This is an EPICS relay server written in python using the pcaspy library. You can send data using an EPICS client, e.g. pyepics, to a not yet existing process variable (PV) which fits the naming rules (prefix & dtype-suffix). A PV will then be created on the fly for other clients to read from. camonitor will work as normal, tough the PV has to exist prior to a camonitor call.
There is no implementation for setting limits, units or other higher order PV-attributes ...yet. Only type (int, float, char) and count. And, because I needed it, a right appending buffer.
EPICS based control systems don't need relays or brokers for communication, so why would you need a relay? It's a really easy way to publish variables from anywhere as PVs without building a server around them. Every script or service you run that doesn't need any input can push data via caput to the relay to make available instead of building a server around it.
The relay server starts with an empty PV list. New PVs can be created during run-time by putting a value to the server using the correct syntax:
<prefix>:<name>_<dtype><count>
e.g.
epics.put("5trap:relay:cupsofcoffeetoday_i1", 2)
epics.put("5trap:relay:temperature_lab_f1", 21.2)
epics.put("5trap:relay:fit_results_f4", [23.0, 0.1, 3231.123, 1e-4])
epics.put("5trap:relay:pressure_log_F100", 1e-4) # this is a buffer of length 100. Values put will be appended right.
epics.put("5trap:relay:cmdline_output_c10000", "The sun is shining, go outside!")The prefix is the server identifier, the name is an arbitray name for you to choose to describe the variable. dtype defines the value type (float, int, char, Upper case letters for a buffer) and count gives the number of elements in this PVs array.
- Change the way the server class accesses the driver. Its using the global variable defined in if name==main and thats just not pretty.
- Add some method to adjust units, alarm limits and other PV attributes.
- Autosave current PV names (and values?) to recreate the PVs on server restart. That would help with camonitoring startups after system failures.
- Menno Door - Initial work - door at mpi-k.de
This project is licensed under the MIT License - see the LICENSE.md file for details