EIA RS-485 is a serial communication standard using differential signaling.
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19 views
How to Control SM1 Inverter Drive Frequency with Arduino?
I am back at trying to control the frequency of an SM1 AC inverter drive due to the fact that I never got it going the first time. However, this time I would like to use an Arduino. The manual for the ...
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1answer
36 views
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0answers
60 views
Faulty RS-485 device has irregular effect on neighboring devices in bus setup
I am trying to understand the mystery of how one faulty RS-485 transceiver, in a network bus with several devices, seems to have very irregular influence on its own and its neighbors transmission ...
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3answers
188 views
Serial bus Raspberry Pi to multiple AVRs
Background: I'm trying to replace the electronics for a ice hockey scoreboard. The old electronics had the following issues:
It stop working. I have since discovered that a couple of diodes and ...
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3answers
100 views
Any good way to automatically enable an RS-485 transmitter in hardware?
Does anyone know of a good circuit that would automatically enable the transmit on an RS-485 driver when characters are transmitted? In our designs we currently use RTS to drive the driver transmit ...
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2answers
117 views
How to de-couple DMX512 with opto-isolators?
I'd like to build a DMX512 device.
The problem I have is how to decouple the device from the bus. I decided to use opto-isolators, but how should I wire the diode part of the isolator?
Since I need ...
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1answer
62 views
J1708 Half Duplex Collision Detection
SAE J1708 is basically an RS485 hardware interface without the typical 120 ohm termination resistors. In typical applications, a half-duplex RS485 transceiver chip is used to connect to the bus.
In ...
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1answer
153 views
Pull-down resistor with ADM485
I have ADM485 already mounted and an output of some device, buffered by CD4050BM. For the circuit to be safe for the RS485 bus, the ADM transiver initially should either be in Z-state or read-state. ...
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2answers
340 views
No response from device when using rs485
I've been stuck on this issue for quite some time. I am trying to use an arduino to communicate with another device using RS485. The problem is that I can see the data being sent but, the device does ...
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1answer
185 views
Unable to communicate with a deice over rs485 [duplicate]
Possible Duplicate:
No response from device when using rs485
I've been stuck on this issue for quite some time. I am trying to use an arduino to communicate with another device using RS485. ...
3
votes
1answer
215 views
What serial signalling format is this? (RS-485?)
This is a mystery signaling standard that I'm trying to sort out. It looks more or less like RS-485 to me, but I don't recognize the long looking start bit, and the "idle" state of the line looks a ...
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1answer
184 views
DMX512 Remote controlled LED
I'm having a problem with this circuit. I am trying to get an LED wash light circuit to be remote controlled via DMX512. The problem is, after I designed the circuit for the RS485 (which will deliver ...
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1answer
2k views
Arduino as modbus master with MAX485 doesn't get any response
I'm having some troubles trying to query a modbus slave with an Arduino through RS485.
I've already succeeded in querying a software modbus slave running on my PC through the USB/COM port using the ...
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3answers
672 views
Different behavior of FTDI USB RS485 on different computers
I use a FTDI USB-RS485 adapter cable to connect a RS-485 device to a computer.
The communication is fairly simple, the computer sends periodic requests, the device answers them.
On one computer ...
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0answers
20 views
Framing error on Rx line in rs485 to ethernet converter [duplicate]
Possible Duplicate:
Framing error on Rx line in rs485 to ethernet converter
I have a device connected to MOXA nPort 5150 via 4-wire rs-485 cable. Termination resistor inside the converter ...
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1answer
187 views
Framing error on Rx line in rs485 to ethernet converter
I have a device connected to MOXA nPort 5150 via 4-wire rs-485 cable. Termination resistor inside the converter was set to 1 kΩ (another option was 150 kΩ, which didn't work at all - I got framing ...
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2answers
153 views
RS-232 and RS-485 software configurability?
I would like to connect a anemometer(RS-485, DB9) to the PC. The PC has a serial port with DB9 connector. I couldn't find the specification of the serial port. Is that RS-232 standard or RS-485? Most ...
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1answer
91 views
Why does it hase a power supply for the rs232 to rs422?
We have a anemometer with RS422/485 communication, and we would like to connect to the PC, but we have only RS232 so I would like to purchase a converter, but some converter has an external power ...
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1answer
109 views
Transmitting pulses via RS485
I will have an IR led / photo transistor based reflective sensor, measuring rotation speed of a wheel, producing pulses using a comparator with hysteresis. The pulses will be counted by ...
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1answer
288 views
RS485 Cable Lengths and Reflections
In our lab we have setup a RS485 network with short cables and the network is working fine. I know that terminating resistors are required, especially with longer cables lengths due to reflections on ...
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1answer
295 views
RS485 how to tell if HXPS-2108F Prolific is working
newbie at electronics (not PC's or software) - my first project is to connect the PC up to a Solar Power Inverter to datalog. Aurora inverter.. great wiki here ...
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2answers
3k views
Is CAT5 cable good enough for RS-485 vs “true” RS-485 cable
I have a serial comms project coming up. A number of boards with RS-485 interfaces need to communicate. Date rate is 57600bps and cable length will be less than a few hundred feet.
Will shielded ...
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1answer
249 views
Unused twisted pair termination with RS-485 on 8P8C
For my digital electronics project, I'm making a device which will among other things have RS-485 communication.
From what I've seen, the recommended cable type for RS-485 is twisted pair, and one of ...
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1answer
165 views
Implications of using 145 ohm cable for RS-485
My current workplace has made up some custom cables that have conductors for DC power and conductors for for RS-485 communications in the same bundle. My predecessor apparently had the cables ...
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1answer
85 views
RS485: What is the difference between RO and D_OUT?
I have an RS485 transceiver (datasheet here). Page 8 explains the various pins. I do not appreciate why there are two output pins, namely D_OUT (pin A1) and RO (pin A6).
The first is a "General ...
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2answers
439 views
At what cable lengths are termination resistors required for RS-485 networks?
I've noticed my experiments in the lab with RS-485 work fine with fairly short cables, but termination resistors are needed for true installations. Is their presence or absence a function of the ...
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3answers
282 views
Ideal serial communications test?
I'm working on a new customized motor controller system I've inherited. The system has a heirarchy of controllers - a PC communicates to an RS-485 serial bus of one level of controllers, and each one ...
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1answer
317 views
Hijack/observe RS485 communication data by wire tapping?
I have some Computer -> LED Matrix Screens system like this diagram:
...
5
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2answers
586 views
Sensor Polling via USB-RS485 Serial Interface stuck at 16ms, even though it should be faster
I have a setup, connecting a Razor IMU sensor board, with a RS-485 Breakout board, to a USB-RS485 Serial Interface via USB-cable into my laptop. I run a software on the laptop (Max/MSP) that sends out ...
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1answer
291 views
RS485 Communication
I need resourceful information's on how to implement the serial protocol via an RS485 interface. As regards to my area of application, I simple want to communicate with my micro-controller via an ...
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2answers
970 views
Automatic RTS control for RS-232 to RS-485 converters
Okay, so I got my prototype RS-485 circuit working. Now, I've connected it to my PC through RS-232 as I want to make the PC as the master. However, when I connect to the circuit using Hyperterminal, ...
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1answer
427 views
Signal overshoot and undershoot on RS-485 bus
I'm testing an RS-485 comms network that is having occasional problems. Looking at the waveforms on the scope it looks like fairly bad overshoot and undershoot of the voltage levels at signal edges. ...
2
votes
1answer
482 views
Using Zener diode for circuit protection on RS-485 network
I'm examining an RS-485 driver circuit that uses what look like Zener diodes between D+ and gnd and D- and gnd. Anode is connected to gnd, cathode to the D+ or D-. So in this arrangement the idea is ...
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votes
3answers
464 views
RS-485 over many 1000s ft, ground wire and termination always needed?
I've only ever used RS-485 over short connections before. I may have a project coming up where the cables will run several 1000 ft. My questions are:
Is the gnd wire needed?
Should the shield in ...
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vote
3answers
297 views
Connecting LED to RO pin of RS485 Transceiver
I am using this RS485 transceiver in a circuit of mine and I'd like to place a tiny 0805 LED in series with a 1k resistor coming off of the RO (receiving) pin. I'm hoping this would result in ...
2
votes
4answers
587 views
RS232 and RS485 over same pins
I have 2 pins and primary function should be A/B RS485, but is possible that I also put RS232 (Rx/Tx) chip on same bus and then control which one I want to use from microcontroller.
I was thinking ...
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2answers
256 views
On Board Unit communication via RS485
I've heard of On Board Units (OBU) can communicate via RS485. My question is, how?
For example, I would like to ask the state of some runtime variables from the OBU (what doors are open?, etc.) Or ...
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2answers
319 views
Determine transmit and receive latency of a USB to EIA-485 converter
How could I determine the latency involved with transmitting data on a USB to EIA-485 converter?
The converter is a B&B Electronics USOPTL4 using the FTDI chip, and I know that there is a ...
3
votes
2answers
262 views
Parasitic power and an LTC490 as DMX (RS485) bus repeater
I'm in the process of building a DMX bus repeater for a light control installation using the LTC490 bus driver in this configuration:
Now, this works well when using an external power supply (5V ...
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2answers
309 views
Looking for TCP/IP Ethernet <-> RS-485, Half Duplex Device
We are currently using the Wiz108SR device and need to provide this as a consumer ready component with a power supply. We would rather not build and package the powersupply but instead purchase ...
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3answers
2k views
RS485 noise problems: signal ground / common ground / isolation?
I'm experiencing a lot of noise in an RS485 network I've put together using ST485 chips. The cable lengths are very short (<1m total cable length), I'm properly biasing the A and B signals and I've ...
2
votes
7answers
746 views
Communicating between PICs over 30 feet
I have a PIC24F based device that normally connects to a PC via USB. The device can be controlled through PC software this way. I want to add an optional hand control box that can also be plugged into ...
4
votes
3answers
2k views
MAX485 half duplex Atmega communication problem
I want two atmega32s to communicate over a range of 1000ft, so I decided to use a serial wire for it. I know rs232 is not a good way to communicate over this large range, so I decided to use RS485 ...
5
votes
4answers
402 views
Does anyone have any sample code or suggestions to help me to interface my 100 pin uc3a1512to a device via RS-485?
I am attempting to connect and control a device which only accepts RS-485 input. I wish to communicate to this device via my existing UC3A1512. Does anyone have any existing source code or examples ...
4
votes
4answers
531 views
How to use Arduino board to automate testing
ok here goes,
Iam trying to build a device to test nurse call room controllers, these are basically 8 port boards with rs485 linking (have software for this,
what i need to do is test these, to do ...
4
votes
7answers
534 views
Should I consider using RS-485 for my next project
I am planning on an automation project that will be using several different sensors including but not limited to: Temperature, Barometric Pressure, Air flow, Humidity, etc.
As I was talking with ...
