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Barcode scanners (Netum Scan) in python

I'm writing code which takes input from several barcode scanners, and I want a way to differentiate between each scanner. I'm on windows 10, and my python version is 3.11.1. And as the title suggests, I'm using scanners from a company called Netum.
I've tried using them as HID devices, but this seems incredibly slow and impractical. If the computer sees them each as keyboards, I have to validate each individual keystroke, rather than entire barcodes. So I've abandoned this approach under that assumption.
I discovered these scanners have what's called "USB COM Port Emulation," and that seems promising. It almost never works, but when it does, it just shoves an entire barcode into my code as a string. The problem is that, most of the time, when it's in this mode, it disconnects the USB dongle the instant I scan anything. But it makes a reference to "needing drivers" for this mode. I checked the device manager, which tells me all my drivers are totally up-to-date. This is really the crux of the problem, as my code works if this mode works reliably.
Also, I'm using PySerial to decode the inputs from the scanners. I dunno if that matters, but I figured I'd mention it. The following is the code I'm using to talk to these janky scanners, and it only works when the scanners don't disconnect from my PC for seemingly no reason.
import serial
scanner = serial.Serial(port='COM3', baudrate=9600, bytesize=8, timeout=1, stopbits=serial.STOPBITS_ONE)
string = scanner.read()
print(string.decode())
scanner.close()
If anyone has any advice, insights, or even just general directions to point me in, it would be appreciated. I'm at the point where I don't even know how to begin solving this.

Comment to answer
Have you installed any Virtual Com Port (VCP) drivers such as from FTDI? ftdichip.com/drivers/vcp-drivers They do a executable for easy install - this may help with your stability issues

Turn off specific USB port in windows with python

This is my first post, and I kind of have seen that the more specific the better, so I'll try to be super clear, and thanks in advance!
What I want:
I need to scan images from 2 or more scanners at the same time, these scanners are from the same brand and model, in this case Epson Perfection V600, I need different time intervals for at least 40 captures over a course of 20 hours.
My approach
I decided to use Windows, I already have a program in Python that does what I want with just one scanner, or with two from different models. But here is where you guys come in:
The problem
Windows always prints with the same scanner, Since they are from the same brand and model it always uses the same one, and I cannot use two different scanners because that will cause the images not to be comparable. Nevertheless, when I use two different scanners, I don't have such problem. I need to find a way to print with each scanner. I thought in buying a USB hub and control it with python as well, but apparently given libsub implementation in windows, I will not be able to control it. So I'm currently Looking for a way to disable an specific USB port so the program will only recognize one device, scan with it, disable that one, re-enable the other one, and so on.
What I have access to:
Right now I'm using Windows 10, 64 bits, python kernel 3 in a python 3.5 version inside a Conda environment, conda version (4.5.11).
Ubuntu 16.04, 64 bits, with pyinsane working, in a python 3.5 environment inside conda (don't have the conda version at hand).
One Epson perfection V600.
Two Canon Lide200, working only in windows, because drivers are not available in Ubuntu.
What I have also tried
Using Ubuntu,
I thought it was a good Idea, but the Epson drivers webpage fails to connect to the repository containing the rest of the Epson files, letting me only partially download the files, I already tried to contact the owner of the Docky repository, but he fails to contact me.
The error:
W: The repository 'http://ppa.launchpad.net/docky-core/ppa/ubuntu Xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch http://ppa.launchpad.net/docky-core/ppa/ubuntu/dists/xenial/main/binary-amd64/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
when I manually try to enter the site's repository I found that
All links to XENIAL drivers are down, actually the whole Xenial
Folder is missing.
Also then thought it was a good idea to ignore this message, but I
Need the Epwoka driver to run Epson scanners in Ubuntu, and that
a whole problem by itself. Aside from that, is not known if Epson
Perfection V600 is going to be possible to be controlled by the
PyInsane lib, since is marked as untested.
Using Windows
I thought in buying an USB hub and to controlled as shown in this thread, but apparently is not possible in windows.
I already installed libsub, usb.util, libusb1,USB (for the core functions) and usb1, but I don't know (I think is not possible) to disable and re-enable a specific USB port with them.
Can't disable the drivers since that mean all USB will be down to connect with the scanners.
Device manager is not helping, because of the inability of telling which device is which.
Cannot change the name of the scanner (yes, printers can have specific names) but scanners can't.
Can't buy another scanner, I'm stuck with Epson.
My code for Scanning
import pyinsane2
def Scan(Device, dpi):
pyinsane2.init()
try:
pyinsane2.set_scanner_opt(Device, 'resolution', [dpi])
pyinsane2.set_scanner_opt(Device, 'mode', ['Color'])
pyinsane2.maximize_scan_area(Device)
scan_session = Device.scan(multiple=False)
try:
while True:
scan_session.scan.read()
except EOFError:
pass
Image = scan_session.images[-1]
finally:
pyinsane2.exit()
return(Image)
devices = pyinsane2.get_devices()
image_a = Scan(devices[0], 75)
image_b = Scan(devices[1], 75)
a = devices[1]
b = devices[0]
a == b #Different
a.dev_type == b.dev_type
a.model == b.model
a.name == b.name #Different
a.nice_name == b.nice_name
a.options == b.options
a.reload_options == b.reload_options #Different
a.scan == b.scan #Different
a.srcs == b.srcs #Different
a.vendor == b.vendor
I put a sticki note inside each Scanner, one with an "a" the other one with a "b" and it always scans with the scanner that I plugged in first
This is what I would like to do (and doing it manually works): .
This is what I get when trying in python:
Any solution will help me, get creative! I was thinking on using a .bat file to disable an specific port and calling it with Python. But I couldn't find a way to make it.Keep in mind that doing it manually is not an option 'cause of the 20 to 40 hours of continuous image acquisition.
Thanks!
~Diego

Raspberry Pi 3: Unusual behaviour with mpd, PiFi DAC+ audio

I'm looking for some help 'cause I'm getting a bit frustrated on this... :-(
I have a headless Raspberry PI 3 with a PiFi DAC+ audio card, basically an HiFiBerry clone. On the PI I installed mpd and mpc as a client.
On top of those I wrote a python script that invokes some mpc commands to control the underlying mpd daemon (load a playlist, play a stream,...).
Now the issue.
The overall audio setup based on the hifiberry-dacplus overlay works well, the sound is good and I'm fine with it. Mpc & mpd work, I can control all the functionalities of mpd (at least the ones I need) through mpc without a flaw...but, if I try to run my python script suddenly I cannot hear anything anymore, even if no specific errors are traced.
The 'scary' thing is that, after aborting the script execution, I'm no more able to play any sound (I tried with several wav files using aplay), and again no specific errors show up in the log files...looks like someone just 'muted' the volume, but alsamixer shows all playback levels to 100%. I need to reboot the PI to get my sound back.
I checked for clues in the usual places:
/var/log/messages
/var/log/syslog
dmesg
boot.log
/var/log/mpd/mpd.log
I also run aplay -vvv when audio was blocked and compared the output with a session where audio was running fine but I didn't notice any difference...
I know it would be very difficult to diagnose the problem without having access to my system, but do you have any ideas on where else to look to understand if something went wrong?
Just for info, here's my aplay -l output:
**** List of PLAYBACK Hardware Devices ****
card 0: sndrpihifiberry [snd_rpi_hifiberry_dacplus], device 0: HiFiBerry DAC+ HiFi pcm512x-hifi-0 []
Subdevices: 1/1
Subdevice #0: subdevice #0
Thank you!
Michele
EDIT: seems like there is some incompatibility between the audio board and a 16x2 LCD display I'm using to show the name of the stream I'm playing. The display is a very common one, based on the HD44780 chip.
My code uses the AdaFruit python library available here to drive it and I still have to figure where the problem is: the audio board, as per HiFiberry docs is connected through GPIO 2,3,18,19,20,21 (plus ground & +5V for power), so it shouldn't cause any conflict with the LCD which uses different pins, but I wouldn't bet on it.
Anyway, removing the LCD management part from the python code (but leaving the display physically attached to the RaspBerry pins) apparently solved the problem...
I'll keep this question updated, maybe could be useful for someone else, who knows!

Ok, I got it. As usual, I just went too fast with CTRL-C & CTRL-V without properly reading the code...
I didn't notice I left this statement in my python code
lcd_backlight = 2 #GPIO pin to control lcd backlight
Actually The GPIO 2 (which is one of the two I2C enabled pins on the Raspberry) is not connected to the LCD, but it is used by the audio board for configuration purposes: this way, whenever I tried to initialize the LCD, the audio board was somehow reconfigured, making it "mute". The only way to reset the faulty configuration was to reboot the PI itself.
Just leaving the default 'None' value for the backlight control pin (I do not need it) did the trick.

How to use FDTI chip in VCP mode?

I'm trying to get a SainSmart USB relay board based on the FT245RL chip working and having a terrible time. I was under the impression that I could control the relays from the command line with something like:
echo -e -n "\xFF\x1\x1" > /dev/ttyUSB1
While the device is mounted automatically and I think I've got the baud rate and permissions set up, nothing happens on my Debian squeeze or CentOS 5 machines. SainSmart's support is worthless.
I decided to try on windows, so I installed the drivers and wrote a small program in python:
import serial
ser = serial.Serial(2) #COM3
ser.write(chr(255) + chr(0) + chr(1))
ser.close
Still nothing. Perhaps it's a hardware problem so I install a provided windows program. It sees the device and works when I click on the relay buttons. Discouraged, I exit their program, look for bugs in mine (can't find any) but try it anyways, and it works! I write a much bigger program to do all sorts of cool things and cool things happen until I unplug the device. When I plug it back in, nothing works. I've got to run and exit the relay control program before my code will do anything.
I suspect that I've got to do something with d2xx drivers like FT_SetBitMode(). Is there any way to just use VCP mode? PyUSB won't install on my computer and isn't available for Linux.
All I want is a simple way to control a relay on Linux using python.

I had the same problem, I think you were right about FT_SetBitMode(). Eventually I got it to work by using ftd2xx (which you can get by pip). You will also need to install the D2XX drivers.
import ftd2xx
if ftd2xx.listDevices() < 1:
print "No relays found. Exiting..."
exit()
else: print "Initializing relays..."
relays = ftd2xx.open(0)
relays.setBitMode(255,1) # I think this uses FT_SetBitMode()
relays.write(b'\01\01') # relay one on
relays.write(b'\01\01') # relay two on
relays.write(b'\00\00') # all relays off
relays.close()

I would first suggest you to try out hyperterminal first.
From your code snippet it seems that you are missing the baudrate (assuming the rest are going to be the default values). And I don't really know if it matters but I always explicitly set the port as Serial('COM3'), one less possible point of failure this way :)

Probably you don't have a problem with Python, but with controlling the device as such.
You should try to find out if the the device has special requirements about the state of the control lines (DST, DTR etc.).
And, not to forget, the communication speed which Alex already mentions.

Using virtual com ports on Windows I found I had to use 115k baud

Can a device have two UMDF Drivers?

This may seem like a bit of an odd question, but I was wondering if it is possible to associate two drivers with a peripheral device?
The reason I ask is that I am building an input device for Maya using an Arduino microcontroller. The Arduino already has its own device driver, but I was thinking of developing a UMDF driver to take the data that comes in from Arduino over the serial port and pre-process it ready to go into Maya.
Right now, I have two Python programs running - a 32-bit Python program running outside of Maya which listens to the serial port and converts the data to a form which a second 64-bit program inside the 64-bit version of Maya can understand and use in the Maya scene. This works fine, but it is a bit annoying having to start that external server program every time I want to use this device in Maya. If I can have a UMDF driver ready to jump into action when the appropriate type of data comes in off the Arduino then this would help immensely. Will this approach work?

It's more a comment/suggestion than an answer, but maybe it would be worth to invest some time and check if the filter driver would do the job for you. In WDM you can put it above the kernel device driver on the driver stack for that device, and use it to pre-process your device data. I think it is also possible in UMDF.
See Creating a New Filter Driver (MSDN).

You may always try to use Teensy/Teensyduino instead of Arduino to implement a virtual keyboard, mouse, joystick or other HID device. This does not require Windows drivers, and accessing the keyboard or joystick from Maya may be easier that the serial port.