• all controlled by bluesky
• multiple scan variables can be controlled either by controls and/or daq
  • variables could be drp parameters
• option 1 (preferred for uniformity): all scan variables made visible in epics where possible
  • issue: feels like this could be awkward for daq: need another thread/process watching epics.  maybe device doesn't permit separate configure/data processes (e.g. if they share same pgp virtual channel)
• option 2: scan variable not epics and is a daq var controlled by a daq executable participating in transitions:
  • transmit configUpdate json on zmq phase of transition
  • json specifies which detector is responsible (e.g. xpphsd) for updating scan var, and an epics variable to set when complete
  • that daq executable must understand that json and record it to xtc configUpdate transition
• at configure time: bluesky hands json describing the scan (names, initial values) to the scanning node(s) which are translated to xtc by json2xtc
• at configUpdate time: get similar json just with updated values
• this json is distributed on first phase of configUpdate transition
• who receives this scan info?
• how does the daq tell bluesky if its scan var is ready to go?
• configUpdate transition goes through the timing system with usual two phase pattern
• ami only moves forward in time.  for arrays only have to update dgram (since python-config points to arrays) while for numbers/charstr/enum have to update both dgram and python-config
  • issue: dgrams are read-only

...

rule for the docstring? "detname_scanname_step"
scanname "chargeinj7" means every 7th pixel
scanname "chargeinj3" means every 3rd pixel

step_value = 0
step_docstring = "epix0_chargeinj_0; epix3_chargeinj_0; epix7_chargeinj_0"

step_value = 1
step_docstring = "epix0_chargeinj_1; epix3_chargeinj_1; epix7_chargeinj_1"

Psana Step-Store Approach

The idea here is tomake the bluesky scans look the same as det-config scans.  Mona’s step-store (from “detnames -s”) contains a list of variables, which in both cases includes step_value, step_docstring ("metadata").  In the case of a bluesky scan it also includes the PV values.  In the case of a config scan the configs themselves get updated on each step.