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justin
2024-01-25阅读836
EdgeX Foundry之Device Service SDK for Go应用

简介

DeviceService在Edgex Foundry中用于连接设备，他们直接与设备打交道，可以看作是设备的驱动吧。DeviceService作用的作用有：获取设备的状态；接收处理设备发过来的数据并发送到EdgeX；变更设备配置；设备发现。

DeviceService目前有两种语言的实现，分别为GoLang版本和C版本，其中主要还是使用GoLang版本的SDK。

环境

  • EdgeX Foundry 3.0

  • go1.20.4

  • 开发环境为GoLand 2023.2.2

应用步骤

1）新建一个go项目virtual-device-service-go

2）添加相关的edgexfoundry依赖

go get github.com/edgexfoundry/device-sdk-go/v3@v3.0.0
go get github.com/edgexfoundry/go-mod-core-contracts/v3@v3.0.0

3）创建对应的目录结构

下面会针对每一个文件做说明。

4）configuration.yaml

这个是Device Service的配置文件，内容如下：

Writable:
  LogLevel: INFO
  Reading:
    ReadingUnits: true
  InsecureSecrets:
    DB:
     SecretName: "redisdb"
     SecretData:
      username: ""
      password: ""

#配置客户端信息
Clients:
  core-metadata:
    UseMessageBus: false

#配置注册中心
Registry:
  Host: "edgex-core-consul"
  Port: 8500
  Type: "consul"

#配置当前服务的相关信息
Service:
  Host: "192.168.245.1"
  Port: 59911 # Device service are assigned the 599xx range
  HealthCheckInterval: "10s"
  RequestTimeout: "5s"
  StartupMsg: "virtual device service started"

#配置edgexfoundry的消息总线，默认是redis
MessageBus:
  Protocol: "redis"
  Host: "edgex-redis"
  Port: 6379
  Type: "redis"
  AuthMode: "none"
  SecretName: "redisdb"
  BaseTopicPrefix: "edgex"
  Optional:
    ClientId: "virtual-device-service-client"
    Retained: "false"
    AutoReconnect: "true"

#配置设备
Device:
  DataTransform: true
  AsyncBufferSize: 1
  MaxCmdOps: 128
  MaxCmdResultLen: 256
  EnableAsyncReadings: true
  ProfilesDir: "./res/profiles"
  DevicesDir: "./res/devices"
  Discovery:
    Enabled: false

具体的配置项内容可以参考官网：

https://docs.edgexfoundry.org/3.0/microservices/configuration/CommonConfiguration/

https://docs.edgexfoundry.org/3.0/microservices/device/Ch-DeviceServices/

5）profiles.yml

这个文件类似于设备的物模型配置。

apiVersion: "v3"
name: "virtualDemoProfile"
manufacturer: ""
model: "Virtual-Device-Profile"
labels:
  - "virtual-device-profile"
description: "虚拟模型定义"

deviceResources:
  - name: "Pressure"
    isHidden: true
    description: "压力"
    properties:
      valueType: "Uint32"
      readWrite: "R"
  - name: "FlowVolume"
    isHidden: true
    description: "流量"
    properties:
      valueType: "Uint32"
      readWrite: "R"
  - name: "Speed"
    isHidden: false
    description: "速度"
    properties:
      valueType: "Uint32"
      readWrite: "R"
  - name: "FrameRate"
    isHidden: false
    description: "帧频"
    properties:
      valueType: "Uint32"
      readWrite: "RW"
deviceCommands:
  - name: "ReadResult"
    readWrite: "R"
    isHidden: false
    resourceOperations:
      - { deviceResource: "Pressure" }
      - { deviceResource: "FlowVolume" }

这里我配置了四个属性：Pressure、FlowVolume、Speed、FrameRate，一个设备命令：ReadResult。需要重点说明的是，其中的配置项name很重要，这个就是profiles的唯一标识。

具体的配置项含义可参考官网：

https://docs.edgexfoundry.org/3.0/microservices/device/profile/Ch-DeviceProfileRef/

6）devices.yml

这是文件是配置设备信息的，在服务启动时，会从这个文件中加载对应的设备并注册到edgexfoundry中。

deviceList:
  - name: Virtual-Device-001
    profileName: virtualDemoProfile
    description: "虚拟设备"
    protocols:
      other:
        Address: 192.168.10.130
        Port: 3000
    autoEvents:
      - interval: 5s
        onChange: false
        sourceName: ReadResult
      - interval: 6s
        onChange: false
        sourceName: Speed

这里我定义了一个虚拟设备，并配置了自动上报的属性。其中的profileName关联的是这个设备对应的设备元信息是哪个，值就是在profiles.yml文件中配置的name。这里面的name就是设备的唯一标识。protocols是用来配置设备的协议，其实就是配置其连接信息。autoEvents配置设备需要定时上报的属性有哪些。

7）driver.go

这是文件可以说是核心实现，它是一个驱动文件，关于设备的所有控制都是通过这个文件中代码实现，下面我们看看这个文件中的具体实现：

package driver

import (
	"errors"
	"fmt"
	"github.com/edgexfoundry/device-sdk-go/v3/pkg/interfaces"
	sdkModels "github.com/edgexfoundry/device-sdk-go/v3/pkg/models"
	"github.com/edgexfoundry/go-mod-core-contracts/v3/clients/logger"
	"github.com/edgexfoundry/go-mod-core-contracts/v3/common"
	"github.com/edgexfoundry/go-mod-core-contracts/v3/models"
	"math/rand"
	"strconv"
	"sync"
)

type Driver struct {
	sdk    interfaces.DeviceServiceSDK
	logger logger.LoggingClient
}

var once sync.Once
var driver *Driver

func NewDriver() interfaces.ProtocolDriver {
	once.Do(func() {
		driver = new(Driver)
	})
	return driver
}

func (d *Driver) Initialize(sdk interfaces.DeviceServiceSDK) error {
	d.sdk = sdk
	d.logger = sdk.LoggingClient()
	return nil
}

func (d *Driver) HandleReadCommands(deviceName string, protocols map[string]models.ProtocolProperties, reqs []sdkModels.CommandRequest) ([]*sdkModels.CommandValue, error) {
	res := make([]*sdkModels.CommandValue, 0)
	for _, req := range reqs {
		var cv *sdkModels.CommandValue
		switch req.DeviceResourceName {
		case "Pressure":
			cv, _ = sdkModels.NewCommandValue(req.DeviceResourceName, common.ValueTypeUint32, rand.Uint32())
		case "FlowVolume":
			cv, _ = sdkModels.NewCommandValue(req.DeviceResourceName, common.ValueTypeUint32, rand.Uint32())
		case "Speed":
			cv, _ = sdkModels.NewCommandValue(req.DeviceResourceName, common.ValueTypeUint32, rand.Uint32())
		case "FrameRate":
			cv, _ = sdkModels.NewCommandValue(req.DeviceResourceName, common.ValueTypeUint32, rand.Uint32())
		}

		res = append(res, cv)
	}

	return res, nil
}

func (d *Driver) HandleWriteCommands(deviceName string, protocols map[string]models.ProtocolProperties, reqs []sdkModels.CommandRequest, params []*sdkModels.CommandValue) error {
	for i, r := range reqs {
		switch r.DeviceResourceName {
		case "FrameRate":
			d.logger.Infof("HandleWriteCommands: deviceName: %v, resource: %v, parameters: %v, attributes: %v",
				deviceName, reqs[i].DeviceResourceName, params[i], reqs[i].Attributes)
		}
	}
	return nil
}

func (d *Driver) Stop(force bool) error {
	if d.logger != nil {
		d.logger.Debugf("Driver.Stop called: force=%v", force)
	}
	return nil
}

func (d *Driver) Start() error {
	d.logger.Infof("Driver Start")
	return nil
}

func (d *Driver) AddDevice(deviceName string, protocols map[string]models.ProtocolProperties, adminState models.AdminState) error {
	d.logger.Infof("a new Device is added: %s", deviceName)
	return nil
}

func (d *Driver) UpdateDevice(deviceName string, protocols map[string]models.ProtocolProperties, adminState models.AdminState) error {
	d.logger.Infof("Device %s is updated", deviceName)
	return nil
}

func (d *Driver) RemoveDevice(deviceName string, protocols map[string]models.ProtocolProperties) error {
	d.logger.Infof("Device %s is removed", deviceName)
	return nil
}

func (d *Driver) Discover() error {
	d.logger.Infof("Device Discover")
	return nil
}

func (d *Driver) ValidateDevice(device models.Device) error {
	protocol, ok := device.Protocols["other"]
	if !ok {
		return errors.New("missing 'other' protocols")
	}

	addr, ok := protocol["Address"]
	if !ok {
		return errors.New("missing 'Address' information")
	} else if addr == "" {
		return errors.New("address must not empty")
	}

	port, ok := protocol["Port"]
	if !ok {
		return errors.New("missing 'Port' information")
	} else {
		portString := fmt.Sprintf("%v", port)
		_, err := strconv.ParseUint(portString, 10, 64)
		if err != nil {
			return errors.New("port must be a number")
		}
	}

	return nil
}

这是创建了一个结构体Driver，然后实现了驱动接口interfaces.ProtocolDriver，后面我会再说一下这个驱动接口中的各个方法是什么作用。

8）main.go

启动入口

package main

import (
	"github.com/edgexfoundry/device-sdk-go/v3"
	"github.com/edgexfoundry/device-sdk-go/v3/pkg/startup"
	"os"
	"virtual-device-service-go/driver"
)

const (
	serviceName string = "virtual-device-service"
)

func main() {
	//测试环境先禁用安全策略，生产环境中切不可如此使用
	os.Setenv("EDGEX_SECURITY_SECRET_STORE", "false")
	//这个是设置是否需要注册到注册中心的，也可以通过命令行指定
	os.Setenv("EDGEX_USE_REGISTRY", "true")

	deviceDriver := driver.NewDriver()
	startup.Bootstrap(serviceName, device.Version, deviceDriver)
}

9）执行

# 首先重构一下包依赖
go mod tidy

然后执行启动main.go，就可以在edgexfoundry的控制台看到对应注册的设备服务、设备、设备元数据以及上报的数据了。

 

 

 

下面是设备上报的数据格式

{
	"apiVersion": "v3",
	"id": "e7258b93-47b2-466a-ba47-c8eeffddb143",
	"deviceName": "Virtual-Device-001",
	"profileName": "virtualDemoProfile",
	"sourceName": "ReadResult",
	"origin": 1706149800827017200,
	"readings": [{
		"id": "7e8fa74a-4a59-4245-ac9f-0d896bc49698",
		"origin": 1706149800827017200,
		"deviceName": "Virtual-Device-001",
		"resourceName": "Pressure",
		"profileName": "virtualDemoProfile",
		"valueType": "Uint32",
		"value": "1906611700"
	}, {
		"id": "ce137306-9580-4aab-ba64-be1aeb8ad162",
		"origin": 1706149800827017200,
		"deviceName": "Virtual-Device-001",
		"resourceName": "FlowVolume",
		"profileName": "virtualDemoProfile",
		"valueType": "Uint32",
		"value": "4280818086"
	}]
}

到此，一个设备驱动也算是开发完成了。

补充说明

下面我来具体说一下驱动接口interfaces.ProtocolDriver中各个方法的作用，先看一下源码。

// -*- Mode: Go; indent-tabs-mode: t -*-
//
// Copyright (C) 2018 Canonical Ltd
// Copyright (C) 2018-2023 IOTech Ltd
//
// SPDX-License-Identifier: Apache-2.0

// Package interfaces defines interfaces and structs used to build an EdgeX Foundry Device
// Service.  The interfaces provide an abstraction layer for the device
// or protocol specific logic of a Device Service, and the structs represents request
// and response data format used by the protocol driver.
package interfaces

import (
	"github.com/edgexfoundry/go-mod-core-contracts/v3/models"

	sdkModels "github.com/edgexfoundry/device-sdk-go/v3/pkg/models"
)

// ProtocolDriver is a low-level device-specific interface used by
// other components of an EdgeX Device Service to interact with
// a specific class of devices.
type ProtocolDriver interface {
	// Initialize performs protocol-specific initialization for the device service.
	// The given *AsyncValues channel can be used to push asynchronous events and
	// readings to Core Data. The given []DiscoveredDevice channel is used to send
	// discovered devices that will be filtered and added to Core Metadata asynchronously.
	Initialize(sdk DeviceServiceSDK) error

	// HandleReadCommands passes a slice of CommandRequest struct each representing
	// a ResourceOperation for a specific device resource.
	HandleReadCommands(deviceName string, protocols map[string]models.ProtocolProperties, reqs []sdkModels.CommandRequest) ([]*sdkModels.CommandValue, error)

	// HandleWriteCommands passes a slice of CommandRequest struct each representing
	// a ResourceOperation for a specific device resource.
	// Since the commands are actuation commands, params provide parameters for the individual
	// command.
	HandleWriteCommands(deviceName string, protocols map[string]models.ProtocolProperties, reqs []sdkModels.CommandRequest, params []*sdkModels.CommandValue) error

	// Stop instructs the protocol-specific DS code to shutdown gracefully, or
	// if the force parameter is 'true', immediately. The driver is responsible
	// for closing any in-use channels, including the channel used to send async
	// readings (if supported).
	Stop(force bool) error

	// Start runs Device Service startup tasks after the SDK has been completely initialized.
	// This allows Device Service to safely use DeviceServiceSDK interface features in this function call.
	Start() error

	// AddDevice is a callback function that is invoked
	// when a new Device associated with this Device Service is added
	AddDevice(deviceName string, protocols map[string]models.ProtocolProperties, adminState models.AdminState) error

	// UpdateDevice is a callback function that is invoked
	// when a Device associated with this Device Service is updated
	UpdateDevice(deviceName string, protocols map[string]models.ProtocolProperties, adminState models.AdminState) error

	// RemoveDevice is a callback function that is invoked
	// when a Device associated with this Device Service is removed
	RemoveDevice(deviceName string, protocols map[string]models.ProtocolProperties) error

	// Discover triggers protocol specific device discovery, asynchronously
	// writes the results to the channel which is passed to the implementation
	// via ProtocolDriver.Initialize(). The results may be added to the device service
	// based on a set of acceptance criteria (i.e. Provision Watchers).
	Discover() error

	// ValidateDevice triggers device's protocol properties validation, returns error
	// if validation failed and the incoming device will not be added into EdgeX.
	ValidateDevice(device models.Device) error
}

  • Initialize：就是驱动文件的初始化，在服务启动中会被调用

  • HandleReadCommands：读取设备属性值的方法

  • HandleWriteCommands：执行上层下发的设备指令

  • Stop：服务停止时会调用，用于停止连接各个设备

  • Start：在服务启动完成之后会调用，用于启动驱动程序

  • AddDevice：在有设备被添加进来的时候调用

  • UpdateDevice：设备发生变更的时候调用

  • RemoveDevice：删除设备的时候调用

  • Discover：是一个设备自动发现的方法定义

  • ValidateDevice：验证设备是否可连接的方法

针对以上的方法，我们只需要实现对应的逻辑就行了，这些方法会在相对应的逻辑中被edgexfoundry直接调用。

golang
edgexfoundry
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justin
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