I've installed the Arduino virtual USB serial port driver, it's appeared as COM4 on my device manager. I double checked by listing all available serial ports in powershell
> [System.IO.Ports.SerialPort]::getportnames()
COM1
COM4
However, when I try to do an echo to the serial port, it says it does not exist
> echo helloworld > COM4
The system cannot find the file specified.
I am trying to upload some firmware in to my arduino, but I kept getting denied by the port. Trying a different USB gives me the same result. I wrote a small program to test the serial port and I get the error:
The serial port "COM4" does not exist.
The device name of a serial port on Windows is \\.\COMn where n is the port number. A device driver can emulate the DOS device name, like "COM4" if it chooses to do so, very simple to do in the device driver code. But that's an increasingly rare thing to do, especially for port numbers larger than 2 and extra especially for port numbers larger than 4. So seeing your echo command fail is not unusual.
A serial port cannot be shared, it can only be opened once by a process and everybody else that tries to open it will get the fail-whale ERROR_ACCESS_DENIED error code. Necessarily so, serial ports sit at the very bottom layer of the OSI model, there is no protocol that arbitrates access to the port. Or to put it another way, the operating system has no guidance on who should get the data that the port receives. There can be only one candidate, the process that opened the port first. So the error message you got is not unusual, you have to make sure that nobody else is using the port. Including the Arduino serial port monitor.
Related
I am trying to pragmatically control scanning operation of Gryphon I GPS4400 barcode scanner.
Scanner is attached to host over usb cable and scanner is programmed to act as virtual serial port.
I have control over serial port on host and I am receiving data from scanner regularly, also I am able to send some data to scanner over serial port. Scanner from my random text sent sometime response to serial port some time just beep.
I am trying to activate scanning mode:
Serial On Line: Scanning is initiated by command sent through the
host interface (manual triggering can be enabled in this read mode
through option setting).
(I know how to activate this mode on scanner, by reading configuration barcodes, but after that I do not know how to send command to trigger scanning)
My problem is that i can't find what sequence I need to send to scanner to start scanning?
Is it possible at all to control scanning by commands over virtual com port attached by USB or I need to have dedicated serial cable with special wiring ?
I have a device with a RS-232 DB9 port connected to my Raspberry Pi over a USB-to-serial cable.
Initially, I am able to communicate with the device without issue using pyserial.
However, after some variable length of time, I can no longer receive messages from the device.
If I close the serial port and attempt to open a new one, using the same code I normally use:
import serial
ser = serial.Serial(
serial_path,
9600,
bytesize=serial.EIGHTBITS,
parity=serial.PARITY_NONE,
stopbits=serial.STOPBITS_ONE
)
I get:
File "/opt/venv/lib/python3.8/site-packages/serial/serialposix.py", line 713, in _update_dtr_state
fcntl.ioctl(self.fd, TIOCMBIS, TIOCM_DTR_str)
OSError: [Errno 5] Input/output error
I have no way to get around this error and re-establish communication with the device unless I physically unplug and replug the USB port.
In case it's relevant, the RS-232 device is connected to my RaspBerry Pi via an intermediate USB Hub and a USB extension cable.
I also tried setting rtscts=True and dsrdtr=True when creating the pyserial object. The IOError no longer occurs; however the serial device remains uncommunicative.
What might be the underlying issue here? Any guidance would be appreciated. Is there any way to detect the issue and reset the serial port via the shell, without requiring physical intervention?
Currently I have a server, that communicates with a projector through a RS232. The server opens a com port when the projector is connected. The same happens to any PC when a certain type of device is connected through the USB (lets say an Arduino for example). What I want to do it basically replace the projector with a PC/Arduino/Raspberry without the server noticing anything. That would mean the server will recognise the connected PC and open a COM port for it. What do I need to do on the PC so that it automatically opens a com port on the server? I guess there is something very basic that any printer, Arduino, projector etc does, that computers recognise it as a "com port device".
P.S. Doesn't matter the OS on the PC, I just need to make it work and then implement w/e I need to do with the established communication over the port.
P.S.2 I've searched a lot about it, but probabl I am doing it wrong, because I didn't find my type of question anywhere.
COM ports are basically hardware that is detected by the system. Let's say, if an Arduino is connected to a PC, it has its onboard USB to TTL converter which can be found in the device manager(if using windows). Similar USB to TTL converters are there in the market like CP2102, PL2303 which acts like a COM port even if no device is connected further to it. it may be possible that the program you are using(as you referred server) may be sending some data over the serial port and verifying the hardware.
What you need to do to replace it is, first of all, find the baud rate at which the communication is going on, then, listen over the serial lines which machine is sending which message in the sequence(there must be a handshake as I mentioned earlier), if a complicated algorithm is not used by the device, you can simply mimic the device by sending same messages over serial.
I am working with someone using Mbed and a LPCXpresso11U68 board.
I'm not intimately familiar with this particular board, but it has two USB connectors on it, one for the OpenSDA-ish debugger, and a second one is a direct connect to the CPU. I can connect both of these ports to my PC and attach a terminal emulator to each of them, and both ports show output (with a small installed program running on the board).
The device manager shows me that one port (COM51) is using "mbed Serial Port" driver and the other port (COM52) is using "Mbed Virtual Serial Port.
So far so good...
There is a reset button on the board. If I press that button, the port that is attached to the PC using the Mbed Virtual Serial Port driver (in my case COM52) stops operating. The other port (COM51) just restarts cleanly.
The problem I'm having is that after I exit the terminal program (note this happens with both TeraTerm and uCon), if I attempt to reconnect to that port, its not in the list of available comports. Strangely thought, it is still present in the Device Manager.
The only way I've found that I can clear this problem is to unplug/plug that usb cable (COM52) or issue a BREAK condition to COM51 (which AFAIK, resets the board).
I am the writer of uCon and I'd like to be able to detect this (which I can), and also be able to restart the comport connection without any other manual intervention.
One final note: apparently this is not specific to the LPCXpresso11U68 board; my guess it is some issue with the Mbed Virtual Serial Port driver.
Anyone have a clue what may be going on here?
I bought this magnetic strip reader writer (MSRE106) and I use USB adapter to connect it to my laptop because I have no serial port in my computer. But now I have a problem since the software of the device recognizes only serial ports on windows. After looking up I found someone that wrote a python script for Linux (found here The Script).
Still even in this python script in the settings file it has this variable
## Com port.
COM = "COM1"
How can I change this to be one of my USB ports instead of a serial one because I have none
This script is made to use serial port as well, which means you can't just modify COM="USB1" or whatever to use your USB adapter. If you have a look at line 264 a serial port is open using function SerialPort().
To fix this issue you must install your USB adapter's driver that will emulate a serial port and create a fake COM1 you can use with this script or the original software of the MSRE106.