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CaChannel¶
Summary¶
Describes how to use the CaChannel package to connect to an instrument that uses the EPICS software control suite.
Installation¶
The installation of the CaChannel depends on how you have installed mantid.
See https://www.mantidproject.org/installation the available methods.
Developers should use the Conda Package method
Full Installation¶
If you installed mantid via an installer package then simplest way to install CaChannel is to run the following script in the Workbench Script Window
"""Install CaChannel with pip"""
import subprocess as subp
import sys
# Run pip using the same executable as the running Python
py_exe = sys.executable
pip_cmd = (
py_exe, "-m", "pip", "install", "--upgrade-strategy", "only-if-needed", "cachannel"
)
process = subp.run(pip_cmd, stdout=subp.PIPE, stderr=subp.STDOUT, encoding="utf-8")
print(process.stdout)
process.check_returncode()
Conda Package¶
If you installed mantid via Conda then you can add CaChannel to your existing environment:
>conda activate your-environment-name
>const install --channel paulscherrerinstitute cachannel
Usage¶
Assuming the instrument can be contacted by a prefix PREFIX1:PREFIX2 then to retrieve a process variable you would type the following Python code:
from CaChannel import CaChannel, CaChannelException, ca
chan = CaChannel('PREFIX1:PREFIX2:PVNAME:VALUENAME')
chan.setTimeout(5.0)
chan.searchw()
as_string=True # set to False if you want a numeric value
print(chan.getw(ca.DBR_STRING if as_string else None))
where PVNAME:VALUENAME is the name of the PV variable and associated value.
The print statement should print the text value of the PV.
If no output is returned then the connection could not be made.
Check the IP address of the server is in the environment variable above and that the full name of the PV is correct.
Example PV names for INTER:
IN:INTER:DAE:TITLE
IN:INTER:DAE:RUNNUMBER
IN:INTER:CS:SB:Theta
IN:INTER:CS:SB:S1VG