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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Serial2.write not working on ESP32

well I using topway brand HMI display it is very easy to use with Arduino nano or UNO with rs232 converter. this my converter: . for example this code is writing "63" number on display. it ...
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Raspberry PI4 and RS232 adapter cable: how to send serial commands

I would like to use a Raspberry Pi4 to control a syringe pump [(see datasheet here and in particular the quick start manual on page1)][1] The connector cables I used are RJ11 from the Pump to RS232 (...
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How do I exit (Microchip Pic18fxxxx rs232 BTFSS PIR1,RCIF) Loop when no data is present (Assembly Mplab Mpasm)

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Why is my serial connection transmitting slightly incorrect characters?

I have four configurations I'm testing, and one of those configurations is showing symptoms of incorrect transmission in one direction only (from my laptop terminal to the server). Direct connection ...
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MAX232 IC does not convert to and form RS232 levels

I made a simple circuit to read data from RS232 lines and print data on different RS232 lines. This is the IC I am using: MAX3232EIDWG4. The IC fails to convert the CMOS to RS232 level logic. I am ...
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6 votes
3 answers
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Who decides the timing in the async serial communication based on UART + RS232?

According to here, UART is a hardware device that implement the asynchronous serial communication protocol. And according to here, RS-232 defines the electrical characteristics and timing of signals, ...
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How are the bits transmitted over the wire?

This should be a basic but fundamental question. Suppose I have a source and destination communicating over a wire. Source wants to send bit stream 01101 to ...
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3 votes
4 answers
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RS-232 Crossover, and Protection against shorting two TXD lines

I'm in the process of designing a USB to RS-232 converter for communication with some existing boards, and I ran into two problems. First Question I need a way to programmatically reverse the TXD and ...
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RS-485 communication with slave microcontrollers driving addressable LEDs?

I am trying to figure out how to achieve the master-slave configuration shown below. The aim is to individually address an array of 150mA LEDs, driven by the IS31FL3265A PWM driver. For this specific ...
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Arduino NANO heating issue

I am trying use a HMI display with arduino NANO. I am powering arduino and hmi display ( topway 5 inch smart display ) with 9 volt adaptor. everyting works fine. but if I plugin the Tx, Rx pins which ...
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RS-232 returning question marks when reading serial port

I have a question about receiving responses from a machine using PySerial's read method. I am new to this forum as a chemistry student with minimal experience with ...
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D2XX library continuous reading outputs one byte garbage

** [SOLVED] ** I am trying to utilize the D2XX library for continuous reading of whatever the MCU is sending, and printing it on console window. My MCU is atmega328p, which outputs UART, and the ...
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force output on a MAX3232 RS-232 transceiver

I need to probe the output RX (DOUT1/2) nets (connected to one MCU's UART) of a MAX3232 RS232 transceiver, for this I'll use the PCB test points, but I'd also like to "force" logic levels on ...
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Why are *actual* RS232 transceivers RX thresholds so narrow?

I'm having horrible communication issues with an RS232 line. It's near a fat load (not good) and it's a printer (so the comm errors are literally visible). After investigation I actually detected the ...
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3 answers
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Connecting a GPS to computer: Jackson Lab LC_XO serial TTL to RS232 port on computer motherboard

I am trying to hook up my Jackson Labs' LC_XO GPS disciplined oscillator (GPSDO) to my computer motherboard COM/serial port so I can talk to it and for it to send back NMEA messages. Basically, I am ...
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How to connect RS232 level shifter?

I'm trying to use this: https://www.sparkfun.com/products/449 to connect my RPi to my computer via a USB to serial device. (And eventually connect the RPi to other legacy serial devices) My questions: ...
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Why does the MAX3232 have two inputs and two outputs?

I am trying to make a PCB for TTL to RS232 converter. I am using the MAX3232. It looks 10-11, 14-7, 13-8 and 12-9 are the same. I see some diagrams where people only use one of them. For example,in ...
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Maxim MAX3232 chip used as an interface with itself?

I am trying to use a MAX3232ECPE chip to communicate between two ESP32 Feather boards, just as practice with RS-232 conversion before I move on to communicating with an actual RS-232 device. (This is ...
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How to Troubleshoot a Garmin GPS 16x HSV?

I'm trying to get one of these guys talking through a rs-232 serial port: https://support.garmin.com/en-US/?partNumber=010-00258-62&tab=manuals There you can download the manual which has all of ...
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Converting RS-232 to I2C?

I have hardware that communicates using 3-wire RS-232, and I want to communicate with it using I2C. Another post here talks about wrapping I2C in serial or vice versa. I am thinking about using an MCU ...
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How to calculate current value for DOUT and RIN pin in MAX3221E texas IC?

Hi Im going to use ferrite bead in the Dout and Rin pin in MAX3221E IC of Texas. How to determine current rating of the pins , thereby i can choose the current rating of ferrite bead??
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How we select LC filter for MAX3221?

I have seen a schematic where they used MAX3221IPWRG4 (Texas Instruments), RS232 Driver and Receiver. There they have used LC filter of inductor value 0.68uH and capacitor value of 680pF, but in ...
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2 votes
2 answers
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Need to create a circuit for a Man in the Middle Attack [closed]

The title sounds worse than it really is :) I have a printer which is connected to a host, the host uses proprietary hardware to send data to the printer. The issue is the host's date is limited to ...
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2 answers
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2 USB - RS232 adapters both work correctly but voltages significantly out of spec? I'm confused

I have 2 different USB to RS232 adapters; One is a high quality Edgeport adapter and the second is a cheap PL2303 - but both devices work correctly when attached to equipment. The adapters are setup ...
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Issue at programming the power supply via RS232 interface

I’m trying to program DC power supply which I recently bought via RS232 interface. When I try to send commands, I always get '0' value as a return no matter which command I sent. I’m hoping someone to ...
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Help with a RS232 (+-12 Volts) to USB converter [closed]

I have a device I want to communicate to with the following signals: This is a programmable power supply, an IPS-405. I have determined from the image above, which is all that is available in the ...
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Relay controller without the relays? [closed]

I need a way to turn off/on about 20 relays or FETs using RS-232 codes. (I do not want to program a generic microcontroller, I want a dedicated device that is designed to do switching only.) I notice ...
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5 answers
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Control a large number of switches with RS232 via discrete logic

I am working on a device that requires controlling a large number of switches by RS-232. The designer wants to use a microcontroller. So in that scenario, a code is sent via RS-232 to the ...
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Doubts about Max232 IC chip

I have a Max 202 Ic and Max 232 Ic I currently want to make a USB to RS232 Serial Db9 converter i have the db9 male port, a max 232 and max 202 , usb female port and bunch of other passive components ....
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5 votes
4 answers
3k views

Can I connect two microcontrollers via RS232 separated by a distance of 3.5 inches? Both are on two separate PCBs

This design has two PCBs, each with a microcontroller. One can be said to be main and the other is a possible expansion if the user wishes to use it. The microcontrollers will communicate via RS232 (...
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4 votes
6 answers
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Is Ethernet synchronous or asynchronous serial?

I already tried googling but I cannot find an exact answer. Some say it is synchronous, some say asynchronous. For example, see these links: https://www.quora.com/Is-Ethernet-synchronous-or-...
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2 answers
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What was the communication protocol used on board the Apollo moon lander?

It seems that the development of TTL was contemporary ~1961 the maiden moon landing of the Apollo vehicle, while the development of one of the oldest digital signalling standards RS232 using the UART ...
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troubles getting serial port tv to work

i recently posted a question, but didn't had an answer (my fault :) ). my question wasn't straight-forward and clear. so my final goal is to communicate between nodered (raspberry-pi) and my lg tv. I'...
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Why don't LG RS232 commands work when the TV is on (only responds when off)?

I'm writing a new question after stumbling across this question which appeared to have similar symptoms: LG RS232 Commands partially working. As the other question noted, the power on command ...
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Teraterm to show hex data [closed]

I am getting UART data from micro-controller to PC. Micro-controller sends data in hex(eg.0x1B) format which can range from 0x00 to 0xFF. I want teraterm to display the received data in hex format. Is ...
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Running Multiple 12V Sensors to RoboRIO

We run anywhere from 4-10 sensors from Banner Engineering (Photoelectric and RFID). They use 12V power and have a PNP output. Each sensor is 4 wires (12V, GND, NO, NC). Our goal is that we can run the ...
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1 vote
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Connecting RS232 GPS Board to Raspberry Pi

I purchased a NEO-6M GPS board to connect to my Raspberry Pi, and when I bought it I didn't realize that it was meant for RS-232 communication instead of UART TTL (which I believe is what the ...
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1 answer
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Send Serial data and Ethernet data both over WiFi [closed]

we have to make an upgrade in the system which currently uses serial communication using RS 232 which is wired(obviously). send video data via ethernet. So now we want to add send both the data over ...
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1 answer
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Building a RS232 switch [closed]

I have an RS232 input and 2 audio lines that I want to switch to either computer A or computer B depending on the state of a physical toggle switch. Can anyone point me in the right direction of what ...
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Understanding jtag between microcontroller and devices

I am trying to understand how a micro-controller (in this case a C2000 from TI) communicates with other devices via jtag. The device here is a FT2232 (a jtag to usb converter). According to the figure,...
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How to interface a thermal printer to an Arduino

I've a thermal printer which has TTL, RS232 & a four pin interface. I want to connect it to an Arduino and take printouts with it. It has the following pinouts: RS232 & TTL GND TXD RXD DSR ...
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2 answers
51 views

Using USB-RS232 adaptor for USB-TTL connection? [closed]

Seems there are plenty of questions relating going in the opposite direction, but I couldn't find anything that really told me if I could do this.. I have one of these https://uk.rs-online.com/web/p/...
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RS232/TTL converter with Arduino not recognized as serial device

My goal is a very basic one: I want to communicate from my microcontroller to my PC/phone via RS232. I bought a TTL/RS232 converter like this. And since my PC does not have a RS232 port I am using a ...
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MAX233 problem with receiving data

I need to make serial connection between regular PCs and a 3.3v TTL device, I using the Maxim 233 which has internal capacitors. I have the PCs incoming TD connected to R1_IN and RD T1_OUT. The ground ...
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2 answers
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Is it possible to carry RS232 signals over a USB cable?

Is it possible to carry RS232 signals (115200 baud rate) over a USB cable? I don't want to use FTDI's RS232-USB converters. I just want to carry TXD, RXD and GND signals over a USB cable. Are my ...
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3 votes
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TTL to 232 with no conversion?

I was reading a blog about someone's application to ingest a TTL signal to a device and got perplexed. The author connects what appears to be a 3.3V TTL signal directly to a RS232 port (and it ...
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1 vote
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Custom ATMEGA2560 with RS-232 Communication Problem

I made a custom PCB using ATMEGA2560 with 2 MAX3223 RS-232 ICs (because they were available to me) but only one Tx channel is working on both ICs and I can't receive anything on any of them. I tried ...
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M-Bus level converter

Hello I am looking for an M-bus level converter. It has to support rs232 for hooking it up to a raspi. I have 5 slaves so 20 unit loads should be sufficient. I am not able to find a suitable product ...
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2 votes
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Opto-isolated RS232 signal capture

I have a problem in which I need to capture (spy on) an RS232 signal through an opto-isolator. This isolator needs to be high speed since the RS232 signal can reach up to 115200 baud. The main problem ...
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1 vote
1 answer
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3.3V TTL to other formats and impedance matching [closed]

I am trying to convert a 3.3V 50 Ohm Impedance TTL Pulse-per-second into other formats (GPIB, USB, RS-232, etc.). I've found some format adapters/convertors like the MAX232, but I am either ...
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