The timeStampFifo module handles registering the asyn timeStampSource automatically
in an aSub record that takes the port name PV as one of it's arguments.

To use timeStampFifo, set TIMESTAMPFIFO in your configure/RELEASE* file(s) to add it to your build.

In your *App/Db/Makefile, add a line like this:
DB_INSTALLS += $(TIMESTAMPFIFO)/db/timeStampFifo.template

In your *App/src/Makefile, add lines like these:
$(PROD_NAME)_DBD += timeStampFifo.dbd
$(PROD_NAME)_LIBS += timeStampFifo

In your st.cmd files, load the timeStampFifo.template records like this:
# Load timestamp plugin
dbLoadRecords("db/timeStampFifo.template",  "DEV=$(CAM_PV):TSS,PORT_PV=$(CAM_PV):PortName_RBV,EC_PV=$(CAM_PV):BeamEventCode_RBV,DLY_PV=$(CAM_PV):TrigToTS_Calc NMS CPP" )

where
DEV		= Prefix for the timeStampFifo PVs
PORT_PV	= PV name where the asyn port name can be fetched
EC_PV	= PV name where the event code can be fetched.  For LCLS2 the event code is the channel event, i.e. 1000 + trigger channel number
DLY_PV	= PV name where the estimated trigger to timestamp delay can be fetched

In the example above the DLY_PV is $(CAM_PV):TrigToTS_Calc which is already
provided in the ADAndor, ADEdtPdv, ADProsilica, ADVimba, and aravisGigE modules.

The timeStampFifo module has a debug variable that can help diagnose problems, DEBUG_TS_FIFO.
Default is 1 which just shows some startup msgs.
Set to 2 for some additional diags, and higher numbers for more diags.

If I have a new camera that I'm just setting up for timeStampFifo
I'll set the areaDetector $(CAM_PV):ImageMode to Multiple,
$(CAM_PV):NumImages to 5, and DEBUG_TS_FIFO to 15.

That produces lots of diagnostics for 5 images and stops so you can look at what happened.