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IO Connector Plugin

Version: 1.0

Status: ⚫⚫⚫

IOConnector plugin for Thunder framework.

Table of Contents

Introduction

Scope

This document describes purpose and functionality of the IOConnector plugin. It includes detailed specification about its configuration, methods and properties as well as sent notifications.

Case Sensitivity

All identifiers of the interfaces described in this document are case-sensitive. Thus, unless stated otherwise, all keywords, entities, properties, relations and actions should be treated as such.

Acronyms, Abbreviations and Terms

The table below provides and overview of acronyms used in this document and their definitions.

Acronym Description
API Application Programming Interface
GPIO General-Purpose Input/Output
HTTP Hypertext Transfer Protocol
JSON JavaScript Object Notation; a data interchange format
JSON-RPC A remote procedure call protocol encoded in JSON

The table below provides and overview of terms and abbreviations used in this document and their definitions.

Term Description
callsign The name given to an instance of a plugin. One plugin can be instantiated multiple times, but each instance the instance name, callsign, must be unique.

References

Ref ID Description
HTTP HTTP specification
JSON-RPC JSON-RPC 2.0 specification
JSON JSON specification
Thunder Thunder API Reference

Description

The IO Connector plugin provides access to GPIO pins.

The plugin is designed to be loaded and executed within the Thunder framework. For more information about the framework refer to [Thunder].

Configuration

The table below lists configuration options of the plugin.

Name Type M/O Description
callsign string mandatory Plugin instance name (default: IOConnector)
classname string mandatory Class name: IOConnector
locator string mandatory Library name: libWPEIOConnector.so
startmode string mandatory Determines in which state the plugin should be moved to at startup of the framework
pins array mandatory List of GPIO pins available on the system
pins[#] object mandatory Pin properties
pins[#].id integer mandatory Pin ID
pins[#].mode string mandatory Pin mode (must be one of the following: Active, Both, High, Inactive, Low, Output)
pins[#]?.activelow boolean optional Denotes if pin is active in low state (default: false)

Interfaces

This plugin implements the following interfaces:

This interface uses legacy lowercase naming convention. With the next major release the naming convention will change to camelCase.

Methods

The following methods are provided by the IOConnector plugin:

Built-in methods:

Method Description
versions Retrieves a list of JSON-RPC interfaces offered by this service
exists Checks if a JSON-RPC method or property exists
register Registers for an asynchronous JSON-RPC notification
unregister Unregisters from an asynchronous JSON-RPC notification

versions method

Retrieves a list of JSON-RPC interfaces offered by this service.

Parameters

This method takes no parameters.

Result

Name Type M/O Description
result array mandatory A list ofsinterfaces with their version numbers
Array length must be at most 255 elements.
result[#] object mandatory ...
result[#].name string mandatory Name of the interface
result[#].major integer mandatory Major part of version number
result[#].minor integer mandatory Minor part of version number
result[#].patch integer mandatory Patch part of version version number

Example

Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "IOConnector.1.versions"
}

Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": [
    {
      "name": "JMyInterface",
      "major": 1,
      "minor": 0,
      "patch": 0
    }
  ]
}

exists method

Checks if a JSON-RPC method or property exists.

Description

This method will return True for the following methods/properties: pin, versions, exists, register, unregister.

Parameters

Name Type M/O Description
params object mandatory ...
params.method string mandatory Name of the method or property to look up

Result

Name Type M/O Description
result boolean mandatory Denotes if the method exists or not

Example

Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "IOConnector.1.exists",
  "params": {
    "method": "pin"
  }
}

Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": false
}

register method

Registers for an asynchronous JSON-RPC notification.

Description

This method supports the following event names: activity.

Parameters

Name Type M/O Description
params object mandatory ...
params.event string mandatory Name of the notification to register for
params.id string mandatory Client identifier

Result

Name Type M/O Description
result null mandatory Always null

Errors

Message Description
ERROR_FAILED_REGISTERED Failed to register for the notification (e.g. already registered)

Example

Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "IOConnector.1.register",
  "params": {
    "event": "activity",
    "id": "myapp"
  }
}

Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": null
}

unregister method

Unregisters from an asynchronous JSON-RPC notification.

Description

This method supports the following event names: activity.

Parameters

Name Type M/O Description
params object mandatory ...
params.event string mandatory Name of the notification to register for
params.id string mandatory Client identifier

Result

Name Type M/O Description
result null mandatory Always null

Errors

Message Description
ERROR_FAILED_UNREGISTERED Failed to unregister from the notification (e.g. not yet registered)

Example

Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "IOConnector.1.unregister",
  "params": {
    "event": "activity",
    "id": "myapp"
  }
}

Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": null
}

Properties

The following properties are provided by the IOConnector plugin:

IOConnector interface properties:

Property R/W Description
pin read/write GPIO pin value

pin property

Provides access to the GPIO pin value.

The id parameter shall be passed as the index to the property, i.e. pin@<id>.

Index

Name Type M/O Description
id integer mandatory Pin ID

Value

Name Type M/O Description
(property) object mandatory GPIO pin value
(property).value integer mandatory Value of the pin
Name Type M/O Description
(property) integer mandatory GPIO pin value

Errors

Message Description
ERROR_UNKNOWN_KEY Unknown pin ID given

Example

Get Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "IOConnector.1.pin@189"
}

Get Response

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": 0
}

Set Request

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "IOConnector.1.pin@189",
  "params": {
    "value": 1
  }
}

Set Response

{
    "jsonrpc": "2.0",
    "id": 42,
    "result": "null"
}

Notifications

Notifications are autonomous events triggered by the internals of the implementation and broadcasted via JSON-RPC to all registered observers. Refer to [Thunder] for information on how to register for a notification.

The following events are provided by the IOConnector plugin:

IOConnector interface events:

Notification Description
activity Notifies about GPIO pin activity

activity notification

Notifies about GPIO pin activity.

Parameters

The id parameter shall be passed as index to the register call, i.e. register@<id>.

Notification Parameters

Name Type M/O Description
params object mandatory ...
params.value integer mandatory Value of the pin

Example

Registration

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "IOConnector.1.register@189",
  "params": {
    "event": "activity",
    "id": "myid"
  }
}

Notification

{
  "jsonrpc": "2.0",
  "method": "myid.activity@189",
  "params": {
    "value": 1
  }
}

The client ID parameter is passed within the notification designator, i.e. <client-id>.activity@<id>.