Python Serial Port Is Already Open
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Basically, it implements everything needed for the RFC 2217 protocol.It just does not open sockets and read/write to serial ports (though itchanges other port settings). The user of this class must take care of thedata transmission itself. The reason for that is, that this way, this classsupports all programming models such as threads and select.
The serial_port can be controlled by RFC 2217 commands. Thisobject will modify the port settings (baud rate etc.) and control lines(RTS/DTR) send BREAK etc. when the corresponding commands are found bythe filter() method.
The actual reader loop driven by the thread. It callsProtocol.connection_made(), reads from the serial port callingProtocol.data_received() and finally calls Protocol.connection_lost()when close() is called or an error occurs.
I'm trying to write an App that uses serial ports in a Linux PC, using python and PySerial. But in this PC there are other Apps using serial ports. How can I know if a port is already open by other App before trying to use it?
To avoid this error I unplug my Arduino cable and restart Python but it doesn't help. In Matlab for the same problem, if we close Matlab, problem is solved but the same thing is not happening with Python. I want to know how to close this open port now. Even after restart my laptop, same error is coming.
I find this problem too.my serial is RS232 and just connect Grounding/RX/TX from my device to laptop.I just ignore the open step and the directly write cmd to serial, but I get the collect feedback.So, I guess we don't have to open serial before we handle it in some case
The line ser = serial.Serial('/dev/serial0', 9600, timeout=1) opens the device automatically. When you try to open the device that is already open, python raises an error. Just take out ser.open() and it will work.
The open() method of the SerialPort interface returns a Promise that resolves when the port is opened. By default the port is opened with 8 data bits, 1 stop bit and no parity checking. The baudRate parameter is required.
Before communicating on a serial port it must be opened. Opening the port allows the site to specify the necessary parameters that control how data is transmitted and received. Developers should check the documentation for the device they are connecting to for the appropriate parameters.
When running VPN software, you may occasionally get error messages like, "The specified port is already in use" or "The specified port is already open." What do these errors mean, and how can you fix them?
Another example of a nonsharable resource is a network port used by VPN software. In this case, the VPN software opens a network port through which all network communications are encrypted and forwarded to a remote VPN concentrator located in an organization's data center. Any application that opens the local network port needed by the VPN will cause the conflict.
A common cause of the "port already open" error occurs when a computer automatically goes to sleep to conserve power after a period of inactivity. The transition to sleep followed by reawakening causes the connection to drop. But the computer's OS doesn't release the lock it created on the nonsharable resource. The network application, upon attempting to reestablish the connection, encounters the locked resource, causing the "port already open" error message. Rebooting the computer clears the locked resource, and the network connection can be reestablished.
Another cause, though less frequent, is when another application also uses the network port that the VPN software is using. This was the case with a VPN software problem as described on the Cisco Meraki forum -- "Windows 10 VPN error: The modem (or other connecting device) is already in use." The solution in this case was to edit the Windows registry to prevent the other application from using the network port reserved for the VPN software. The linked articles above describe a step of using a Netstat command prompt to find the application creating the conflict.
The most frequent source of problems for non-Windows OSes is due to using Secure Socket Shell (SSH) port forwarding. When the SSH connection dies, an immediate attempt to use port forwarding may report a message: "Address already in use." This occurs because TCP must wait for the final handshake that closes the network connection, called TIME_WAIT (see Request for Comments 793). Waiting a few minutes will enable the application to reuse the network ports in question.
Once again, serial has nothing to do with serial buses. It does not coexist well with pyserial because they share the same import name. Do not install both in the same environment. Doing so is likely the cause of the weird errors you saw earlier.
J-M-L:I already told you that nothing buffers Serial Data you throw at your PC if no program has an open Serial port attached to this serial port. So when you launch your Script, the buffer is always empty, wether it's the first time you launch it or not, in_waiting will be 0 (or whatever arrived between the time you opened the Serial port and tested in_waiting)
I apologise but I really don't get what you mean, please help me understanding giving more details. When I create the serial port with serial.Serial("/dev/tty.usbmodem1225061", 115200)the port is actually created and the serial connection is open, right? Indeed as I said earlier .is_open() will return True.
frodojedi:When I create the serial port with serial.Serial("/dev/tty.usbmodem1225061", 115200)the port is actually created and the serial connection is open, right? Indeed as I said earlier .is_open() will return True.
This is the minimal python code that reproduce the problem. If you uncomment the line #read_byte = serial_port.read(size=1).decode("utf-8") appearing before the while True then you get that the second time you launch the script it works.
When I come back later I do not want to find old stuff in the queue. I want the new one. When I re-establish the connection calling the serial.serial(port, baudrate, etc...) then I simply want that the data that are arriving are read in the buffer, i.e. that in_waiting is > 0. This does not happen unless I call read(1).
I have multiple serial ports to each of which devices are connected. They are listed as /dev/ttyUSB*. Now, I need to make sure using a python script that no other process is using any of these before I run a kermit script (so that access is not denied) login_init. I tried ps and lsof commands. lsof gave the following output:
Problem 1 : Cannot open /dev/ttyACM0: Permission deniedSolution : Grant permissions to read/write to the serial port with this terminal command ---> sudo chmod a+rw /dev/ttyACM0Here replace tty port with your respective ubuntu port.
Problem 2 : Failed to open /dev/ttyACM0 (port busy)Solution : This problem appears when serial port is busy or already occupied. So kill the busy serial port with command ---> fuser -k /dev/ttyACM0. Here replace tty port with your respective ubuntu port.
Problem 3 : Board at /dev/ttyACM0 is not availableSolution : In this case your serial port in tools menu will be greyed out. I googled a lot for this, but I none of solution worked for me. Atlast I tried different arduino board and usb connector and it was working for me. So, if you are having old arduino board (can be solved using required drivers) or defected arduino board then only this problem arises.
When you type a character into the console, it will received by the Arduino, and it will send the corresponding ASCII code back. Check here for ASCII Table. And there it is, the Raspberry Pi is talking to the Arduino over GPIO serial port.
There might be two version of python on your pi (python2 and python3), and you only installed serial on python2, and you are using python3 to compile the code, that might be why you are getting this error.
I connect arduino Mega serial pins and raspberry type B GPIO with a adafruit voltage level converter I copied and pasted your code (python for Raspberry). Unfortunately when I type 103 in the arduino serial monitor, the raspbian terminal displays: character recieved: 1 character recieved: 0 character recieved: 3
More than likely you ran the Arduino program from the Arduino IDE, and left the terminal window open. You must close it before you run the python program, as it will already 'own' the port until it closes. You dont have to quit Arduino IDE, just close the terminal window.
Then within PSOC file, I have a UART that is able to read and write from a Com port too. Theoretically, I thought that if my python script wrote to a Com port, and my UART was connected to that same COM port, I'd be able to read information in. However, I have the issue that my python script will throw an error because the port is already open and I am not able to write to the COM port.
If my understanding is correct, you are trying to write to the same COM port from python which you have opened in another terminal software? And you want to push something to PSoC from Python and likely want to see the data in a terminal??
3. Connect the python interface pins to either a USB-Serial interface or another kit's UART pins (could be any kit that supports USB-UART interface - make sure the primary device in that kit does not load the UART lines). From the Python script, you can access the python interface COM port. 2b1af7f3a8