Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

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.

First thing: the name RS-232 has been obsolete since eons. The "RS" means "Recommended Standard", but it's a well-established accepted standard now. Today it's known as EIA/TIA-232, but often just EIA-232 is used.

EIA-232 was originally designed, in pre-PC times, as the electrical interface between DTE (Data Terminal Equipment, the computer terminal) and DCE (Data Communication Equipment, the modem). With the advent of PCs it's been used more to connect computers directly together, without the DCE in between. To allow this, the straight DTE-DCE cable had to be modified to a so-called null-modem.

EIA-232 only specifies the type of connector and the pin assignments, and the voltage levels. The data format, UART is often used, is not part of the standard.

EIA-232 makes use of single-ended connections. The minimum for bidirectional communication is Signal ground, TxD (Transmit data) and RxD (Receive data).

Further reading

Difference between UART and RS-232?
Why does RS-232 need a stop bit?

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Why does RS-232 need a stop bit?

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 communicating at 9600BPS. We go from high to low,…
Utku
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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 to mean TX being the pin that sends data from the…
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How can RS-232 DTR / RTS pins be used for power?

I want to interface to this device where (sec 4.2) states can be powered from the DTR and RTS handshaking lines by having one high and one low Also, Wikipedia states: No method is specified for sending power to a device. While a small amount…
akellyirl
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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?
shafeeq
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RS-232 switching

I have a modem connected to a server through RS232. The server is constantly sending data to the modem, whether the modem is connected or not. When I try to connect to the modem with another modem the handshaking fails because the server is sending…
Handshaking
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How to connect uC to PC using RS232 with minimum number of signals?

The standard 9 pins RS232 connector has 9 pins. Those are: 1 -- DCD -- Data Carrier Detected 2 -- RxD -- Receive Data 3 -- TxD -- Transmit Data 4 -- DTR -- Data Terminal Ready 5 -- GND -- Signal Ground 6 -- DSR -- Data Set Ready 7 -- RTS -- Request…
mazurnification
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Is "RS-232 Cable" a valid term?

As "RS-232" is a Protocol/Standard, "DB-9" is a type of Connector, Is RS-232 Cable a valid term? Or is there any proper name for that? "Serial Cable" maybe!
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Making libftdi work with PL-2303HX

I want to bitbang a Prolific PL-2303HX. There is the library libftdi which enables bitbanging on the FT232 chip. Can I make it work with PL-2303? When I try using libftdi it gives in the error "Can't open device". Anyone knows how to make this…
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Force RS-232 DTR active

I have a vending machine that has a RS232 port. I'm trying to get data through another protocol called MDB to get telemetry data, but I really think that it only outputs data through MDB if the RS232 port is active. My plan to test is to force the…
ricreis394
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Need to create a circuit for a Man in the Middle Attack

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 2013 and I can't change it beyond that year without…
henda79
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In what way is a Craft Port different from a conventional RS-232 Port

In what way is a Craft Port different from a conventional RS-232 Port? It seems to be similar. Are there any interface or other important differences? Does craft port imply a higher level protocol on top of RS-232 as well?
dpp
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rs-232 theoretical maximum speed

I've read that speed of rs-232 depends on length of cable. There are many different tables that describe this dependency. But speed although should depend on voltage of Rx and Tx signals. How maximum theoretical speed of rs-232 depends on voltage?…
wshakura
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TI MAX3237 TTL / RS232 transciever, transmission not working

I've got a TI MAX3237 5 TX / 3 RX transceiver (TI datasheet, Maxim datasheet) set up as follows: The supply is 3V3 from a BeagleBone Black, measured at 3.35v. The CMOS level inputs and outputs (T1IN, T2IN, R1OUT, R2OUT) are taken out to headers,…
cb22
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Is possible use driver and receiver from different RS232 IC?

I need RS232 IC with Features: power supply 3.3v, ESD protection, 8-drivers/8-receivers. I'm looking for ic with these specifications are not found. These needs can be met if I use two IC is SP3244E (3-driver/5-receiver) and SP3249E…
new bie
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How to correctly wire RS 232 when data and power inputs are from different devices?

I'm trying to get nav signals from my flight simulator to my hand held GPS. The GPS (an Aera 796) sits in a cradle with bare wires coming out that would normally be tied into devices and power behind the panel of a plane. Here's the install pinout…
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