Hardware :: Reading Serial Port With C?
Aug 12, 2010
I have two usb2serial adapters connected to my PC with a null modem (I am doing some testing to learn serial comm for a particular application). I am writing to /dev/ttyUSB0 a trying to read /dev/ttyUSB1. I have used screen (screen /dev/ttyUSB1 115200) and am able to see the characters being written. I am also able to read and write with Python with the following code
Code: import serial,time,sys
ser1 = serial.Serial('/dev/ttyUSB0',baudrate=115200)
ser2 = serial.Serial('/dev/ttyUSB1',timeout=2,baudrate=115200)
ser1.open()
ser2.open()
[Code]....
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Aug 31, 2009
I have got a problem while reading from the serial port. I'm working on iMX-31 board and Eclipse IDE. Whenever I'm trying to read any data through the serial port, it's displaying I/O Possible and the application is being terminated. After reading I'm trying to write this data on a file. Here are the excerpts from the code:
# int main()
{
if (openport()<0)
[code]...
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Mar 5, 2010
I have an application where I am sending data via serial port from PC1 (Java App) and reading that data in PC2 (C++ App). The problem that I am facing is that my PC2 (C++ App) is not able to read complete data sent by PC1 i.e. from my PC1 I am sending 190 bytes but PC2 is able to read close to 140 bytes though I am trying to read in a loop.Below is code snippet of my C++ AppOpen the connection to serial port
Code:
serialfd = open( serialPortName.c_str(), O_RDWR | O_NOCTTY | O_NDELAY);
if (serialfd == -1)
[code]...
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Jan 13, 2010
I am trying to get two way serial communications going between a Windows XP system and a Linux system (RHEL 5).I have /sbin/agetty -L 9600 ttyS0
in /etc/inittab. I am using a generic USB to serial adaptor on Windows (Unitek) and a null modem cable. I have putty configured for 9600 baud, 8 bits, no parity, one stop bit, no flow control.I get the login prompt from agetty in the putty window but input does not work; I see weird characters in the putty screen. I can echo output into the device from windows and see it, but
cat < /dev/ttyS0. just prints out weird characters from what I type.
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Mar 23, 2010
We have a new machine with RedHat enterprise 5 on it. I need to connect a serial cable to the serial port and talk to another system (old alpha system) instead of using a VT connected to the alpha.Does RedHat come with anything like Keaterm/hyperterm/etc etc?
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May 10, 2010
I'm trying to set rxtxSerial to work so a Java app has access to a serial port (via SiLabs CP210x driver, port /dev/ttyUSB0). When I use update-alternatives --config java, there are 3 alternatives which provide `java'. I have tried openJDK and Sun. Both fail but with completely different messages.
[Code].....
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Apr 9, 2010
I have a configuration consisting of:
1. my Atmega168 MCU connected to some servo motors and sensors, and
2. my Linksys WRT54GL router working under OpenWRT Linux WhiteRussian 9.
3. they have a working and tested serial connection.
Now my problem.I open a file descriptor to my serial port called /dev/tts/1, and read a sensor (the second sensor commented, as you see bellow). This works perfect. Then I uncomment the next
sensor, but the code continues to behave as if I didn't uncomment it!If before the reading of the next sensor I first close my original file descriptor and reopen it, it starts to work right, but this is inefficient, as I have various sensors and it is not logical to open
[Code]...
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Dec 5, 2008
I am about to write a program to listen and read data from /dev/ttyS0 and write the data to /dev/ttyS1 after processing. Also, the same time I need to listen to /dev/ttyS1 and write to /dev/ttyS0 if any data arrived at /dev/ttyS1.
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Oct 1, 2010
I need to read raw codes from various remote controls (for TVs, DVRs, etc). For that I use a Tekram IR-210B serial dongle. At least I try, since I can't put any meaning on the codes I get by reading /dev/ttyS0 . I tried various tricks, including reading /dev/ttyS0 as a stream, using the Linux irda stack, lirc, similar experiments with Windows 2000/XP too, but nothing seems to work (at least not as I am expecting). The technical documentation is non-existant, Tekram e-mail support doesn't answer (or returns non-existant user errors when it does), browsing the kernel file tekram.c didn't help either, so I'm kind of stuck.
Because I won't need this for more than a few days (or weeks at the very most), I don't need a rock-solid solution, what I need is nothing mode than read raw (presumably RC-5) codes from a few remote controls (2 of them being from mainstream brands, another one claiming to be universal). So if nothing else a dirty trick will perfectly do.
Ideally, a technical documention on how to get the raw codes from the remote controls is what I am looking for. Something that tells me what baud rate to use, which parity, number of stop bits, and how to decode the stream (as I suspect it doesn't contain the raw codes as-is). However, I will be happy with any advice you may have on where to look or what tricks I might try.
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Feb 5, 2010
I am writing some application in C, which will access a serial port device (RS232). My application is working good. But if any other application is already opened the port, I couldn't able to identify that. In windows VB program, while accessing comport through mscomm control, i am receiving an error as "Port Already Opened". But in Linux environment, through C program how can i get that? I am accessing comport 1 as follows
fd = open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_SYNC);
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Jun 29, 2010
Working on a project based on embedded linux. The system is based on an Atmel ARM9 processor.
On one of the ports, an USB-A, we are constantly talking with several pieces external equipment (hereafter called slaves) at the speed of 4800 baud.
The communication is designed so that one messages is sent to a certain slave. The answer is expected to arrive directly. If no answer is received within 2 seconds, the sent message is sent in a resend buffer, and will be sent next cycle.
My problem is now that sometimes, the answer isn't received in 2 seconds. But when the message to the next slave is sent, the answer from the previous slave is received.
That is at least how it looked like from my software point of view.
But, then I used a serial sniffer on the USB port, and found out that the answer actually did arrive in time. Thus the delay must be somewhere between the USB port and my software. Linux in other words?
My software uses standard functions read() and write() for the communication.
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Mar 25, 2010
Can anyone one give me some pointers please, for talking to a serial port, if I use cutecom it always returns "could not open /dev /tty0 or 1 or 3 or 4, even tried ttys0 etc
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Jan 19, 2011
i would like to connect to my cisco via a console port and i dont konw how
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Apr 14, 2010
I have a laptop which has only one serial port.
I went into:
How do I know which of those "ttyS" refers to my serial port?
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Apr 27, 2011
ive been looking through several online documents and forum posts but i cant get a clearcut answer on how to set up serial port acces in ubuntu 10.04 (server).
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Feb 6, 2010
How do I get syslog using serial port?
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Jul 11, 2011
I can't communicate with and UPS (Eaton) via a serial port. The serial port is UP and have been tested under a Windows OS.I have set up the communication parameters and tried to establish a dialog with the UPS. Minicom is installed. Nothing appears ont the screen and the VT102 has an offline status. The OS is Red Hat Enterprise Linux 5 64bits.Is somebody have examples to debug the serial port ?
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Jan 25, 2011
I need cause an interrupt on a serial port. If I put a single HIGH on the RX pin, will that cause one? I all ready use the 4 control lines for data.Hope I am making sense?
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Apr 14, 2009
I need a to add a usb serial port adapter. Are they all basically the same? Do I need to find a Linux compatibility list before I go shopping?
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Apr 27, 2010
I want to implement the following scenario :-[workstation1] <--ETHERNET-->[device 1]<--SERIAL-->[device 2]<--ETHERNET-->[workstation2]In short, a LAN over Serial link (RS-232 for instance).If there is a utility that offers such functionality, kindly give me the name, i've googled a bit, and found ser2net, but that only works with TELNETing.. i want it work like a normal LAN like file-sharing n all but over Serial.If there is no such software, then obv i have to program myself. regarding which i have more questions
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Apr 15, 2010
can we use inb() and outb() functions for serial port programming ??
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May 25, 2011
I'm not a developer or programmer just a user.I'm trying to install a packet radio system using Linux. The TNC is a Kantronics KPC3.The issue I'm having is the communications programs I have tried (minicom and cutecom) do not talk to the TNC. I'm using a computer that has a serial port and it is enabled in the BIOS.I have added myself to the uucp group in an effort resolve this issue.
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Mar 23, 2009
I communication with different subsystems using serial port. In some subsystems after running for a while, I start getting invalid data inspite of system sending correct data. For dealing with this situation I used to
reset serial ports by closing and reopening serial port, it was doing the trick but somehow when I have implemented this in my new application, this also doesn't work.
void CPort::
The ClosePort function invokes close system call.
some other way to reset serial port in Linux? I am using RHEL 4, C++ and Qt 4.2.1 for my application development. Also I have used multithreading to implement each subsystem in a separate thread. Its strange that if A,B,C are three threads, A & B run fine together but when C is introduced B starts receiving invalid data after sometime and never recovers even after resetting the port as mentioned above.
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Jan 13, 2010
I dot know why my serial port(minicom) is getting hang after some time. again i have to close the terminal and i have to open an new minicom to use my serial port. I dont know why it is getting hang. Please can anuone tell me why it is happening?
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Sep 1, 2010
I'm using C serial in a program to open and use a serial port but the port won't open for one reason or another. The program successfully runs on a different computer and when using RealTerm: Serial Capture Program, I can connect through the serial port with the same settings as I'm attempting through my c code. Anyone have any idea why it might be failing? I know this is still pretty vague, so let me know if there's other things I can tell you that might help to finding a solution
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Apr 27, 2009
The /dev directory on my system shows the following entries:
/dev/tty
/dev/tty0
/dev/tty1
[code]....
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Jan 16, 2010
I would like to be able to ssh to a TCP port on my server and be directly connected to the serial port @ 115200 Null modem config. Does any body know how one can do this?
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May 24, 2010
My program tries to open serial port on Fedora 12, and shows "Access denied" on Open Port operation. The same program runs successfully with root rights. What can I do to get COM port access as regular user?
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Sep 24, 2010
I think I need to mount a serial device, but not sure how. I looked at /etc/fstab, but cannot determine what to put in for the mount type. And, not sure what port it would be exactly... imagine either "ttyS0" or "tty0". Can someone give a newbie some guidance on how to possibly mount this device?
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Jun 7, 2011
have a new HP Compaq 8200 elite. I have a dual boot system. Windows 7 and Fedora 15.In Fedora I cannot seem to connect to the serial port. Could anyone help me with resolving this. I've never had issues with hardware before in Linux so this is a little new to me.
Code:
[matt@matt ~]$ dmesg | grep tty
[ 0.000000] console [tty0] enabled
[code]...
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