Questions tagged [rs485]
EIA RS-485 is a serial communication standard using differential signaling.
635
questions
0
votes
0
answers
15
views
Difference between Echelon TPT/XF and RS485 transceivers
We are going to connect to a LonWorks network and all devices connected to network have TP/XF-78 transceiver. Can anyone describe the difference between the two?
- 173
0
votes
3
answers
70
views
Powering a device from the RS485 lines
I have found multiple RS232 to RS485 converter dongles (from different brands, models, and makes) that do not need external power to operate.
Connect the RS232 DB9 on one side, and three wires for the ...
- 832
1
vote
2
answers
123
views
How to isolate RS485 (A and B) from existing transceiver? Check attached circuit diagram, is it correct?
I have a controller with an RS485 transceiver, specifically the IS8489EIBZ-T, which is not isolated. I want to connect a BMS system to the output of this transceiver. After some research, I found a ...
4
votes
2
answers
222
views
TTL to RS485 converter problems
I have designed a custom PCB that incorporates a circuit for an RS485 to TTL converter. Previously, I successfully used a module (https://protosupplies.com/product/scm-ttl-to-rs-485-interface-module/) ...
- 51
2
votes
0
answers
34
views
rs485/modbus issue
I am trying to enable modbus RTU communication between 2 inverters.
Both are set up with unique IDs, 9600Hz, 1 stop bit, No parity bit.
I can communicate with 1 at a time, as shown below in the ...
- 21
1
vote
1
answer
84
views
USB and RS485 on same lines for ESP32-S3
For an ESP32-S3 based PCB that I am developing, I would like to be able to share 1 connector for two different communication protocols.
USB connection directly to IO19 and IO20 of the ESP32-S3-wroom1
...
0
votes
0
answers
29
views
ATTINY85-20SUR and serial communication
I am trying to use this chip ATtiny85 for serial communication. So my question is, would you recommend using it for serial communication, such as storing names, IDs, data, and last operations? Should ...
- 21
7
votes
3
answers
638
views
Can you connect an RS-485 bus as a loop? (no terminators, cable ends joined)
I'm looking at using RS-485 to connect a bunch of sensors across a lengthy distance (approx 500 metres) however the location of the sensors means it would be suitable for connection as a loop.
By loop ...
- 1,795
3
votes
1
answer
145
views
UART communications using CAN bus differential signalling
I need to interface with a device that talks UART, but with CAN bus signalling. Here's a picture where a tester (which I want to replicate) talked to that device:
While RS485 seems similar, the ...
- 175
3
votes
2
answers
327
views
Help understanding RS485 circuit
Could someone help me understand this circuit? Like what is the purpose of the logic inverter, is it for switching direction automatically? And if so, how is it working?
For example on the TX1 line - ...
- 51
0
votes
2
answers
79
views
RS485 to CAN converter
I want to design where a RS485 Device Sensor reads inputs and the information it reads and sends is converted to CAN (Arduino UNO R4 Minima with CAN built in, or ESP32 with CAN built in)
Is this ...
0
votes
0
answers
51
views
Replacing MAX485ESA IC into a RS485 module but not working
I have been struggling a lot with a MAX485ESA IC I bought from aliexpress. What I want to do is replace the component from a rs485 module. For some reason they don´t work and I was wondering if anyone ...
- 11
2
votes
3
answers
267
views
How to find out if RS485 interface has termination
We have a battery with built-in BMS and I am preparing a PCB that is supposed to talk to it. I need to decide whether I put 120 ohm standard end termination or 60 Ohm for 20cm short "bus".
...
- 12.9k
1
vote
1
answer
181
views
Noise during RS-485 operation
I have a switching step-down power supply SCM1301A, from which the entire circuit is powered, namely the microcontroller, op-amp, RS-485. I digitize the signal coming from the microwave module, having ...
- 41
0
votes
2
answers
115
views
Why are there two wires connected to each terminal of the RS485 port in energy meters
I want to connect the energy meters of our clients to a gateway so that the gateway can communicate with the meters using Modbus. I have visited several electrical rooms that have gateways installed ...
- 335
10
votes
7
answers
2k
views
Puzzle how isolated RS-485 (ADM2582) sends signal without signal ground
Galvanically isolated RS-485 surely needs a signal ground, which leaves me puzzled about the following circuit -- which apparently sends the RS-485 signal correctly without the isolated grounds being ...
- 15k
4
votes
4
answers
399
views
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 ...
- 45
1
vote
1
answer
67
views
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 ...
1
vote
2
answers
157
views
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 ...
- 7,697
0
votes
1
answer
35
views
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 ...
1
vote
1
answer
109
views
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)?
- 11
1
vote
2
answers
75
views
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 ...
- 828
0
votes
1
answer
151
views
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-...
2
votes
1
answer
155
views
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 ...
- 399
0
votes
1
answer
47
views
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 ...
0
votes
3
answers
270
views
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 ...
- 22.8k
0
votes
1
answer
166
views
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 ...
- 1
0
votes
2
answers
66
views
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 ...
- 5
0
votes
0
answers
140
views
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 ...
- 423
0
votes
0
answers
121
views
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 ...
0
votes
2
answers
122
views
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 ...
- 249
2
votes
2
answers
157
views
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 ...
- 53
2
votes
3
answers
1k
views
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 ...
- 828
1
vote
1
answer
260
views
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 ...
- 25
1
vote
1
answer
328
views
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 ...
- 25
-1
votes
1
answer
509
views
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 ...
0
votes
0
answers
134
views
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.
...
- 1
0
votes
1
answer
136
views
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 ...
- 1,369
0
votes
2
answers
162
views
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 ...
- 3
0
votes
1
answer
527
views
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 ...
1
vote
0
answers
85
views
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 ...
- 111
0
votes
1
answer
40
views
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 ...
- 2,391
0
votes
0
answers
97
views
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 ...
2
votes
1
answer
177
views
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 ...
- 756
2
votes
2
answers
190
views
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 ...
- 173
0
votes
0
answers
131
views
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 ...
- 101
4
votes
2
answers
851
views
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 ...
- 2,391
3
votes
2
answers
123
views
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" ...
- 33
0
votes
0
answers
238
views
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 ...
- 1
0
votes
2
answers
415
views
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 ...
- 3