Master Driver Agent

The Master Driver Agent manages all device communication. To communicate with devices you must setup and deploy the Master Driver Agent. For more information on the Master Driver Agent’s operations, read about the Master Driver in the driver framework docs.

Configuring the Master Driver

Configuration for each device consists of 3 parts:

  • Master Driver Agent configuration file - lists all driver configuration files to load
  • Driver configuration file - contains the general driver configuration and device settings
  • Device Register configuration file - contains the settings for each individual data point on the device

For each device, you must create a driver configuration file, device register configuration file, and an entry in the Master Driver Agent configuration file.

Once configured, the Master Driver Agent is configured and deployed in a manner similar to any other agent:

python scripts/install-agent.py -s services/core/MasterDriverAgent -c <master driver config file>

Requirements

VOLTTRON drivers operated by the master driver may have additional requirements for installation. Required libraries:

BACnet driver - bacpypes
Modbus driver - pymodbus
Modbus_TK driver - modbus-tk
DNP3 and IEEE 2030.5 drivers - pydnp3

The easiest way to install the requirements for drivers included in the VOLTTRON repository is to use bootstrap.py (see platform installation for more detail)

Master Driver Agent Configuration

The Master Driver Agent configuration consists of general settings for all devices. The default values of the Master Driver should be sufficient for most users. The user may optionally change the interval between device scrapes with the driver_scrape_interval.

The following example sets the driver_scrape_interval to 0.05 seconds or 20 devices per second:

{
    "driver_scrape_interval": 0.05,
    "publish_breadth_first_all": false,
    "publish_depth_first": false,
    "publish_breadth_first": false,
    "publish_depth_first_all": true,
    "group_offset_interval": 0.0
}
  • driver_scrape_interval - Sets the interval between devices scrapes. Defaults to 0.02 or 50 devices per second. Useful for when the platform scrapes too many devices at once resulting in failed scrapes.
  • group_offset_interval - Sets the interval between when groups of devices are scraped. Has no effect if all devices are in the same group.

In order to improve the scalability of the platform unneeded device state publishes for all devices can be turned off. All of the following setting are optional and default to True.

  • publish_depth_first_all - Enable “depth first” publish of all points to a single topic for all devices.
  • publish_breadth_first_all - Enable “breadth first” publish of all points to a single topic for all devices.
  • publish_depth_first - Enable “depth first” device state publishes for each register on the device for all devices.
  • publish_breadth_first - Enable “breadth first” device state publishes for each register on the device for all devices.

An example master driver configuration file can be found in the VOLTTRON repository in services/core/MasterDriverAgent/master-driver.agent.

Driver Configuration File

Note

The terms register and point are used interchangeably in the documentation and in the configuration setting names. They have the same meaning in the context of VOLTTRON drivers.

Each device configuration has the following form:

{
    "driver_config": {"device_address": "10.1.1.5",
                      "device_id": 500},
    "driver_type": "bacnet",
    "registry_config":"config://registry_configs/vav.csv",
    "interval": 60,
    "heart_beat_point": "heartbeat",
    "group": 0
}

The following settings are required for all device configurations:

  • driver_config - Driver specific setting go here. See below for driver specific settings.
  • driver_type - Type of driver to use for this device: bacnet, modbus, fake, etc.
  • registry_config - Reference to a configuration file in the configuration store for registers on the device. See the Registry-Configuration-File section below or and the Adding Device Configurations to the Configuration Store section in the driver framework docs.

These settings are optional:

  • interval - Period which to scrape the device and publish the results in seconds. Defaults to 60 seconds.
  • heart_beat_point - A Point which to toggle to indicate a heartbeat to the device. A point with this Volttron Point Name must exist in the registry. If this setting is missing the driver will not send a heart beat signal to the device. Heart beats are triggered by the Actuator Agent which must be running to use this feature.
  • group - Group this device belongs to. Defaults to 0

These settings are used to create the topic that this device will be referenced by following the VOLTTRON convention of {campus}/{building}/{unit}. This will also be the topic published on, when the device is periodically scraped for it’s current state.

The topic used to reference the device is derived from the name of the device configuration in the store. See the Adding Device Configurations to the Configuration Store section of the driver framework docs.

Device Grouping

Devices may be placed into groups to separate them logically when they are scraped. This is done by setting the group in the device configuration. group is a number greater than or equal to 0. Only number of devices in the same group and the group_offset_interval are considered when determining when to scrape a device.

This is useful in two cases:

  • If you need to ensure that certain devices are scraped in close proximity to each other you can put them in their own group. If this causes devices to be scraped too quickly the groups can be separated out time wise using the group_offset_interval setting.
  • You may scrape devices on different networks in parallel for performance. For instance BACnet devices behind a single MSTP router need to be scraped slowly and serially, but devices behind different routers may be scraped in parallel. Grouping devices by router will do this automatically.

The group_offset_interval is applied by multiplying it by the group number. If you intend to use group_offset_interval only use consecutive group values that start with 0.

Registry Configuration File

Registry configuration files setup each individual point on a device. Typically this file will be in CSV format, but the exact format is driver specific. See the section for a particular driver for the registry configuration format.

The following is a simple example of a Modbus registry configuration file:

Catalyst 371
Reference Point Name Volttron Point Name Units Units Details Modbus Register Writable Point Address Default Value Notes
CO2Sensor ReturnAirCO2 PPM 0.00-2000.00 >f FALSE 1001   CO2 Reading 0.00-2000.0 ppm
CO2Stpt ReturnAirCO2Stpt PPM 1000.00 (default) >f TRUE 1011 1000 Setpoint to enable demand control ventilation
HeatCall2 HeatCall2 On / Off on/off BOOL FALSE 1114   Status indicator of heating stage 2 need

Device State Publishes

By default, the value of each register on a device is published 4 different ways when the device state is published. Consider the following settings in a driver configuration stored under the name devices/pnnl/isb1/vav1:

{
    "driver_config": {"device_address": "10.1.1.5",
                      "device_id": 500},

    "driver_type": "bacnet",
    "registry_config":"config://registry_configs/vav.csv",
}

In the vav.csv file is a register with the name temperature. For these examples the current value of the register on the device happens to be 75.2 and the meta data is

{"units": "F"}

When the driver publishes the device state the following 2 things will be published for this register:

A “depth first” publish to the topic devices/pnnl/isb1/vav1/temperature with the following message:

[75.2, {"units": "F"}]

A “breadth first” publish to the topic devices/temperature/vav1/isb1/pnnl with the following message:

[75.2, {"units": "F"}]

These publishes can be turned off by setting publish_depth_first and publish_breadth_first to false respectively.

Also these two publishes happen once for all registers:

A “depth first” publish to the topic devices/pnnl/isb1/vav1/all with the following message:

[{"temperature": 75.2, ...}, {"temperature":{"units": "F"}, ...}]

A “breadth first” publish to the topic devices/all/vav1/isb1/pnnl with the following message:

[{"temperature": 75.2, ...}, {"temperature":{"units": "F"}, ...}]

These publishes can be turned off by setting publish_depth_first_all and publish_breadth_first_all to false respectively.

Device Scalability Settings

In order to improve the scalability of the platform unneeded device state publishes for a device can be turned off. All of the following setting are optional and will override the value set in the main master driver configuration.

  • publish_depth_first_all - Enable “depth first” publish of all points to a single topic.
  • publish_breadth_first_all - Enable “breadth first” publish of all points to a single topic.
  • publish_depth_first - Enable “depth first” device state publishes for each register on the device.
  • publish_breadth_first - Enable “breadth first” device state publishes for each register on the device.

It is common practice to set publish_breadth_first_all, publish_depth_first, and publish_breadth_first to False unless they are specifically needed by an agent running on the platform.

Note

All Historian Agents require publish_depth_first_all to be set to True in order to capture data.

Master Driver Override

By default, every user is allowed write access to the devices by the master driver. The override feature will allow the user (for example, building administrator) to override this default behavior and enable the user to lock the write access on the devices for a specified duration of time or indefinitely.

Set Override On

The Master Driver’s set_override_on RPC method can be used to set the override condition for all drivers with topic matching the provided pattern. This can be specific devices, groups of devices, or even all configured devices. The pattern matching is based on bash style filename matching semantics.

Parameters:

  • pattern: Override pattern to be applied. For example,
    • If the pattern is campus/building1/* the override condition is applied for all the devices under campus/building1/.
    • If the pattern is campus/building1/ahu1 the override condition is applied for only the campus/building1/ahu1 device. The pattern matching is based on bash style filename matching semantics.
  • duration: Time duration for the override in seconds. If duration <= 0.0, it implies an indefinite duration.
  • failsafe_revert: Flag to indicate if all the devices falling under the override condition has to be set to its default state/value immediately.
  • staggered_revert: If this flag is set, reverting of devices will be staggered.

Example set_override_on RPC call:

self.vip.rpc.call(PLATFORM_DRIVER, "set_override_on", <override pattern>, <override duration>)

Set Override Off

The override condition can also be toggled off based on a provided pattern using the Master Driver’s set_override_off RPC call.

Parameters:

  • pattern: Override pattern to be applied. For example,
    • If the pattern is campus/building1/* the override condition is removed for all the devices under campus/building1/.
    • If the pattern is campus/building1/ahu1 the override condition is removed for only for the campus/building1/ahu1 device. The pattern matching is based on bash style filename matching semantics.

Example set_override_off RPC call:

self.vip.rpc.call(PLATFORM_DRIVER, "set_override_off", <override pattern>)

Get Override Devices

A list of all overridden devices can be obtained with the Master Driver’s get_override_devices RPC call.

This method call has no additional parameters.

Example get_override_devices RPC call:

self.vip.rpc.call(PLATFORM_DRIVER, "get_override_devices")

Get Override Patterns

A list of all patterns which have been requested for override can be obtained with the Master Driver’s get_override_patterns RPC call.

This method call has no additional parameters

Example “get_override_patterns” RPC call:

self.vip.rpc.call(PLATFORM_DRIVER, "get_override_patterns")

Clear Overrides

All overrides set by RPC calls described above can be toggled off at using a single clear_overrides RPC call.

This method call has no additional parameters

Example “clear_overrides” RPC call:

self.vip.rpc.call(PLATFORM_DRIVER, "clear_overrides")

For more information, view the Global Override Specification