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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Difference between UART and RS-232?

Most of the time RS-232 and UART come together in serial communication theories. Are they both the same? From my readings I concluded UART is a hardware form of the RS-232 protocol. Am I correct?
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Capacitor in RS232 level shifter. Data is strictly half-duplex

I have created a level shifter very similar to the schematic at: http://picprojects.org.uk/projects/simpleSIO/ssio.htm except for the capacitor I use 47nF because the page claims: at high bit rates ...
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7 votes
2 answers
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Problems with homemade RS232-to-TTL converter board based on TI's MAX232

I've designed an RS232-to-TTL converter board based on TI's MAX232 IC that I plan to use to program a few custom Arduino boards that I have. However, I'm having trouble with the board and I'm hoping ...
Ricardo's user avatar
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6 votes
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RS 232 serial sniffing

We have a task in hand to sniff a RS232 protocol in a certain industrial automation setting (we have been asked to do this legally by the manufacturing company itself). We are planning to send a ...
Elsa Adams's user avatar
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5 answers
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Can I use 10\$\mu\$F caps in a MAX232?

this is just a quick and dirty question. I don't understand the purpose of the 1 \$\mu\$F caps in the MAX232 circuit. What do they do, exactly? Can they be skipped? Can they be swapped with 10 \$\mu\$...
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17 votes
6 answers
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Max Serial Cable Length?

What is the maximum length of serial cable I can use, to connection work properly? Is length of serial cable in connection with baud rate? I am using about 5 meter cable at speed 38400 bauds and RS232 ...
Junior's user avatar
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14 votes
3 answers
7k views

Why does RS-232 need a stop bit? [duplicate]

This might be obvious but I don't understand why RS-232 needs a stop bit. I understand that the start bit is necessary to notify the other end about the beginning of a transmission. Let's say we are ...
Utku's user avatar
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4 votes
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How does this PIC board achieve RS-232 communication without a line driver?

All the develooment boards I have seen yet with serial communication support usually have MAX232 line trasceiver. However, I have come across this Olimex PIC-LCD development board that does not have ...
quantum231's user avatar
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RS232 hotplugging

I've noticed that when I connect/disconnect the RS232 cable to my micro-controller, I receive a garbage character at the other end (my pc). Is there a way to prevent this? I want to eventually move ...
Bob's user avatar
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7 votes
2 answers
14k views

Implement serial port on fpga (verilog)

I don't know if this belongs here or stackoverflow. I assume here as although verilog looks like software it's actually describing hardware connections? I have a Spartan-3AN evaluation board and I'm ...
John Burton's user avatar
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1 vote
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Connecting GSM SIM900A module with Ardunio

I have bought an SIM900A Mini V4 GSM module. Here is the module, I want to configure with arduino to send and receive SMS. Do I have to connect TXD of this module--Tx of Arduino & RXD of this ...
Jeyanth90's user avatar
1 vote
2 answers
1k views

Speed problems in homemade RS232-to-TTL converter board

I'm still trying to debug this RS232-to-TTL converter board that I've made, shown below. Now I think I've narrowed down the problem to speed: it works fine at 57,600 baud; but it inserts some ...
Ricardo's user avatar
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24 votes
8 answers
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Communication between multiple microcontrollers

I'd like to start implementing a system consisting of N microcontrollers (N >= 2 MCUs), but I would like to know the possibilities to let them communicate one with the other. Ideally, (N-1) ...
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21 votes
2 answers
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What is the meaning of "half bit" in this context?

In RS-232 specification, the stop bits can be 1, 1.5 or 2 stop bits...I wonder how it's possible to have half a bit? Also some ADC math uses 0.5bit precision in the IC specifications/datasheet. Can ...
mFeinstein's user avatar
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11 votes
2 answers
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How does the MAX232 double the voltage?

MAX232 Datasheet Hi, I am currently a student so bear with me please! I'm currently using a powering the MAX232 with 5V DC, and when I measure from VCC to lets say, pin 3, I am getting a voltage ...
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9 votes
2 answers
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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 code ...
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4 answers
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What can I do to decrease the latency from these serial ports which are attached to a PC via a Serial to USB adapter?

I think I have accidentally discovered a need in my life for embedded systems. Which is great! And kind of scary. And I need help. Background: I got hired to build a GUI application which takes scans ...
canisrufus's user avatar
8 votes
3 answers
21k views

What is the maximum acceptable baud rate error for RS-232 serial communication?

What is the maximum clock difference between a transmitter and receiver for error-free asynchronous serial communication?
markrages's user avatar
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7 votes
5 answers
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RS-232 Buffer circuit

I wanted to sniff communication between two RS232 devices. This link presents a simple solution but I want to make sure that my 'sniffer' does not load the communication link. To that effect, I was ...
itisravi's user avatar
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6 votes
7 answers
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Best PC interface for simple custom hardware

What interface of your PC do you use in order to connect to simple custom hardware? The most commonly used interface was RS232 some while ago and today is probably USB, but wouldn't it be simpler for ...
Penguin Nurse's user avatar
6 votes
4 answers
12k views

Do I need MAX232 when using USB-to-Serial cable?

I am willing to build an AVR JTAG debugger (I grabbed from here: http://aquaticus.info/jtag) but the circuit uses COM port and it has MAX232 transceiver. My Laptop does not have COM port, so I need a ...
Siraj Muhammad's user avatar
4 votes
2 answers
646 views

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 ...
dreamcoder's user avatar
3 votes
3 answers
717 views

Doubts on Implementing a Simple Protocol for XBee Comms

A system that I'm developing will use XBee modules for a point to point connection between a micro-controller and a PC. Data will only be sent only in one direction -Micro to PC and at 10-20fps. The ...
volting's user avatar
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3 votes
2 answers
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Disadvantages of USB to RS232 dongles

I understand (or am learning, rather) how both RS232 and USB work. What I am really curious about, and can not seem to find much information for, is what kind of disadvantages do USB to RS232 dongles ...
lakechfoma's user avatar
2 votes
1 answer
784 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 ...
cdleary's user avatar
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2 votes
2 answers
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How to protect a MAX232 from PIC programming high voltages?

This question is derived from this Board review thread, I thought it would be preferable to make it a standalone question. I want to be able to reset a PIC remotely using the only communication port ...
user42875's user avatar
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2 votes
2 answers
1k views

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 ...
Wisteso's user avatar
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1 vote
0 answers
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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 ...
tgpaul's user avatar
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1 vote
1 answer
453 views

TTL RS-232 current limiting

I'm making software UART (TTL levels) on ATtiny85. Need I connect current-limiting resistor to output (TX) port? If "yes", what value should I use? I plan to connect my device to a UART-USB converter ...
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1 vote
2 answers
7k views

RS232 wire color

I have RS232 wire and want to take form it a ICSP end for my serial AVR programmer , I find it difficult to assign colors to pins ,so is ther any standards . the color I found after cutting the end ...
Yahya Tawil's user avatar
1 vote
2 answers
3k views

How would I make an Arduino Due recieve RS-232/422 signals?

Background on this question is here: What can I do to decrease the latency from these serial ports which are attached to a PC via a Serial to USB adapter? I'm looking at purchasing an Arduino Due to ...
canisrufus's user avatar
1 vote
1 answer
1k views

Driving relay with PC serial port fails after few hours

Ive been trying to use this schematic: to drive relay (from this answer). (Components are as specified in schematics, with D2 being 1N4007) ...
Matija Nalis's user avatar
1 vote
3 answers
7k views

LG RS232 Commands partially working

I have a LG TV (32SL8000), which has a RS232 Control Port. I tried to control it with an Arduino and a TTL to Serial Converter (MAX3232). I looked up the commands from the manual. ...
Apatus's user avatar
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4 answers
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Cannot communicate with serial device via an Arduino Nano serial communication

I am trying to communicate with an RFID reader via its serial port. The serial port has an RS232 connector on it. I also want to display the RFID tags ID on a 16x2 LCD screen using an Arduino. I, ...
JoeyB's user avatar
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1 answer
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Learning about security of UART and RS232 [closed]

I'm trying to learn about UART and related problems and solutions. IIUC, UART is a hardware, RS232 is an interface and hyperterminal is a program. Would these parts be able to work together? I ...
Niklas Rosencrantz's user avatar
0 votes
2 answers
919 views

3.7v > 3.3v voltage stepdown with logic-driven on/off control [paused]

(PAUSED): This topic is currently on hold as I source necessary hardware. I need to connect a Wi-Fi/RS232 module to a low-powered monitoring device, and for maximum portability, I'd like to power the ...
i336_'s user avatar
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1 answer
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RS232 and RS422 (Isolated and ESD Protected)

I want my RS232 and RS422 to be galvanically isolated and ESD protected. I have two options to implement this requirement. Option 1: MCU-->OPTO-->DRIVER-->ESD PROTECTION Use MAX3232 for RS232 driver ...
AKR's user avatar
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1 answer
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Questions about RS-232-like naming and standards

1. Is official RS-232 (EIA-232) standard open and free available? I couldn't find it in Internet. 2. Does "RS-232 with TTL levels" is covered by some standard? 3. Does "synchronous RS-232" (via ...
user avatar
0 votes
1 answer
387 views

Board review: is this PIC16F877 RS232+ICSP board correct/robust?

I want to make my own development board based on a PIC, to make a RS232 bootloader from scratch. It's been a while I haven't used a PIC, and it was on a ready made development board. I've looked ...
user42875's user avatar
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0 votes
2 answers
5k views

RS-232 to I2C communication [closed]

I'm trying to establish communication between two boards, one of which has an RS232 output and the other with an I2C input. I've looked for adapters online and the only ones I've found seem to be ...
Yasir C's user avatar
0 votes
1 answer
970 views

MAX3232 CAE outputs -6V / +6V instead of -12V / +12V

I bought a GN801 GPS module from Stoton ( http://www.stotoncn.com/gnssmodule/showproduct.php?lang=en&id=42 ) Power supply range is +5V. There is an onboard MAX3232CAE that is supposed to output ...
Laurent Coulon's user avatar
0 votes
3 answers
3k 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, ...
Xuttuh's user avatar
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-1 votes
1 answer
206 views

Using a laptop to communicate with an MBED module

I'm using an external power source to power an MBED module. I have the UART transfer and receive ports connected to a MAX232 level switcher in order to make the signals compatible with RS232. From ...
200ok404notfound's user avatar