V4 Use Cases

Overview

These are example use cases where we need to assert that each layer of EPICS V4 handles them:

1. Can the CA client user API articulate the request?

2. Can the network protocol transfer the request?

3. Do the database & drivers understand the request and provide the necessary data?

4. Does the data get back up to the client in the appropriate form and at the requested time?

Use Cases

Command-line tools for debugging and scripting

1. Dump the current "value" property of the channel "fred".

2. Dump all properties, their type, and current value for a given channel.

3. Dump the timestamp, value, units, status, severity of "fred" once a second.

4. ... whenever any of the timestamp, ... severity change.

5. List all events that a PV supports: On change, 1Hz, RF Pulse, Beam Pulse, ...

6. Dump the value of the cavity waveform for every beam pulse.

7. List all channels that match a given name pattern.

Display Manager

1. Display an analog input value on a bar:
Get limits, subscribe to values, receive value & display it, receive change-of-display-range notification,...

2. Display a menu output for a 2 state valve on a text update:
Get state strings, subscribe to (numeric?) value, display incoming data, receive state string updates, ...

3. Give a controller for a 2 state valve controller on a radio button.
Handle same as 2?

4. Display a waveform on an xy plot.
Similar to 1, but array data?

5. Attempt to display a string on a bar

6. Universal PV Inspector:
Get properties, allow user to select properties.
If writeable string -> display text entry field.
If read-only string -> display text update field.
If writeable numeric with limits -> display slider with range of number.
....

7. Display as bars, a list of BPMs where I can set the offset in time to fetch (assuming that these BPMs are read as arrays that are all triggered at one time – but I want to see them at different points in time as it goes down the beamline).

Physics Application

BPM-related ideas

1. List all channels available that are BPMs

2. Select all of them in sector 6

3. Display them when the beam is going to the end station A (one of 8 destinations possible)

4. Same, but display all BPMs on the .1 Hz event

  Scan a probe in the beam line

1. Find PVs for some beam line device:
Stepper motors for probe's X & Y position, intensity of beam transmitted by probe, beam shutter open/close, beam available

2. Scan sequence:

Assert shutter is closed;
move X/Y to 0/0, wait for completion
until done:
   open shutter, wait until open
   measure intensity for 1 second while beam_available
   close shutter
   move to next position, wait until you get there

Archiver

1. Get value, timestamp, status/severity of a channel once per second

2. Archive default properties of a channel using the default deadband.
How are they defined? How does the archiver learn about them?

3. Given that there is a new view defined in the stepper motor that includes all motor readback data:Subscribe to counterClockWiseLimit, clockWiseLimit, moving, doneRetries, homeLimit at 10 Hz.