?

I'm trying to build a touch panel interface based on a WT32-SC01 PLUS to control my Webasto heater. The WT32-SC01 PLUS contains an RS485 interface and I would like to know if it is possible to build a ...
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