Questions tagged [rs485]
EIA RS-485 is a serial communication standard using differential signaling.
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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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36 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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52 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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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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How to count number of bytes appearing in the Arduino serial? [migrated]
I need to count the number of bytes appearing in the serial (UART bus) bus, how to count bytes in Arduino with Arduino Serial functions? is this possible?
Application -
RS485 communication with ...
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1answer
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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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1answer
31 views
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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48 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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1answer
65 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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47 views
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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34 views
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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2answers
58 views
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
42 views
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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2answers
31 views
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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3answers
91 views
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
58 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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31 views
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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1answer
103 views
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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1answer
76 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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1answer
66 views
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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1answer
179 views
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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3answers
61 views
Protocol with twisted pair for multiple switch control in a tree topology?
For an irrigation system, I'm interested in simple switches. My requirements:
Communication over copper wires, e.g. a twisted pair of cables
Nodes(switches) can be set in a tree topology, all sharing ...
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1answer
84 views
TVS diode for RS485
I'm studying the ISO1500 for an RS485 application. In particular, I'm looking for a TVS diode for bus protection. I've found that a common TVS diode used for RS-485 applications is the SM712 (like ...
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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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Could Cat5e be used for RS485 [duplicate]
I'm working on a project that will be using RS485 to communicate between a bunch of modules and a master controller. Low baud rate, 9600, but a decent distance, like a couple of hundred feet. I'm ...
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1answer
101 views
FT4232H: Configuring RI# as TXDEN Using FTProg
I am developing a device based around two FTDI FT4232H quad USB-to-Serial converters plugged into a Texas Instruments TUSB2046 USB hub controller. The serial outputs of each FT4232H channel goes to a ...
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1answer
129 views
ADM2483 or MAX485 Design: Modbus RS485 RTU bus in harsh environment
I'm currently out of ideas, i have a simple Wigoneer RS485 TTL interface (Sch link here) with MAX485 wired to my ESP32 based board, in my lab everything works like a charm with 1300 meters of CAT6 UTP ...
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1answer
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Re : RS422 module from Aliexpress
Was planning to work on some long distance communications with RS485 / RS422 and I saw one of these boards on Aliexpress,Amazon etc..
Does anyone know what all those passive components could be?
Would ...
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1answer
49 views
Long Range (100m) USB(PC) to USB (microController USB module) Communication
I have a system that communicates between PIC32MX250F256D (USB module) and PC via USB (2 meters apart). And I need to increase the range of this communication to 100 meters. Due to typical 5m limit of ...
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1answer
75 views
Sniffing an RS-485 communication
I am trying to sniff a serial communication between two devices. One of them sends a command (6 bytes + 2 bytes CRC),
the other one responds (4 bytes + 2 bytes CRC). My computer monitors the exchange ...
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2answers
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Effective differences between MAX485EESA+T and MAX485ESA+T?
Is anyone able to explain to me the effective difference between the MAX485EESA+T and the MAX485ESA+T?
The datasheet points out that is more tolerant of ESD discharge up to 15kV, nothing more.
Can ...
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1answer
19 views
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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1answer
47 views
How to increase data through put of RS485 RTU?
I am using 20 sensor nodes, each has mpu9250 i2c, Arduino atmega328 MCU 8MHz and max485 chip in it,
each slave has a unique id program.
I have Arduino due as Modbus master with max485 chip,
I hope ...
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3answers
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Why single ended signal line is not immune to noise in RS232?
In single ended signal line the measurement is the difference between the signal and the ground. Isn't this way of calculation make it differential?
Almost all the resource I have read says that ...
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2answers
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Wrong output using SN75HVD10 (RS485)
Designing a modbus master using a STM32F030CCT6 and a SN75HVD10 (3.3V).
This is the schematic
When i send the following message from the UART:
01 03 00 00 00 06 c5 c8
I see the following scopes (...
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1answer
92 views
Using CANbus cable for RS-485
I have a question regarding an application with a Modbus RTU network.
I would like to know if it's possible to use a CANbus cable instead of an RS-485 cable? Here is a picture of the cable:
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1answer
59 views
Is it possibile to use a CAN transceiver to send RS485 data?
Looking at the signal ranges I'm not sure if I can use a CAN transceiver (not controller!) to send data to a single RS485 device.
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1answer
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Is there some kind of standard of modbus input register?
As the title said,
based on your experience, is there a such thing?
If no, which are the most commonly used?
for example in a sensor, the input registers as follows:
...
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1answer
98 views
USB to RS485: Can I connect A to Common Ground?
I bought a very cheap USB to RS485 dongle to connect to an experimental board of my own.
Specifications (may differ from the one I used but externally similar):
- Any baud rate from 1200 bps to 115 ...
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0answers
373 views
RS485 Pull-up, Pull-down and single termination resistor
Currently I use for Modbus RTU via RS485 with a shielded cable length of about 5 meters and a bitrate of 19.200 bit/s. Wired are 680 Ohm pull-up (A->+5V) and pull-down (B->GND) resistors near to the ...
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1answer
58 views
Can power supply be chained?
In my current project, I need to communicate and supply current to 4 sensor PCBs ("S1", "S2", "S3" and "S4") from a master PCB ("M1"). I will use RS-485 to communicate between PCBs, meaning I can ...
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36 views
Rs485 all nodes not communicating
I am Using a gateway etor-4 to convert Rs485 to ethernet and then provide data to Modicon 580 cpu.My slaves are tm221 controllers which are 22 in number.The problem is I can get only 5 nodes data ...
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2answers
294 views
Use half-duplex or full-duplex RS-485?
I have a master microcontroller that can control 4 slave microcontrollers. Each slave microcontroller is connected to 3 sensors.
The master microcontroller asks to retrieve the value of a specific ...
