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Micriµm YWireless-RX65N Smart Home Gateway - Getting Started Guide

Micriµm YWireless-RX65N Smart Home Gateway

Getting Started Guide Introduction

There are countless resources to build an IoT system with. Embedded engineers are faced with a large variety of protocols, cloud services, platforms, techniques and solutions to choose from. Because most of these resources seem disjointed, we put together a complete set of resources required to develop an IoT device and integrated in a larger system.

In order to help you compliment the knowledge you are getting in this guide, we believe that some hands-on experience will help understanding the concepts at play.

The purpose of this getting started guide is to introduce embedded engineers to the Renesas YWireless-RX65N Smart Home Gateway application. This application will use the following resources:

§ The Renesas YWireless-RX65N platform. § The IAR Systems Embedded Workbench for RX. § The Micriµm µC/Probe run-time graphical live watch tool. § TheAmazonWebServicesIoTplatform. § Micriµm embedded software.

Objectives

After completing this hands-on session, you will be able to:

§ Build an IAR project for the YWireless-RX65N and program the board. § Use Micrium’s uC/Probe to interact with the YWireless-RX65N. § See your YWireless-RX65N based IoT device send data to and receive data from the

AWS IoT platform. § Understand what the AWS IoT platform is and how it’s used.


Setup

The setup for this guide requires the following elements:

§ A laptop/desktop with internet connectivity. § A Renesas YWireless-RX65N board. § A Renesas E1 programmer. § A WiFi router with access to the Internet

o The router can be secured with an SSID and a password but could not contain other authentication like an additional web authentication as often found in hotels or public places.

Laptop/desktop prerequisite

Software tools required on the computer:

§ IAR Embedded Workbench for RX (EWRX) compiler and debugger. § Micriµm µC/Probe, a data visualization tool for embedded target variables. § Google Chrome for access to the webpages displaying the data generated and required

by the embedded target.


1. AWS Overview

1-1. Introduction Amazon Web Services (AWS) is a secure cloud services platform, offering computing power, database storage, content delivery and other functionality for developers in an on-demand cloud. It originally launched in 2006 to provide a cloud for web sites and client side applications. Since then it has grown to over 50 different services and an estimated third of the Internet is hosted on, or interacts with, AWS in some fashion. The main focus of this guide is AWS IoT, the IoT platform launched in October 2015. More details on AWS IoT are provided in the next section.

1-2. AWS IoT

This graphic shows the architecture of AWS IoT and how data flows through it. To fully understand how messages are passed into AWS IoT, we need to break it into two parts: security and protocol. Beyond how messages are passed into AWS IoT will be covered in later sections of this guide.


1-2-1. Security Before we can even begin to discuss the protocol and message type that is sent to AWS IoT, we first need to “get in the front door”. All connections to AWS IoT require a mutually authenticated TLS connection. This is different than a normal TLS/SSL connection you would have on a web page where you see an icon similar to this

A normal web page SSL connection is one-way where the server you’re connecting to presents you with a certificate that has been signed by a Certificate Authority. Your browser has a list of acceptable Certificate Authorities and checks the certificate presented by the server against this list. If it matches the browser decides this is a trustworthy connection and accepts the certificate. A mutually authenticated TLS connection takes the above a step further. In our connection with AWS IoT, we will be presented with a certificate from AWS so we can decide if we want to trust AWS similar to your browser received a certificate from a server. But our IoT device also has to present AWS IoT with a certificate so AWS IoT can decide if they want to trust this device. The certificate is also used as a sort of username/password for access control.

1-2-2. Protocol AWS IoT messages are sent primarily via the message protocol Message Queue Telemetry Transport (MQTT). This guide will not get into the details on the MQTT protocol, but more information on the protocol can be found at http://www.mqtt.org.

The MQTT protocol sits right above TCP, is extremely lightweight and is ideal for small embedded devices. While it will not be covered in this guide, data can also be sent to AWS IoT via Websockets and HTTP. Both of those protocols are much heavier than MQTT and not practical for an embedded device. At this point we have enough background information to get started.


2. IAR Configuration

2-1. Configuring the Smart Home Gateway application in IAR

Open the IAR Systems Embedded Workbench for RX (EWRX) by clicking the shortcut on the desktop or via searching in the Start Menu or Windows Explorer.

Once EWRX is running, click File → Open → Workspace… and browse to the workspace file OS3-TCPIP-WIFI.eww located at the following path:

└───Micrium └───Examples └───Renesas └───YWIRELESS-RX65N

└───OS3-TCPIP-WIFI └───IAR

The workspace will open in a window similar to the one shown in the image below:


First we need to configure the WiFi parameters. Open the file app_cfg.h found under the APP directory in IAR. Around line 132 you will find the WiFi configuration. Ensure the configuration is as follows:

APP_CFG_WIFI_NET_SSID: Your WiFi SSID APP_CFG_WIFI_NET_PSK: Your WiFi Password

2-2. Configuring IAR for E1 and uC/Probe In order to program and debug the YWireless-RX65N we need to configure it for the Renesas E1 programmer. Also, since we will be using uC/Probe at the same time as debugging we need to enable the uC/Probe plugin in IAR.

Right click on the project as shown above and select Options.


Click on the Debugger category as shown above and change the Driver to E1/E20. Also make sure the Run to: box is selected and set to run to main.


Next, remain in the Debugger category and click on the Plugins tab. Scroll to the bottom of the plugins and check the uC/Probe plugin as shown above.


2-3. Compiling the application in IAR

Right click on the project again and choose Rebuild All. This will clean the project and build everything from scratch.

After the build you should see Linking followed by Total number of errors: 0. If the total number of errors is not zero, scroll up in the build log to determine the error, fix the errors and attempt to build again.


2-4. Powering and connecting the YWireless-RX65N

At this point we are just about ready to program the YWireless-RX65N with our application. Before we can we must connect the power to the target and connect the E1 programmer.

The YWireless-RX65N is powered by the USB mini port as shown below. You can connect the USB cable to your computer or to any USB power source, the device will not enumerate. Next connect the E1 to the programming port as shown below.

USB Mini Port

E1 Connector


3. Flashing and running the Smart Home Gateway In IAR click the Download and Debug button on the toolbar or select Project → Download and Debug to flash the application to the YWireless-RX65N. This will cause a window to pop up with the following:

While launching the debug session, the debugger will flash the board, verify the programming, load the debug file and verify it. It may take up to a minute. Once IAR finishes flashing and verifying the code will run until it hits main() and then break. At this point you can hit the Go button to start the application.

The application will start µC/OS-III and µC/TCP-IP. The µC/DHCPc (DHCP Client) will negotiate an IP Address assuming that your network has a DHCP server available. Once an address is pulled the AWS IoT module will establish a connection with the AWS IoT broker and then signal to the Smart Home Gateway application that it can begin to pass messages to AWS IoT.

Since there is no graphical display on this board we will use uC/Probe to interact with the target as shown in the next section. There are however LEDs that give the status of the boards WiFi connection.

Go


There are three LEDs used on the YWireless-RX65N to indicate the status of the board:

Heartbeat LED – This is controlled in its own task. If its not blinking either the debugger has hit a breakpoint or the OS has crashed.

Yellow LED – The YWireless-RX65N is still trying to establish a connection with the network.

Green LED – The YWireless-RX65N has established a network connection and is online.

Heartbeat LED

Yellow LED

Red LED


4. Using the Smart Home Gateway with µC/Probe µC/Probe is a graphical live watch tool that allows for run-time data visualization. µC/Probe takes advantage of the newer processor architectures allowing for reading/writing memory locations while the processor is running. µC/Probe can access the embedded target via various communication channels:

• J-Link JTAG probe • CMSIS DAP • IAR C-Spy (interfacing with other JTAG probes) • TCP/IP (Ethernet or WiFi) • RS-232 • USB

The IoT example featured in this getting started guide runs a simulator to create data for a Smart Home Gateway. The Smart Home Gateway (SHG) is a demonstration of a consumer-oriented use case for the IoT. The use case is that of a household with smart appliances communicating over a personal area network. In this example the home is equipped with three appliances and three temperature sensors. Each device publishes its data about it’s state on a set interval, but if any changes are made to the state of an appliance or temperature value the data is published immediately. The gateway publishes this data using the MQTT protocol to AWS IoT. This allows us to use this data in AWS in any way we desire. Similarly, data is published from AWS IoT down to the Smart Home Gateway in the form of commands which allows us to remotely control the Smart Home Gateway.

The SHG demo fulfills two roles: it simulates the devices and it acts as the gateway between the simulated environment and the MQTT broker. The simulated devices and their related MQTT topics are described in greater detail below.

Resources Appliances Temperature Sensors Dishwasher Kitchen Dryer Family Room Lamp Garage

In this guide you will use µC/Probe to control and monitor the simulation through a dashboard that contains controls to modify the appliance state and temperature value. At the same time, the dashboard will display the appliance state and current temperature values.


4-1. Configuring uC/Probe

TodownloadafreetrialofuC/Probeusethislink:https://www.micrium.com/ucprobe/trial/

Look for the µC/Probe icon on the desktop or in the start-up menu.

Click File → Open to open the dashboard example file SmartHomeGateway.wspx located at the following path:

└───Micrium └───Examples └───Renesas └───YWIRELESS-RX65N

└───OS3-TCPIP-WIFI

Click the Settings button located in the top toolbar of µC/Probe and configure the Communication Settings to TCP/IP. In the Settings box the Remote Host and Remote Port will be set to IAR. Ensure the remote host and port are set to:

Remote Host: localhost Remote Port: 9930

.

Click OK then click the Run button located in the top toolbar of µC/Probe.


4-2. Using the Smart Home Gateway dashboard

Once you hit the run button, Probe will load the Smart Home Gateway dashboard as shown above. The left hand side of the dashboard allows you to control the appliance state and the temperature value. These values are then represented on the right hand side of the dashboard. Any changes made to the variable states will immediately be pushed to AWS IoT and any changes made remotely will be reflected here as soon as the message is received.


5. Monitoring and controlling the YWireless-RX65N from the Web

AWS IoT is the platform where all the data generated by the embedded target is published. The IoT device connects to this platform using MQTT; a simple publish/subscribe protocol. For more information about MQTT please visit http://mqtt.org

Your IoT device is periodically publishing the latest embedded target simulation data values to the MQTT broker at Amazon. At the same time, the IoT device subscribes to a topic to receive any requests from a remote MQTT client to control the Smart Home Gateway.

In this exercise you will use your internet browser to control and monitor the appliance state as well as monitor the room temperatures as you modify them in Probe.

5-1. Viewing the MQTT data on the web

Open an internet browser such as Google Chrome and go to the following address: https://mqtt.micrium.com/

Ensure the Training/Non-Micrium Account box is not checked.

Enter your YWireless-RX65N’s MAC address for the Thing ID field. You can find the Thing ID on the Probe Workspace as shown below. Do not put colons or dashes between the octets.


Once the Thing ID field has been filled out click on the Create Client button.

If your screen stays like the above picture (orange boxes, 0 appliances and 0 sensors) for longer than three minutes, check that your YWireless-RX65N heartbeat LED is blinking and the green LED is lit. If the heartbeat is not blinking ensure you have IAR debugging and its not at a breakpoint. If the heartbeat is blinking but the yellow LED remains lit, check your WiFi settings.

Once the web page receives data from the YWireless-RX65N it will populate the screen with the appliances and temperature sensors as shown in the pictures below.

Thing ID


Any local action done using µC/Probe will be reflected remotely on the webpage and any remote action done on the webpage will be reflected locally and displayed using µC/Probe. At this stage, we see that the communications between the IoT device, AWS IoT and the webpage are bidirectional. From this point, what a system based on this architecture can do is only limited by your creativity.


6. MQTT in the Smart Home Gateway

6-1. MQTT Topics and Messages

The MQTT protocol is based on the principle of publishing messages and subscribing to topics. A device publishes its data as a message with an associated topic. Subscribing applications need to know which device originally published each received message.

MQTT supports a hierarchical topic namespace. This allows application designers to organize topics to simplify their management. Levels in the hierarchy are delimited by the '/' character, such as:

com.ucos/appliance/001122334455

Two wildcard characters are supported to ease subscriptions to multiple messages:

• A '#' character represents a complete sub-tree of the hierarchy and thus must be the last character in a subscription topic string, such as com.ucos/#. This will match any topic starting with com.ucos/, such as com.ucos/appliance/001122334455 and com.ucos/temperature/012345012345.

• A '+' character represents a single level of the hierarchy and is used between delimiters. For example, com.ucos/+/001122334455 will match com.ucos/temperature/001122334455 and com.ucos/appliance/001122334455 but not com.ucos/appliance/012345012345.

Deciding on your topic hierarchy is an important step in your system design.

An MQTT message is what gets passed through the MQTT topics. The type of data sent as the message payload is only limited by your use of it. Some common formats are JSON, null terminated strings and binary data. The type of payload you send is usually application dependent. For example, if you are transmitting data over a cellular network where you are charged for every MB you send, it probably does not make sense to send data in a complex JSON payload. Whereas if you are connected over a WiFi network it may be completely reasonable to send a JSON payload to simplify storing data in a database or displaying the data on a web page.


6-2. Smart Home Gateway Topics and Messages

In the Smart Home Gateway application we utilize two main topics: appliance and temperature. Each topic has messages for each item in their topic category.

All messages passed back and forth are formatted in JSON. If you are not familiar with JSON you can read about the format here: https://en.wikipedia.org/wiki/JSON

6-2-1. Appliance Messages

The Smart Home Gateway simulates three appliances: Dishwasher, Dryer, and a Lamp.

All of the appliances pass data in the same JSON format on the topic com.ucos/appliance/thingid:

{“appliance” : {“state” : “0/1”, “milliamps” : “current_consumed”}}

Each appliance passes it’s state as a 0 for off and 1 for on. It also passes a field millamps used to keep track of how much energy each appliance uses. In this example we will not use the milliamps field.

To control an appliances state, the YWireless-RX65N subscribes to the topic com.ucos/appliance/cmd/thingid. The message format for controlling an appliance remotely is:

{“appliance” : {“state” : “0/1”}}

When the YWireless-RX65N receives a message on the command topic, it will change the appliance’s state which then forces the YWireless-RX65N to immediately publish that appliance’s new state.

6-2-2. Temperature Messages

The Smart Home Gateway simulates monitoring the temperature of three rooms in a house: Family Room, Kitchen and Garage.

{“room” : {“F” : “temperature_val”, “humidity” : “humidity_val”}}

Each temperature sensor passes the temperature in Fahrenheit and the humidity percentage (0 – 100). In this example we will not use the humidity value.

There is no command channel for the temperature sensors as the sensors we are simulating are not configurable.


7. Conclusion We hope you found this getting started guide useful. You can find additional information on AWS IoT at:

https://aws.amazon.com/documentation/iot/ For more information on the Micrium software used or how to use this software with your own AWS account, contact Micrium using the form found here:

https://www.micrium.com/spectrum/

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