Questions tagged [rs485]
EIA RS-485 is a serial communication standard using differential signaling.
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ESD protection on an isolated circuit
I'm currently working on an RS485 DMX circuit and am thinking about proper protective measures.
I've oriented myself on this question. I understand that galvanic isolation does not equal ESD ...
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RS485 Node/Cable Testing/Simulation
I am designing a system using RS485. There will be >100 nodes on a bus, each with input and output connectors, separated by ~1m.
In order to determine the signal quality at various speeds, I would ...
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RS485 Protocol Reverse Engineering & Replay Challenges
I'm trying to reverse engineer the RS485 protocol used by my home heater/AC.
This protocol handles communications between the wired remote control (WRC)/thermostat and the main heater/ac indoor unit (...
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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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RFI protection for a stepper motor controller
I'm building a remote tuning device for a magnetic loop antenna. It will use a stepper motor to turn the shaft on the mag loop's variable capacitor. The electronics will consist primarily of a ...
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Implications of using a 2C-#18 twisted shield pair nec type cmr cable for RS-485
The cable will be passing modbus and another equal cable will be used for loadshare. The total cable distance will be about 100ft. Its catalog number E2032S.
I notice other threads related to CAT5, ...
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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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Which instructions do I use to be able to use UART directly on my STM32F107 microcontroller?
I've tried to figure this out on my own but after almost a week I'm still at more or less the same place where I started. So, I have an STM32F107 microcontroller on a board, which is linked to another ...
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Isolated RS485 without specialized IC
I'm looking for replacement for ADM2587E.
This is ADM2587E:
Can I just use cheap, not isolated RS485 transceiver like MAX485 connected to microcontroller TX, RX, DE/_RE via optocouplers and power it ...
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Choose between Profibus PA and DP
I currently try to understand a new technology: Profibus, until now I worked with HART, with which I also had some struggle in the begging but now it's clear. I try to understand why in a factory is ...
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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 ...
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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 ...
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Put RS485 microcontroller and transceiver to sleep and wake it up on incoming data
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 the MCU into sleep mode and I want to wake the MCU up, when ...
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RS485 ground noise problem
I'm using the USB FTDI dongle to convert USB to RS485, half duplex, 3 wires (A+, B-, GND) with 115200 baud rate.
I'm working with controller of NXP (K64) and I'm experiencing random tx enables on the ...
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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 ...
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Cable shielding groundloop
I am trying to connect a encoder to a motor controller which runs very close to the motor that it controls (30+ amps). Due to the risk of high EMI of the motor inducing on the encoder signals, we send ...
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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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RS-485 4-wire to 2-wire converter
I'm looking for a way to be able to electrically switch between 4-wire and 2-wire RS-485. Up until now I have used jumper connections to establish both communication ways with one circuit. But I would ...
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Serial circuit protection design
I've been researching RS485 hotplug protection for a while and come up with the following solution. The reason is that I burned two custom Arduinos, after further investigation it turned out the GND ...
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What are the correct signal ground connections in an RS485 system with a shared ground on motor drivers?
I'm in the process of designing a motion control system using RS485 and whilst we've generally made things work in the past with a more trial and error approach, in the interest of doing things right ...
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Connecting 12 V RS485 appliance (soil sensor) to USB 5 V RS485 adaptor
I have a 12 V RS485 appliance that measures some soil resistance etc. It is a 7-in-one soil sensor, the 12 V version of the 5 V version shown in the link.
I could not find a 12 V USB to RS485 adaptor ...
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Flashing an ATMega microcontroller using a USB Connection
I'm trying to get into embedded system design and have been hung up on what hardware is required to use a USB connection to communicate with the microcontroller (and therefore, flash it). Here's what ...
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Modbus over RS485 - no response from device
I am trying to connect to Epever Tracer AN Solar Charge controller from ESP32 using below Max485 module but I can't get any repsonse from device.
I was trying to use exactly the same setup mentioned ...
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Fault Protected RS485 circuit
I am designing a product for use in the industry and it needs to include a fault protected RS485 interface.
In the industry the most normal voltage for the power supplies in the machinery is 24V, but ...
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Atmega328 and max485 schematic problem
i'm making atmega328 and max485esa in one pcb.
first build using an external 5v dc source and without any problems. the code works fine, the ws2812 led on the receiver module can light up.
the second ...
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How to create an RS485-compatible line driver with an adjustable slew rate?
I need to make an RS485 compatible line driver, capable of 12Mbit/s with fast slew rate, but with the capability to reduce the slew rate to about 50ns rise/fall time when operating at lower bitrates.
...
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Need Help Connecting Arduino to PC via RS485 with Max485 breakout board
I am currently attempting to connect an arduino to a PC via the RS485 communication protocol using a max485 to convert the RS485 to serial. It does not however appear to be receiving any data at all. ...
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How to test for PCB ground being pulled up to 2V when connected to RS485
I am currently trying to find an easy way test to diagnose a problem on some of our PCBs where the ground of the PCB is being pulled up to 2V's.
The Board
Simple modular RS485 sensor board. The main ...
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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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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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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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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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MAX487 can transmit but won't receive
I am trying to use a MAX487 chip to convert a regular UART signal to half-duplex RS485 signal and vice versa. I am using Atmega328PB as my micro controller. My circuit has no problem with transmission,...
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RS-485 device to RS-232 adapter MUXing not working as expected
I have a RS-485 device that returns serial ASCII constantly. As the device might near very high voltage or electromagnetic areas, I need to ensure the RS-485 to RS-232 adapters I've been supplied with ...
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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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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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SPI with differential line drivers, and star configuration problem
Folks I am helping to design a circuit for a group that uses the odrive motor driver board. The odrive drives two brushless motors and the MCU uses SPI to connect to motor encoders. People using the ...
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Electronically verify whether a cable is connected to an RJ45 connector
Background:
I have a device that interfaces with a motor controller over RS-485 via an RJ45 socket. Currently, the port is a standard 4x2 RJ45 connector with the RS-485 using pins 2 and 7.
Currently ...
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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 ...
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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 ...
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Problem with Pyserial read time
I'm building a RS485 network with rpi3 as master and a bunch of c51 mcu as slaves. After sending an address, the master waits for the slave to respond and then starts to send data. I'm using Pyserial ...
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RS485 transmission errors
I am trying to get two Atmega328ps to talk to each other over RS485 with MAX485 as transceiver. Below is the scope trace of D+ and D-.
Yellow : 485A line,
Cyan : 485B line,
Blue: A - B (...
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For wrong termination resistor uses
Over 485-interface slaves are connected as multi drop, physically daisy chain.
Those have built-in termination resistor, and the value is 120 ohm and no select switch for termination on/off.
So it ...
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Using same DB9 port for RS232 and RS485 (selectable) - looking for IC
Do any of you know of any transceiver ICs that can switch between RS232 and full or half duplex RS485? I'd like to be able to select which type of communication is used with either a jumper or input ...
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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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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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Modbus ASCII messages delimiter
I need to implement Modbus messages reception over UART. For RTU it's easy because UART on my uC has configurable idle receive line detection. However, for ASCII the task is tricky - the delimiter is ...
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Modbus RTU on ESP8266 to control VFD
Hoping to get some help on setting up a NodeMCU (esp8266) with this 1 arduino library to control a Variable Frequency Drive (VFD).
I'm afraid to say that I almost need help from square one, as I'm ...
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Why does this 7-in-1 soil sensor print mixed values?
I'm working with a JXCT-IoT seven parameter soil sensor.
I did tests to print each parameter and it prints the correct value but when I put in all the code, the values are mixed. For example, the ...
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Overvoltage protection for RS485 from DC-DC voltage
I am making a circuit to protect RS485 against 24V and 32V DC over-voltage. Note that my power supply is 12V. I've done my research and found solutions, but I can't fake it.
More specification ,my ...
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