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Questions tagged [rs232]

RS-232 is the electrical standard used on most serial ports. Note that this standard is a +/- 15 volt system and requires a FDMI converter to make it compatible with TTL logic levels.

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Protecting RS-232 from overvoltages

I am using Some arduinos (5V Pro-Mini, but planing to move to actual ATMEGA chip) over a distance of few metres. These are connected using standard Alarm cable (I had problems with Ethernet cable and ...
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1answer
68 views

How to monitor one wire “kind of” protocol

In the current network, there's 1 master device, which gathers data from over 20 devices. Nameplate says the baud rate is 2400. In the bus cable there's one data wire, 12V and GND. A friend of mine ...
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66 views

GSM Modem Transmission Issue

I'm having a problem getting this GSM modem to work with an FPGA (Spartan 3). I've already implemented UART transmission on the FPGA side,the MAX232 to convert TTL->RS232, and 3.3V->5V logic level ...
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107 views

RS485 vs RS232 similarity vs differences

I have used UART RS232 communication between MCUs extensively. Now I need to interface my STM32F407 MCU over RS485 bus with with devices. I have understood few things about RS485 but not-clear about ...
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2answers
52 views

MAX232 vs TRS202EC Line Drivers

I have used MAX232 as UART serial line driver using 5V power supply. Now I have come across TRS202 chip in a circuit. It also run with 5V power supply. Does this chip has some special difference or is ...
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1answer
100 views

RS-232 interface chip problem - why is the voltage level so wrong?

1. What I want to do: I have a PCB with an AVR microcontroller (ATmega16U4) on it. I want the microcontroller to communicate with my computer through an RS-232 cable. 2. What I did: I added an ...
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58 views

What is this weird behaviour I am observing with doing a loopback around MAX3232?

So this is my pretty little circuit that I made. AFAIK all connections are fine and I have tested them using multimeter for any shorts. I was actually testing the circuit by loop back shorting J1's ...
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51 views

Serial communication between raspberry and laptop not giving right values

I want to communicate between a Raspberry Pi 3 model B and a laptop using a USB to RS-232 cable and this RS-232 to 3.3V TTL converter via the serial module in Python: GND is connected to board pin #6 ...
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2answers
408 views

Can a MAX232 IC be used for RS-232C standard?

I have a GT01 Panasonic LCD which it's interface is RS-232C. I have read that the difference between RS-232 and RS-232C is their voltage level which it's ±5 V in RS232C. Can I use a MAX232 IC to ...
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1answer
144 views

Is there a standard describing the UART data frame protocol?

The "U" in "UART" stands for "Universal", but I'm having trouble finding any standard that describes the framing protocol that's used in UART; e.g. the start bit, stop bit, parity options, and baud ...
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93 views

RS232 Data Format “Design” Questions (from non-EE) [closed]

I've been tasked with defining a format for (asynchronous) binary RS232 data sent from one device to another. These are mostly error messages and some engineering data from a custom autopilot device ...
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2answers
303 views

What's the difference between a null modem cable and a gender changer? [closed]

Please ignore this question. It doesn't address the problem I was trying to solve (XY problem) and my edits have been reverted. Because it has answers, I can't delete it. It should be closed as off-...
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minimalist serial port addon to a basic 8052

Currently I have two microcontrollers connected to each other so that I have two serial ports. One to the PC and one to a wireless radio module. Now I'm considering replacing one microcontroller with ...
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1answer
74 views

Does this wiring pattern for a DB9 cable exist as a standard cable?

I have a scientific instrument that uses a DB9 cable to connect to the standard RS232 port on a computer for communication. I've deconstructed one of the cables as I needed to make another one but I ...
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3answers
595 views

Is the ATMEGA328P's serial baud rate quantised?

I'm using an ATMEGA328p, running from its internal oscillator (divided by 8 = 1MHz). I've (roughly) measured the oscillator output, using my Salae logic analyser, as ranging from 960KHz to 1000KHz, ...
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79 views

Design Environmental test chamber RS232 protocol

I have recently acquired an environmental test chamber from Design Environmental. The unit has what appears to be an RS232 interface from which I can get nothing sensible. As you can see, the DB9 ...
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1answer
129 views

What is 8 pin tssop packed component?232/485 ethernet converter

-size = 2.9mmx3.1mm -GND pin = 1,6,7 connected -7.pin 4.7uh connected
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2answers
2k views

Why can't I successfully send messages over RS232?

So the past week I have been working on getting UART messages sent from a STM32F407 and reading it on my laptop through a ugreen RS232 to USB cable using termite. I have used STMCube to generate ...
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2answers
222 views

Purpose of this oscillator (74HCT14-based) on RS-232 to RS-485 converter?

I am reverse engineering an RS-232 to RS-485 converter to understand how it works. I have attached the schematic that I reverse-engineered from the PCB (apologies for the hand-drawn schematic). I've ...
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2answers
92 views

Help figuring out the interface on this bill validator?

I would like to interface this bill validator to a microcontroller (Arduino Mega). The website says it supports RS232,RS485,Optoisolated RS232 and USB interface. The one I have is currently intefaced ...
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3answers
478 views

How to find out whether serial standard is RS232 or TTL when stated as “serial(RS232/TTL)”

I am recently moving from C programming into automation engineering. I have learned about RS232 and TTL standards, and I understand that they are based on the same concept of serial communication, ...
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1answer
82 views

Intel Altera MAX 10 DEV KIT Interface - Can a RS232 6 pin PMOD module by Digilent be used seamlessly with MAX 10 for PC-FPGA UART communication?

I am planning to either purchase a MAX 10 or a DE2-115 dev kit to implement communication via both ethernet and RS-232. DE2-115 has both ports soldered onto the board, but MAX-10 has 2 ethernet ports ...
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3answers
93 views

Unsure how arduino is interpreting RS232 signal

Disclaimer: I am a novice. I have an RS232 connection with an RFID tag reader which I am monitoring via software on a desktop computer as well as an Arduino. The device is configured with 8E1 parity. ...
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175 views

What is the function of diode and capacitor in RS232 shifter circuit?

as shown in the picture, can anyone explain the capacitor and diode in detail? Thank you!
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4k views

What are TX and RX relative to?

I have been working with a device that uses RS232 communication to a PC. There has been some confusion as they have defined their TX and RX pins relative to the device. In their definitions they use ...
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2answers
5k views

What is the difference between RS-232 and RS-232-C?

I know about RS-232. Later, I heard about RS-232-C. Are these two standards the same or not? If not, what are the differences?
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RS-232 signals on Bluetooth modules like HC-06, HM-10, etc

I would like to access any I/O pins of a bluetooth module of the likes of HC-06, HM-10 or their clones from both a Windows PC and/or Android system connected wirelessly to the module. I need Windows ...
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2answers
75 views

Hot switching between RS232 ports

I have a system with two serial devices (Arduino uControllers) connected to a single FTDI (USB-to-Serial) chip through a silicon switch. Each devices works fine on its own. I would like to be able ...
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2answers
94 views

FTD232RL displays gibberish

Hello there i am using dsPIC30F4013 and i have been trying to interface uart with pic. I want to send some data to PC via uart and display it on terminal, but what i get is far from what i expect, to ...
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1answer
174 views

max232 charge pump problem

I have a problem with my MAX232 chip and can't find the solution. The schematic of the chip is in the attachment. The chip is soldered on to a PCB. I've checked all the connections, the supply ...
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0answers
68 views

How to wire RJ12 to db9f modular adaptor?

I have a RJ-12 to DB9f modular adapter. There are 6 wires that come out of the adaptor (White, Black, Red, Green, Yellow Blue) - these, as I gather from pin out diagrams, correspond to the 6 jacks of ...
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1answer
101 views

Which cable for 230.4 Kbps RS-232

I have to communicate between a sensor module and micro-controller board. The sensor module uses UART at 230400 bps. I have used a MAX3227 on sensor module as well as micro-controller board. So, the ...
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1answer
340 views

How to connect STM32 with DAC?

I have to do a project for my Uni, where one of the requirements is to connect DAC (AD5721 - Datasheet) with STM32F405RGT6 (Datasheet - package : LQFP64). This is what I have so far (DAC connected ...
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2answers
61 views

RS232 Bridge cable stopping after some time

Im trying to reverse engineer a very old DOS program that connects with a machine using RS232, for this i setup a typical in the middle connection like this: From Computer A to PC A connection im ...
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1answer
519 views

USB to RS232 without host (slave devices)

I'm trying to get two slave devices (ie no host controller) to communicate. Slave 1: USB with FT232RQ chip Slave 2: DB9 Using standard USB to RS232 converter cables, I cannot get the two devices to ...
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71 views

Why, for RS232 DB25 and DB9 the TX and RX reversed?

Why, for RS232 DB25 and DB9 the TX and RX reversed? For example for a DCE, DB25 connector, TX is on pin 2 and RX on pin 3. However for DCE, DB9 connector, TX is on pin 3 and RX on pin 2. I thought ...
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1answer
1k views

FTDI USB/TTL-serial converter - what are TXD, TXL, RXD and RXL?

I've got a couple of TTL USB/serial converters. I think they're FTDI chips. As well as pins marked TX and RX, there are unpopulated holes marked TXD, TXL, RXD and RXL. I've previously thought that ...
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2answers
607 views

Is it possible to talk with Attiny85 via serial interface?

Alright, I know this question is pretty silly, but I have stumbled upon different posts saying opposing things. So to make a conclusion, does anyone knows for sure if it's possible to send data via ...
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1answer
154 views

Transmitting through IRDA as if its a native serial port. Possible?

I'm currently making a lazertag project that utilizes the standard UART data format for data I/O. Before I go make up another circuit board that connects a photo-transistor that senses a laser beam ...
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1answer
157 views

Can you send RS232 messages to yourself in PuTTY?

Say you use PuTTY serial mode and a USB to RS232 cable. Can you send messages to yourself if you wire the TX of the cable back to its RX, not haphazardly, there's probably a bit more set up detail. I'...
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2answers
185 views

Upon setting up serial UART between two boards I can only monitor send or receive, not both, Why?

I have an atmega389B talking to a SAMD21 chip over UART and am trying to monitor the data sent by the SAMD21 and 389B chip. The baud rate used to be 9600 8N1 and I was able to observe both the sent ...
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1answer
56 views

How can I confirm the correct pinout of a USB <> RS232 null modem cable?

A loopback test with HyperTerminal, or something similar, will confirm the cable itself is working. But I want to know if the pinout configuration is indeed as expected... i.e. That pins 2 and 3 are ...
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1answer
80 views

Why all the other ultrasonic sensors are getting triggered when only one so actually triggered?

I have an ultrasonic sensor, HC SR04, connected to the atmega 8 controller along with an LED for the indication purpose. Let me discribe about my project with some anology. Say I have 20 rooms( ...
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2answers
86 views

RS 232 - 4th pin purpose

I have been using the schematic of MCB1700 Evaluation board in my customized ARM Powered board. I planned to use RS 232 communication on my board. When I go through the schematic, I am stuck with the ...
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4answers
915 views

What will happen if I don't use RS232 driver for UART?

I already read some topics about the difference between UART and RS232, but I still didn't get it. I read that UART is kind of logical interface, and RS232 is physical interface. But I don't ...
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1answer
95 views

JR3 force sensor with digital output (internal electronics)

My employer asked me (I am a software engineer, and sadly I have little experience in fiddling with hardware) to try to couple our JR3 force - torque sensor with a PCI card reader that we managed to ...
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1answer
64 views

Looking to Identify a connector, to engineer a solution using a USB connector

I have been tasked with installing an NCR 76 (7876) Scanner/Scale in my grandfather's store. The device was purchased over mercadolibre.com and was not sent with documentation, but was supplied with ...
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0answers
322 views

RS232 using a MAX3232 chip problems [closed]

I am trying to use RS232 to TTL convertor much like this: https://www.amazon.com/MAX3232-Female-Serial-Converter-Module/dp/B00BXX2OU2 I am not sure if the chip is authentic MAXIM or some knock off. ...
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2answers
332 views

3.5mm to DB9 connector (differences) [closed]

I have 2 different type of connectors of 3.5mm to DB9 that I use to send RS232 commands from device to a screen. The 3.5mm is attached to the device on the serial port and the DB9 to a serial cable ...
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1answer
364 views

Use RS232 - RS422 Converter with Encoder

Problem I am trying to communicate an incremental encoder (TTL/422) with a PC, however, the PC is modern (correct me if I am wrong, It is a Sabertooth Z77) and doesn't have parallel ports... I found ...