Read data from an IOC

This guide explains how to read data from an IOC in a separate Python program.

Note

Please ensure your firewall allows both TCP and UDP traffic on ports 5064 and 5065. These are used by EPICS for channel access to the PVs.

To start, run the cothread IOC from Creating an IOC or the asyncio IOC from Use asyncio in an IOC and leave it running at the interactive shell.

We will read data from that IOC using this script:

from softioc import softioc
from cothread.catools import caget, caput, camonitor

print(caget("MY-DEVICE-PREFIX:AI"))
print(caget("MY-DEVICE-PREFIX:AO"))
print(caput("MY-DEVICE-PREFIX:AO", "999"))
print(caget("MY-DEVICE-PREFIX:AO"))

softioc.interactive_ioc(globals())

Note

You may see warnings regarding the missing “caRepeater” program. This is an EPICS tool that is used to track when PVs start and stop. It is not required for this simple example, and so the warning can be ignored.

From the interactive command line you can now use the caget and caput functions to operate on the PVs exposed in the IOC. Another interesting command to try is:

camonitor("MY-DEVICE-PREFIX:AI", lambda val: print(val))

You should observe the value of AI being printed out, once per second, every time the PV value updates.