Rework scan_info acquisition_chain

This is proposal to discuss about reworking the acquisition_chain field from the scan_info.

State

Now the acquisition_chain looks like that:

    "acquisition_chain": {
        "timer": {
            "master": {
                "images": [],
                "scalars": ["timer:elapsed_time", "timer:epoch"],
                "spectra": [],
            },
            "scalars": ["diode1"],
            "images": ["lima1:image"]
        },
        "axis":
            "master": {
                "images": [],
                "scalars": ["sx"],
                "spectra": [],
            },
            "scalars": ["diode2"],
        "img": {
            "master": {
                "images": ["lima2:image"],
            },
            "spectra": ["opium:mca1"],
            "scalars": ["timer:elapsed_time", "timer:epoch"]
        },
    },

It contains:

• Relationship between top master and channels
• Channel generated by device used as master
• Kind of channel data
• Ordered top masters
• Ordered channels

What i don't like

• 1. structurally is_master and data kind are orthogonal information
  • but here is handled by combination (6*2 = 6 lists, for now)
• 2. data kind have nothing to do with the acquisition_chain
  • This information is probably not at the proper place
• 3. spectra is not a proper name for any kind of list of values (in fact it's the same for image)
  • It feels like an accurate kind, but it's just about data dimension
• 4. A channel is never a master -> a device is the master and this device produce a channel
  • What does lima:image as master means?
    • That's in fact just a counter
  • Maybe there is a better way to handle that
• 5. We have to expose metadata per devices (right now we have to cheat using channels)

Proposal 1

• This address 1) 2) 3)
• Now we have a scan_info/channels fields which can be used for data kind
• We can use data dim instead of data kind

scan_info = {
    'acquisition_chain': {
        'timer': {
            # WAS ADDED
            'devices': ['timer', 'simulation_diode_sampling_controller'],

            # STILL THERE FOR COMPATIBILITY
            'images': [],                                                                                                                                                      
            'master': {'images': [], 'scalars': ['timer:elapsed_time', 'timer:epoch'], 'spectra': []},
            'scalars': ['simulation_diode_sampling_controller:diode1'],
            'spectra': []}
    },

    # WAS ADDED
    'devices': {
        'simulation_diode_sampling_controller': {
            'channels': ['simulation_diode_sampling_controller:diode1']},
        'timer': {
            'channels': ['timer:elapsed_time', 'timer:epoch'],                                                                                                                           
            'triggers': ['simulation_diode_sampling_controller']}
    },

    'channels': {
        'simulation_diode_sampling_controller:diode1': {
            'dim': 0,  # <-- DIM WAS ADDED
            'display_name': 'diode1'},
        'timer:elapsed_time': {
            'dim': 0,
            'display_name': 'elapsed_time',
            'unit': 's'},                                                                                                                                                  
        'timer:epoch': {
            'dim': 0,
            'display_name': 'epoch',
            'unit': 's'}
    },
}

It contains the same information as before then I think there is no problem to implement this change.

Proposal 1+1

• This address 4) 5)
• We can expose the devices and the relationshit between devices and channels
• A device can be a master if it triggers other devices (no magic, exact same model as bliss)

    'acquisition_chain': {
        'timer': {
            # WAS ADDED
            'devices': ['timer', 'simulation_diode_sampling_controller'],

            # STILL THERE FOR COMPATIBILITY
            'images': [],                                                                                                                                                      
            'master': {'images': [], 'scalars': ['timer:elapsed_time', 'timer:epoch'], 'spectra': []},
            'scalars': ['simulation_diode_sampling_controller:diode1'],
            'spectra': []}
    },

    # WAS ADDED
    'devices': {
        'simulation_diode_sampling_controller': {
            'channels': ['simulation_diode_sampling_controller:diode1']},
        'timer': {
            'channels': ['timer:elapsed_time', 'timer:epoch'],                                                                                                                           
            'triggers': ['simulation_diode_sampling_controller']}
    },