Questions tagged [rs485]

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

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How to wire up GSM Modem(DCE) With MAX485

I am trying yo figure out how to directly connect a GSM modem (say SIM800) with a MAX485 . The purpose of this is to make an RS485 GSM Modem. I am struggling how to wire it up, do i wire the CTS of ...
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XPort Edge (web manager) access denied with default credentials

I have the Xport EDGE connected and powered using the evaluation board. I'm trying to use an XPort EDGE as a means of connecting an embedded device to the internet. It uses RS485 (That's the ...
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1answer
44 views

GSM Module + RS485 transceiver possible?

I was wondering if someone could confirm if it is feasible to interface a GSM module for example SIM900, SIM900, Quectel's M95 or Neoway's N10 , maybe if we use the RS232 interface with HW the flow ...
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54 views

RS485 communication between Arduino

I want to transfer data (only numeric values) between Arduino Nano and Arduino Mega 2560. I tried with my own code and tried with several libraries also. Arduino Nano code ...
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Noisy RS485 signal with MAX13487E and Raspberry Pi

I am trying to use the MAX13487E RS485 transreceiver with a Raspberry Pi 3 B+. I chose this chip specifically because it does not require a RTS signal, which is complicated to setup on the PI. My ...
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Replacing the physical layer of MIL-STD-1553 with RS-485

I've been reading about MIL-STD-1553 buses, which very briefly are multidrop Manchester-encoded 1 Mbit/sec 32-station: a single "bus controller" master and multiple "bus terminals" slaves which speak ...
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1answer
104 views

Decoding an unknown serial bitstream that does not fit 8-N-1

I am looking at an RS-485 signal using a scope and an analyzer (saleae). This is running a mystery bus (see below for more information). I would like to know how to fix my frame errors. I can't begin ...
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RS485 Common Ground: Common Voltage or Common Wire or Both?

RS485 connection needs a common ground, but I am very fuzzy about how that works over longer distances and more complex systems. When the transmitter and receiver are about 1000m apart, there will be ...
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125 views

RS422, RS485 Termination Resistors

While going through this youtube video from TI about the RS232, RS422, RS485 differences. One thing that don't understand clearly is following slide from this video. The blue resistors that I marked ...
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59 views

RS485 - Comunication lost during EFT IEC 61000-4-4

I'm having throubles with communication over RS485 in harsh industrial environment. We perform test in EMC lab, acording IEC 61000-4-4 = Fast transient (also known as Burst). We used burst generator ...
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1-channel GPIO from industrial PC over RS232 port

I am ordering a computer based on 4x4-R1000V motherboard (Ryzen Embedded, https://www.asrockind.com/overview.asp?Model=4X4-R1000V) for an industrial application. I need a 1-channel GPIO (0 for zero, >...
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Please help me understand modbus communications

I'm just starting out with understanding how modbus works over a rs485 protocol. I've received a communication protocol document from a company that makes solar inverters. I want to send a command ...
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126 views

Isolated Modbus (RS485) ground and UART noise

I build an isolated RS485 (Modbus) interface board for a sensor. I use ADM2682 as transceiver and VAQE6W-Q24-S12-D as isolated DC-DC converter. All is managed my a STM32L412. There is 2 interesting ...
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49 views

How would I connect an HC-06 bluetooth module to an SN75176A RS-485/422 transceiver?

I am trying to fashion a small module that would allow me to connect to an RS-485 system via Bluetooth. I have found that the potentially cheapest solution would involve an HC-06 TTL Bluetooth ...
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1answer
40 views

Modbus: Sensors timed out when plugging another sensor

I have created an hydroponic system using modbus to communicate between a RaspberryPI server and plug&play arduino sensors. It works but as soon as I plug a sensor on the bus (physically), all the ...
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Questions on connecting and using the RS485 MAX14783E transirver

Task: Using Arduino UNO, obtain various parameters from the ABB B21 112-200 electric energy meter, as well as send settings to it. This meter has an RS485 interface (ModBus RTU) with terminals A, B, ...
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How to connect a few shields correctly?

There are several shields on my PCB: shield on CAN-bus, on RS485, on Ethernet, on ENCODER motor signals. How do I correctly connect all these shields? If I use the star topology, which filters should ...
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83 views

Is this a reasonable setup for terminating and protecting an RS-485 transciever?

I'm working on a design where an RS-485 transceiver IC is connected to a Cat5e cable, hopefully at 96k baud at a distance of up to 150m. I'd like to offer some protection in the design, but I've never ...
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1answer
40 views

MAX485 problem on signal with Arduino

I'm trying to do communicating an Arduino Mega to an Arduino Nano through RS485 protocol. In this way, I'm using two MAX485 boards like this : If I apply this wiring : I get this signal : As you ...
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How to connect an SPI angular sensor (AVAGO AEAT-9000-1GSH0) with RS485 transceivers to an AVR microprocessor?

I need to connect an AVAGO AEAT-9000-1GSH0 angular sensor to an ATMEGA32U4 processor. I designed two versions: one using IC-s, one using resistors. I do not now witch of my two designs is better (or ...
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Modbus RTU over RS232 link

I am designing a convertor board that will interface three device with Modbus RTU RS232 port to a Modbus RTU RS485 network. Slaves supports Modbus RTU, but their ports is different from master port. ...
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How can I connect multiple modules/devices to one single usb port

Currently I have one GSM IOT-GA6 module connected to my laptop using a CP2102 usb adapter. Currently im able to communicate with the device sending AT commands using ...
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2answers
57 views

Is this way proper to create differential inputs from a function generator for this setup?

I have soldered an RS485 to TTL converter on a board and want to test it. The thing for a test, I need differential inputs as DATA+ and DATA- and I don't have a sensor which outputs differential ...
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2answers
64 views

RS485 transceiver supplied with 3.3V. What voltages can I receive?

I'm designing a print for RS485 with the LTC2854 transceiver, but I don't know in what exact situation it will be placed in. So I don't know what voltage levels the other devices will communicate on. ...
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456 views

Is a ground connection needed in between master and slave for this RS485/422 scenario?

I will work on a small project where an SSI-output data (angle data) of a rotary-encoder will be read by a micro-controller board (such as an Arduino board) and the micro-controller will then send ...
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74 views

RS-232 to RS-485 transceiver

I'm new in communication protocols and ICs. I would like to know if it is possible to connect a RS-232 (TX, RX and GND) to a RS-485 (Vcc, A, B and GND). I only need a half-duplex communication. The ...
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1answer
60 views

Multiple Terminating Resistors on RS-485 Bus

I bought this TTL to RS-85 board and before connecting it to my Arduino I decided to double check (reverse-engineer) its circuit and I can see there's a 120 ohm resistor between the A and B outputs. ...
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57 views

Trouble connecting to temperature controller using MODBUS,RS485 and MATLAB

I am trying to communicate with a temperaturature controller ATR-401 using MATLAB but i am having trouble just connecting to it and reading temperature data.I have set baud rate, data bits, parity and ...
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Read Data from Temperature Controller using MATLAB, Need Help

I am trying to read data from a temperature controller called ATR-401 using MATLAB's tool box called Instrument Control Toolbox but every time i try to read data from it i get an error "A timeout ...
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115 views

RS-485 to USB converters (cable conversion)

I am working on a project that involves a Solar Charge Controller. The device ships with an Ethernet RS-485 communication interface as well as a RS-485 to USB cable, which is said to be able to ...
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149 views

RS485 entering and leaving a PCB

For architectural reasons, we have a need to take a twisted pair (of an RS485 bus) into a PCB and then out. The PCB traces would add about 2 cm (just less than an inch) of length to the bus. The stubs ...
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133 views

RS485 Eye diagram - does it look good?

I got a new diff probe, I am trying it out on RS485. I'm triggering on the rising edge. The RS485 is running at 25Mhz. Does the eye diagram look good? Could I double the speed (50MHz) and be ok? (...
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70 views

noise on RS485 with MAX485 on short line with biases

I am connecting an industrial device (controlled over LAN) with RS485 output signal with Arduino via MAX485 board. I connect the RO (receive out) pin of the ma485 ...
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1answer
71 views

How to identify 422 or 485 bus from the PCB

I have a very old CPU card, maybe 1980's. It has following chips on it and most probably these are used for communication with the rest of the system. SN55188 Quad Line Drivers SNJ55189 Quad Line ...
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66 views

Interfacing LEDs at communication lines for a RS232 to RS485/RS422

I want to use LEDs at the output of R232 to RS485 & RS422 converter to indicate the Rx and TX activities. This converter will be inside an enclosure and I want the RX TX activities to be indicated ...
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Detecting Communication Frames

I am sending data between a master and several slaves with RS485 with bytes (8 bit) messages with a very simple frame inspired on Modbus ASCII: ...
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170 views

Can RS485 be considered a multi-master bus?

There are some electrical specifications specifically designed for multi-master protocols such as CAN, I2C, 1-Wire, etc. which are classified under CSMA/CD networks. However, RS485 has a push pull ...
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51 views

Serial communication for Arduino Mega with RS485 and FTDI using the same TX data line

I need help with the following problem. I have an Arduino Mega in which I connect several devices that occupy the 4 TX and RX ports that this Arduino has. I need to connect an RS485 to the Arduino and ...
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Providing RS-485 ground when no pin is provided

I have a PC with an RS-232 to RS-485 converter controlling (@ 9600 baud) a large piece of HVAC equipment in an adjacent utility room, <50' away. We are adding two more of these pieces of equipment,...
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Confusion about TVS-wiring with RS-485

I'm currently looking into securing my RS-485 connections against ESD. My current understanding is that a TVS diode is put between the data line and GND, so that any discharge will be shorted to ...
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143 views

RS-485 network with multiple masters

I'm building a project with multiple RS-485 senders ("masters") and one receiver: simulate this circuit – Schematic created using CircuitLab I'm using one MAX485 as receiver connected to a ...
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PCB Power Divider Tee for RS 485

For a RS-485 Communication using a Maxim MAX3292 Driver, Full Duplex, 1/4 load unit (54 \$\Omega\$), 5 Mbps, with UTP 120 \$\Omega\$, standard cable, for each receiving unit I am thinking on a design ...
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2answers
145 views

Reverse-engineering RS485/Mechatrolink-II front-end design

I'm trying to reverse-engineer Mechatrolink-II front-end circuitry. Its physical layer is simple RS485 (with isolation transformer) running at ~10Mbps. Here is the schematic I obtained from the PCB of ...
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1answer
266 views

RS422 and RS485; full-duplex or half-duplex?

I have extensively used RS232 transceivers in many projects and have fairly good understanding of UART communication using RS232 transceivers. MAX232 and MAX3232. Now I have to build my understanding ...
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What is the difference between a multiplexed bus and a multi-master bus

The jargon of terms in bus architecture literature is half the difficulty in understanding it. At some places the term 'multiplexed' bus is used while at some other places 'multi-master' bus is used. ...
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Protecting MAX485 data or supply from shorting to 24v DC supply

I have 2000 infrared proximity sensors along 100 meters, divided to 2 meter sections with an arduino reading them sending results by MAX485. For the power, I am supplying same 24v dc from each end of ...
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72 views

Why less protection on a GPIO RS485 board compared to an UART RS485 board?

When I search for RS485 board (to be used for my Arduino to control DMX512), I find mostly two types: GPIO / TTL based (which I want to use), like TTL RS485, which mainly has a MAX485 and some ...
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286 views

TTL to RS485 converter faulty outputs

I'm trying to communicate between 2 boards (NodeMCU, arduino mega) over an RS485 hardware setup. This is just for learning to later only the NodeMCU as IoT solution and the mega is simulating any ...
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113 views

Number of bits after stop bit before going to idle state. Is it regulated by a industrial standard?

Does anyone know a number of bits after stop bit before going to idle state. Is there any standard on this matter (e.g. industrial)? Update: So my questions are: What marked areas stand for. What ...
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Cannot use SoftwareSerial and RS485 protocol in the same code

Could someone help me ? I want to make 5 nanos communicating through RS485 protocol with my Arduino Uno master. This part is working great by using the code of http://www.gammon.com.au/forum/?id=...

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