Develop Reference

VI_ERROR_TMO (-1073807339) on Anritsu OSA

I'm working on interfacing an old Optical Spectrum Analyzer Anritsu MS9710B with a RS232 connection. A year ago, I managed to comunicate with him, send SCPI command using pyvisa and receive data. Today, I execute the exact same code with libraries up to date and I get an error Timeout when I query IDN or anything. The RS232-USB drivers are ok, I manage to open a communication but a query or read fail.
I changed the parameter to "RS232C" on the OSA parameters and my communication parameters are the same between OSA and program. Following advices from the forum, I tried the connection with NI-VISA where I get the same error. I tried to change timeout parameter, write_termination and read_termination but there isn't any change. The manual is very hard to understand termination value, but when it worked I didn't add anything.
I don't know anymore what to do.
Any advices and help would be warmly welcome to fix my problem !
import pyvisa
from pyvisa.constants import StopBits, Parity
rm = pyvisa.ResourceManager()
print(rm.list_resources())
my_instrument = rm.open_resource('ASRL5::INSTR')
my_instrument.baud_rate=9600
my_instrument.data_bits=8
my_instrument.parity=Parity.even
my_instrument.stop_bits=StopBits.one
my_instrument.write('*IDN?')
print(my_instrument.read())```
'''
('ASRL5::INSTR',)
Traceback (most recent call last):
File "PremiereComm.py", line 26, in <module>
print(my_instrument.read())
File "C:\Program Files\Python38\lib\site-packages\pyvisa\resources\messagebased.py", line 486, in read
message = self._read_raw().decode(enco)
File "C:\Program Files\Python38\lib\site-packages\pyvisa\resources\messagebased.py", line 442, in _read_raw
chunk, status = self.visalib.read(self.session, size)
File "C:\Program Files\Python38\lib\site-packages\pyvisa\ctwrapper\functions.py", line 2337, in read
ret = library.viRead(session, buffer, count, byref(return_count))
File "C:\Program Files\Python38\lib\site-packages\pyvisa\ctwrapper\highlevel.py", line 222, in _return_handler
return self.handle_return_value(session, ret_value) # type: ignore
File "C:\Program Files\Python38\lib\site-packages\pyvisa\highlevel.py", line 251, in handle_return_value
raise errors.VisaIOError(rv)
pyvisa.errors.VisaIOError: VI_ERROR_TMO (-1073807339): Timeout expired before operation completed.
>>> '''

How to solve "control message failed, win error: A device which does not exist was specified" error PyUSB

I'm trying to connect a POS receipt printer to python and have been using python-escpos to do so. I'm running windows 10.
My code in my file 'print.py' is:
from escpos.printer import Usb
p = Usb(0x0456,0x0808)
p.text('Hello World\n')
but when i run it i get the following error log:
Traceback (most recent call last):
File "C:\Users\Harry\AppData\Local\Programs\Python\Python36-32\lib\site-packages\usb\core.py", line 223, in get_interface_and_endpoint
return self._ep_info[endpoint_address]
KeyError: 1
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "print.py", line 5, in <module>
p.text('Hello World\n')
File "C:\Users\Harry\AppData\Local\Programs\Python\Python36-32\lib\site-packages\escpos\escpos.py", line 437, in text
self._raw(txt.encode())
File "C:\Users\Harry\AppData\Local\Programs\Python\Python36-32\lib\site-packages\escpos\printer.py", line 73, in _raw
self.device.write(self.out_ep, msg, self.timeout)
File "C:\Users\Harry\AppData\Local\Programs\Python\Python36-32\lib\site-packages\usb\core.py", line 940, in write
intf, ep = self._ctx.setup_request(self, endpoint)
File "C:\Users\Harry\AppData\Local\Programs\Python\Python36-32\lib\site-packages\usb\core.py", line 102, in wrapper
return f(self, *args, **kwargs)
File "C:\Users\Harry\AppData\Local\Programs\Python\Python36-32\lib\site-packages\usb\core.py", line 215, in setup_request
intf, ep = self.get_interface_and_endpoint(device, endpoint_address)
File "C:\Users\Harry\AppData\Local\Programs\Python\Python36-32\lib\site-packages\usb\core.py", line 102, in wrapper
return f(self, *args, **kwargs)
File "C:\Users\Harry\AppData\Local\Programs\Python\Python36-32\lib\site-packages\usb\core.py", line 225, in get_interface_and_endpoint
for intf in self.get_active_configuration(device):
File "C:\Users\Harry\AppData\Local\Programs\Python\Python36-32\lib\site-packages\usb\core.py", line 102, in wrapper
return f(self, *args, **kwargs)
File "C:\Users\Harry\AppData\Local\Programs\Python\Python36-32\lib\site-packages\usb\core.py", line 239, in get_active_configuration
bConfigurationValue=self.backend.get_configuration(self.handle)
File "C:\Users\Harry\AppData\Local\Programs\Python\Python36-32\lib\site-packages\usb\backend\libusb0.py", line 510, in get_configuration
100)
File "C:\Users\Harry\AppData\Local\Programs\Python\Python36-32\lib\site-packages\usb\backend\libusb0.py", line 593, in ctrl_transfer
timeout
File "C:\Users\Harry\AppData\Local\Programs\Python\Python36-32\lib\site-packages\usb\backend\libusb0.py", line 431, in _check
raise USBError(errmsg, ret)
usb.core.USBError: [Errno None] b'libusb0-dll:err [control_msg] sending control message failed, win error: A device which does not exist was specified.\r\n\n'
Does anyone know what i need to do to make this work.
I have installed libusb into my System32 and SysWOW64 folders, aswell as installing a libusb-32 driver for my printer with zadig.
The printer i'm using is a 'Hoin 58mm POS Printer'.
I would be grateful if someone could explain to me why i'm having this error and how to solve it!

Firstly, you can check this link for the complete thread.
As suggested by KM4YRI,
I ran into the same No backend available exception when trying to follow the tutorial on a Windows 7 machine. The following worked for me, per one of the StackOverflow replies:
1. Download the latest Windows binary: https://sourceforge.net/projects/libusb/files/libusb-1.0/libusb-1.0.21/libusb-1.0.21.7z/download
2. Unzip using 7zip into a temp dir
3. If on 64-bit Windows, copy `MS64\dll\libusb-1.0.dll` into `C:\windows\system32`. If on 32-bit windows, copy `MS32\dll\libusb-1.0.dll` into `C:\windows\SysWOW64`.
I've verified the above answer on Windows-10 64-bit version.

I had a tight experience with that error using at least 3 different USB Storage Devices. After hours of trials I ended up to a feeling that USB transmission errors are the cause of this error.
The USB bus will return it in a random pattern for a low quality connection as if a device remove has presumably happened.
In my scenario I was bulk writing sectors to a \\.\PhysicalDriveN device and I noticed that after a short period the connection reestablished and the file handle was still valid and going.
To overcome the error I've ended up with the following steps:
Seek To File Position;
Write Sector;
For any 433 error:
250 ms delay;
Seek To file Position, ignoring ERROR_NO_SUCH_DEVICE and ERROR_NOT_READY errors and trying for at least 1000 ms before giving up;
Read Sector, ignoring ERROR_NO_SUCH_DEVICE and ERROR_NOT_READY errors and retrying for up to 1000 ms before giving up;
Specially for my scenario: I've compared input buffer and read buffer and stop if matching;
Repeat the whole procedure up to 5 times.
So the idea here is the following: The device driver returns ERROR_NO_SUCH_DEVICE assuming a device remove scenario, but still in a pending state. As the problem is simply quality of physical connection, the link continues and the bus driver starts a renegotiation, in which case a ERROR_NOT_READY is temporarily returned. When the link is stable and negotiated, communication continues without the need to reopen the device handle.

I would recommend adding a sleep statement of a second or two in between the instantiation of the USB printer, and the attempt to print to it. e.g:
from escpos.printer import Usb
from time import sleep
p = Usb(0x0456,0x0808)
sleep(1)
p.text('Hello World\n')

I get an error of traceback (most recent call last) when I try to run this Python program. I want to know the solution to this

This is a Python program to receive the data from an XBee module using the python-xBee library. I have installed both the xbee and pyserial modules.
import serial
from xbee import XBee
serial_port = serial.Serial('/dev/ttyUSB0', 9600)
xbee = XBee(serial_port)
while True:
try:
print xbee.wait_read_frame()
except KeyboardInterrupt:
break
serial_port.close()
But when I run this and any kind of program with serial port, this is the error I am getting:
Traceback (most recent call last):
File "C:/Users/Manurajeev/PycharmProjects/untitled/one.py", line 4, in
<module>
serial_port = serial.Serial('/dev/ttyUSB0', 9600)
File "C:\Python27\lib\site-packages\serial\serialwin32.py", line 31, in
__init__
super(Serial, self).__init__(*args, **kwargs)
File "C:\Python27\lib\site-packages\serial\serialutil.py", line 240, in
__init__
self.open()
File "C:\Python27\lib\site-packages\serial\serialwin32.py", line 62, in
open
raise SerialException("could not open port {!r}:
{!r}".format(self.portstr, ctypes.WinError()))
serial.serialutil.SerialException: could not open port '/dev/ttyUSB0':
WindowsError(3, 'The system cannot find the path specified.')
Process finished with exit code 1
I don't understand what the problem is. I tried everything, but the same error keeps popping up every time.

In Linux, check the permissions on the tty device (ls -l /dev/ttyUSB0) to ensure that you have read/write access to it. Note that it might have a different name.
For Windows, have you been able to open COM5 with a terminal emulator and send/receive data on the XBee? Do you still have it open in another program when you're trying to open it in Python? Only one program can access a COM port at a time.

How to read telnet sessions with python

Aloha, i'm creating a teamspeakbot and want to write and read to a telnet session created with a TeamSpeak3 server
import telnetlib
tn = telnetlib.Telnet('localhost', 10011, 10)
tn.read_all()
What i'm expecting:
Connected to localhost
Escape character is '^]'.
TS3
Welcome to the TeamSpeak 3 ServerQuery interface, type "help" for a li...
But instead i get a time out after the 10 seconds:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.7/telnetlib.py", line 325, in read_all
self.fill_rawq()
File "/usr/lib/python2.7/telnetlib.py", line 516, in fill_rawq
buf = self.sock.recv(50)
socket.timeout: timed out
How can i read all stuff the telnet connection tells me and later write some stuff to it (like the login proces and submit commands and get the response ...)
The Solution is
tn.read_very_eager()
My code now looks like this:
import telnetlib, time
tn = telnetlib.Telnet('localhost', 10011, 10)
tn.write('help\n')
time.sleep(0.05)
print(tn.read_very_eager())

read_all() blocks until EOF is reached*, or until your timeout is reached. While I've not used telnetlib much, I have assumed it's for the sort of service which displays something then closes the connection.
How do you get on with code like:
tn = telnetlib.Telnet('localhost', 10011, 10)
tn.read_some()
*https://docs.python.org/2/library/telnetlib.html#telnetlib.Telnet.read_all

Using numdisplay, "An existing connection was forced to close by the remote host"

I've been learning to use python in astronomy and for that I'm following this notes. In the very beginning the author does the following example:
>>> im = pyfits.getdata('http://das.sdss.org/www/cgi-bin/drC?RUN=3630&RERUN=40&CAMCOL=3&FIELD=83&FILTER=r')
>>> numdisplay.display(im,z1=1000,z2=1500)
I try to replicate it and I get:
>>> numdisplay.display(im,z1=1000,z2=1500)
Image displayed with Z1: 1000 Z2: 1500
Traceback (most recent call last):
File "<pyshell#13>", line 1, in <module>
numdisplay.display(im,z1=1000,z2=1500)
File "C:\Mine\Python\lib\site-packages\numdisplay\__init__.py", line 446, in display
_d.writeImage(bpix,_wcsinfo)
File "C:\Mine\Python\lib\site-packages\numdisplay\displaydev.py", line 513, in writeImage
self.writeData(_lx,_ydisp,_fpix[block,:])
File "C:\Mine\Python\lib\site-packages\numdisplay\displaydev.py", line 379, in writeData
self._writeHeader(opcode,self._MEMORY, -nbytes, x, y, frame, 0)
File "C:\Mine\Python\lib\site-packages\numdisplay\displaydev.py", line 542, in _writeHeader
self._write(a.tostring())
File "C:\Mine\Python\lib\site-packages\numdisplay\displaydev.py", line 580, in _write
nwritten = self._socket.send(s[-n:])
error: [Errno 10054] An existing connection was forced to close by the remote host
I don't understand what I'm doing wrong. I mean if I write numdisplay.open() everything is fine... I'm thinking that it might be my antivirus or something that doesn't let python to communicate with ds9... Can somebody help me?
Edit: Well it doesn't seem to be the antivirus. I stopped it and run the script and I got the same error.

I was getting similar error messages, and I just tried adding a non-'None' argument to the bufname argument and it works (my image is about 4096.4096):
numdisplay.display(data,bufname='imt4096')