Sparrow Object Model

#The Sparrow Object Model The object model allow any IoT device describe itself via a set of object instances (similar to LWM2M). Any IoT device have one to N-instances and the first instance (called instance zero) is used for discovery of the device / product type and for device management.

Each object defines a number of variables. Some are common with all Sparrow objects others are specific for the object type. Some of the common variables are for discovery and are listed below:

• Product/Object Type (0x00) - the object type (64-bit) - for instance zero it is a product type for other instances it is the object type.
• Device Id (0x01) - only used in instance zero where it is defining the device ID (128-bit).
• Object label (0x02) - a string describing the object
• Number of instances (0x03)- only valid for instance zero - number of object instances in this IoT device

Other variables are specific for the object they are in - such as these from the LEDs instance:

• Number of LEDs (0x100) - gets the number of LEDs that can be controlled via this object instance
• LED control (0x101) - control the state of the LEDs
• LED set (0x102) - set the specific LED to on
• LED clear (0x103) - set the specific LED to off

The specific variables start at 0x100 while the discovery variables are between 0x00 and 0xC0. There are also a set of variables specifically for instance zero - that are used for device management - these are the ones between 0xc0 and 0x100.

Sparrow Devices and Discovery

A Sparrow IoT device have at least one instance - the instance zero. Using the Sparrow protocol (Encap and TLV) it is possible to discover what type of device it is and which object instance it implements. The Zolertia Re-mote example device have the following instances:

• Instance Zero with product ID: XYZ.
• Instance 1 with object ID: xxx-yyy (Flash instance) - primary image
• Instance 2 with object ID: xxx-yyy (Flash instance) - secondary image
• Instance 3 with object ID: xxx-yyy.

Running the discovery tool on it will show the following output:

 >tlvdiscovery.py
 >...

Sparrow ID range

Sparrow make use of EUI-64 ID for all the object types and also image types. This means that anyone that owns a OUI ID range can create their own non-overlapping object IDs. SICS have a ID range defined 70-B3-D5-70-5 and using this EUI-64 can be defined like:

70-B3-D5-70-5X-<24-bit ID>

Where the 24-bit ID is defining the type of the object and the prefix ensures that it is globally unique so that there is no need for having a registry for objects. The whole 64-bit identifier is read out in the discovery to identify which object it is that all the instances implement.

1. Image type - for firmware images to ensure that only correct image types are uploaded to a specific device
2. Object type - any functional object such as temperature sensor object, lamp object, etc.
3. Product type - any type of product such as a Zolertia Re-mote or Yanzi LED Lamp