DEVICE CLASSES

A device class is a scheme where user devices plugged into Energenie
product, can be referred to as objects within a user application.

It is a way of abstracting the on-air radio interface and Energenie
device specifics from a user application, such that the user can
code 'in the land of their devices'.


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REQUIREMENTS

1. EXPRESSIVE: To be able to write expressive and compact applications,
   that talk in the vocabulary of physical devices.

   a. All known Energenie devices to be modelled as classes inside a
      device database, and the capabilities and operations on those devices
      pre-written so they can be reused by a user application.

   b. An easy way for users to map energenie device intents to user
      device intents (such as by wrapping custom object vocabulary around
      the standard energenie device vocabulary) - e.g. room.heat() rather
      than plug.on()

  e.g. first level device names such as my_radiator or my_plug,
  or second level device names such as bedroom_radiator and kitchen_kettle
  (things plugged into devices)

  This will hide the detail of how messages get encoded and transported,
  and allows users to focus ore on the intents of the application, rather
  than the implementation details.


2. NAME REGISTRY: To be able to build a local registry of devices and their configurations,
   and refer to devices by name inside the application.

   a. to be configurable by learning (e.g. listen for messages such as
      a join message, and add the device to the registry)

   b. to be configurable by hand (e.g. hand entering the sensor id of
      a known device into the registry)

   c. to automatically build variables for the user program from the
      registry, so that users don't have to bother with lots of
      wiring up code every time their app starts.

   d. this registry must be persistable, e.g. save and restore to a disk file,
      so that on application startup, the device database is automatically loaded
      and objects created.

   e. the registry can be queried, such as 'find me all devices that are of
      type x' or 'find me all devices in location kitchen'.


3. INTENTS: To be able to command and query devices in a way that represents
   meaningful device-based intents (such as tv.on() and tv.get_power())

   a. received data values to be cached for deferred query, such as get_power()

   b. the last receipt time of data from a transmitting device to be known

   c. the next expected receipt time of data from a transmitting device to be known

   d. the last known state of a transmitting device to be known (e.g. switch state
      both by commanded state and retrieved state)


4. AGNOSTIC: To be able to refer to user devices in an Energenie device agnostic way.

   e.g. it doesn't matter if the TV is plugged into a green button device,
   or a MiHome device. It is always tv.on() in the code.


5. LEARN/DISCOVER: To be able to instigate and manage learn mode from within an app

   a. To send specific commands to green button devices so they can
      learn the pattern

   b. To sniff for any messages from MiHome devices and capture them
      for later analysis and turning into device objects

   c. To process MiHome join requests, and send MiHome join acks


6. ABSTRACTED RADIO: To completely hide the user from the on-air radio interface

   a. choosing the correct radio frequency and modulation automatically

   b. choosing the correct physical layer configuration automatically,
      such as message repeats for certain devices


Not as part of this work, but this should at least be enabled
by the design

7. PERFORMING: To be able to build a well performing system
   with very few message collisions and message losses

   a. by dynamically learning report patterns of MiHome devices

   b. by intelligently deferring and schedulling transmit messages
      to avoid transmit slots of reporting devices

   c. to query device characteristics such as modulation scheme and msg repeats.
      also to estimate the transmit time of a particular message to help
      with message scheduling.


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DESIGN Devices.py

  to have a device class for each supported Energenie product.

  These classes to define the operations on that device, such as on() off()
  get_power().

  Radio interface configuration parameters to be associated with each
  device class, such as the modulation scheme and message repeat requirements.

  commands modelled by function calls such as turn_on()

  commanded state? (did we ask it to be on, when did we ask?)
  reported state? (did it tell us it is on, when did we learn it?)

  overall device state
    can this device receive commands?
    can this device transmit reports?
    have we seen this device this run?
    when did we last hear from it?
    when did we last talk to it?
    when do we expect to next hear from it?

  common device features
    it's manufacturer id
    it's product id
    it's sensor id

  yet unmodelled devices still to be usable to some degree
    for MiHome devices, a proxy class generated dynamically based on received message parameters.
    e.g. if it reports a TEMPERATURE field, then there should be an automatic get_temperature() method
    generated.

  an incoming message callback
    this already knows it is for the device, but it is up to the device to decode and action

  an outgoing message sender
    to be knitted to the on air interface proxy, but no radio handler code in the device class or instance.

  TODO
    possibly add callbacks such as when_turned_on() when_turned_off() etc.

    Where do unknown incoming messages get routed to? Need to at least log them somewhere.
    Although they won't necessarily route to a device class. But useful for learning semantics.
    Perhaps there is a single 'UnknownDevice' that is just a Device() base class, that
    captures all of these messages? But there might be multiple devices, so perhaps
    we could generate UnknownDevice instances (optionally) when we receive messages
    from something that we don't know what it is yet?


(do we need to know what our last sent request is, vs last known reported state?
e.g. if we have sent a request but not heard a response yet, this means we think we asked
it to turn on, but we don't yet know if it has done that. Some devices can't report
back, but some can, so it would be nice to have a four stage state machine for on/off)

(note, would be good to be able to persist the last message received on disk,
so that when code restarts, it knows the last send/receive time that was last processed.
i.e. a resumable state machine persisted to disk)

(note, a message scheduler if inserted in the middle, would do callbacks to say
that the request has been processed, so timestamps can be updated. Also same scheduler
could handle retries perhaps, if the device is tx and rx, then when you send a switch
change, it would normally report back that the switch had changed, so if you don't
get it, or if it is in the wrong state, could retry a send again until it changes)

(note, inner variables might have two versions for some devices, the requested
value and the confirmed value. If they are different, it means might still be
waiting for a reply, so can't guarantee the command was received yet)

Device
  get_manufacturer_id
  get_sensor_id
  get_product_id

  (these may need an ack-back from radio module to know it happened)
  ?get_last_receive_time
  ?get_last_send_time
  ?get_next_receive_time
  ?get_next_send_time

  incoming_message (OOK or OpenThings as appropriate, stripped of header? pydict?)
  send_message (a link out to the transport, could be mocked, for example)

  EnergenieDevice
    get_radio_config -> config_selector? (freq, modulation) config_parameters? (inner_repeats, delay, outer_repeats)
    has_switch
    can_send
    can_receive

    LegacyDevice
      ENER002
        turn_on
        turn_off

    MiHomeDevice
      MIHO005 (AdaptorPlus)
        turn_on
        turn_off
        is_on
        is_off
        get_switch
        get_voltage
        get_freq
        get_apparent
        get_reactive
        get_real
      MIHO006 (HomeMonitor)
        get_battery_voltage
        get_current
      MIHO012 (eTRV)
        ?get_battery_voltage
        ?get_ambient_temperature
        ?get_pipe_temperature
        set_setpoint_temperature
        ?get_valve_position ?is_on ?is_off
        ?set_valve_position ?turn_on ?turn_off


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DESIGN Registry.py

file format? platform dependent database format, like dbm but there is
a platform dependent one - but need the licence to be MIT so we can
just embed it here to have zero dependencies.

persist the registry to disk and/or writeback new entries

load the registry from disk and/or parse it

add a device class instance to the registry with a friendly name
- could be from a discovery or learn process
- could be from a hand rolled object

get a device by name from the registry

delete a device from the registry

create a new device class instance from a name

auto-create variables in a given scope, for all persisted registry entries

list the registry in some printable format (like a configuration record)


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DESIGN - air_interface adaptors for FSK and OOK

It looks like we need an air_interface adaptor, that knits the device class
parents (LegacyDevice and MiHomeDevice) to the radio.

These adaptors will then OpenThings.encode() and OpenThings.decode() so that
the address can be consulted in the Registry.Router to route incoming messages
to the correct device class. This also then means that TwoBit.encode() must
be done in the air_interface adaptors, not in the Device class code.

There can be an air_interface adaptor for OOK and FSK, Both will take
payloads as pydict or tuple (ha, da, state) and encode/encrypt then
configure the radio for the right modulation and send it.

For the receive pipeline, a message pump somewhere in the main loop has to
put the radio into receive OOK or receive FSK, then when a payload comes in,
passes up to the appropriate air_interface. The FSK air_interface adaptor
knows to OpenThings.decode before sending to the fsk_router, which then routes
to the right device class instance.

Similarly, an OOK transmit in the air_interface adaptor knows to TwoBit.encode
the tuple (ha, da, s), configure the radio modulation to OOK, pass on any
device specific parameters such as inner_repeats, and then transmit the message.


When we introduce a message scheduler, it will be at the air_interface
layer, and sending and receiving will be deferred on a queue and scheduled,
rather than handled immediately.

Note: message send and receipt times will have to be relayed to the device classes,
either by parameter, or at time of receipt by the class. The scheduler will need
to precisely know the receipt time to do accurate scheduling, but the device class
probably only needs to know actual receipt time in the class for freshness measurement
reasons.


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DESIGN NOTES - registry data store

REQUIREMENT: I want a simple persistent kvp database with the following features:

1. A file format that is portable across all platforms

   so that a single registry file could be copied from a tutorial onto
   any machine and it would just work

2. A file format that is human readable and easily editable

   so that users could create or edit the file just like a config file

3. A simple read and write key/value abstraction in python
   with a full CRUD lifecycle

   so that new kvp's can be created, read, updated and deleted.

4. Doesn't have to be hugely efficient or store very large data sets

   it's mostly used for configuration data that rarely changes,
   or last known values that tend to be quite small.

5. MIT licence

   so that it can be just embedded in an existing project

6. A single python file

   so it is easy to embed

7. Works out of the box with no changes on Python 2 and Python 3

   so it doesn't have to be configured or changed and does not limit
   or dictate a specific python version.

Additionally, it might:

8. A option to add multi process locking later if required, but not
   included by default

   so that it could be used as a simple central database for multiple
   programs sharing the same data set.

9. understand read only and read/write intents better

   when using configuration data and last known values, it is useful
   to keep them in the same single file, so it is easy to copy
   to other machines. Some data is naturally 'write once' and
   very configuration based. Some data is naturally 'write often'.
   It might be nice if these two types of data could appear in the same
   file, but the locking/performance and resilience issues be handled
   differently for the two classes of data - e.g. perhaps having
   two connections to the same database file, one in read only mode
   for config records, and one in read/write mode for last use data.
   There might also be different namespace prefixes in the file
   so that the key sets are separate, or there may be a way to
   link them so that when you read a record you get both the static
   config data and the fast changing last use data as a single
   record. But this then implies when you do an update, you
   probably want to update part of a record rather than the
   whole record.


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DESIGN NOTES - discovery process

a way to sequence transmit messages to allow legacy devices to learn a code.

a way to listen (for a long time) for any devices that transmit, and add them
(optionally?) to the device registry.

a way to listen (in the background) during normal operation for unknown devices,
and optionally add them to the device registry.


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GENERAL NOTES

(when configuring the system)
print("Press the learn button on the TV device")
energenie.start_learn(house_code=0xABCDE, index=2)
raw_input("Press enter when done")
energenie.stop_learn()

energenie.create_device("tv", energenie.device.ENER002, index=2, house_code=0xABCDE)
energenie.create_device("aquarium", energenie.device.MIHO005, address=0x1234)

(when running the system)

tv = energenie.get("tv")
aquarium = energenie.get("aquarium")

tv.off()
aquarium.on()
time.sleep(10)
if aquarium.power > 20:
print("Has the pump motor stalled??")

def just_turned_off(device):
print("Your user just turned off %s" % device)
print("I'm turning it back on!")
device.on()

aquarium.when_turned_off(just_turned_off)


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END