3.1.3 Smart Wireless Thermostat on PIC32CZ CA90 Curiosity Ultra Development Board

Description

This wireless thermostat application uses Bluetooth Low Energy 5.2 and Wi-Fi technology to collect real-time temperature data from two BLE sensor nodes. It allows users to easily set and control the temperature, creating a pleasant environment by adjusting the heating or cooling system to their desired level through an intuitive BLE central node acting as a wireless thermostat that connects to the end nodes over BLE and acts as the temperature control panel. The collected temperature is streamed through the Wi-Fi Gateway node to the AWS IoT cloud for monitoring. This solution includes four projects to demonstrate a Wireless Thermostat.

• Wireless Thermostat Central Control Panel - (PIC32CZ_CA90 Central BLE Node Application):

  This project employs the RNBD451 BLE module to create multi-link BLE connections with two peripheral nodes. Once connected, the central node functions as a GATT client, periodically requesting real-time temperature data from the peripheral GATT servers(peripherals) and displaying it on a 4.3-inch maXTouch® graphics display. Users can set and send temperature threshold limits to the BLE peripheral nodes using the GUI. In addition, the central application transmits the gathered temperature data to the WFI32 IoT gateway through UART for real-time monitoring on the AWS cloud.

• Wireless Thermostat Peripheral BLE Sensor Node 1 - (PIC32CM_LS60 BLE Peripheral Node):

  This application operates as a GATT server using the RNBD451 BLE module. It periodically collects temperature data from the IO/1 Xplained Pro board and updates the temperature characteristic value whenever the temperature changes. The node waits for the connection request from the central node. Once connected, it sends temperature data in response to read requests from the GATT client(central node) and can receive and implement threshold limit values from the central node. An onboard LED turns on whenever the temperature exceeds the designated limit.

• Wireless Thermostat Peripheral BLE Sensor Node 2 - (WBZ451 BLE Peripheral Node):

  This application uses ADC to read the analog output from the onboard MCP9700A temperature sensor. Once connected to central node over BLE, it periodically sends the temperature characteristic value to the central node upon request. It can receive and set threshold limit values from the central node, with an onboard LED illuminating when the temperature surpasses the defined cutoff.

• Wireless Thermostat Gateway - (WFI32 IoT Wi-Fi-Gateway):

  This application acts as bridge between the central node and the AWS cloud. It periodically receives the BLE end nodes temperature data from the central over UART and publishes the same over MQTT to the AWS IoT cloud for constant monitoring.

Modules/Technology Used

Hardware Used

Software/Tools Used

The projects have been verified to work with the following versions of software tools:

• For Central PIC32CZ_CA90 GATT Client, refer to the Project Manifest
• For peripheral PIC32CM_LS60 GATT Server, refer to the Secure Project Manifest and Non-Secure Project Manifest
• For peripheral WBZ451 GATT Server, refer to the Project Manifest
• For Wi-Fi Gateway PIC32MZ_W1, refer to the Project Manifest
• MPLAB® X IDE v6.20
• MPLAB® XC32 C/C++ Compiler v4.45
• Any Serial Terminal application, such as Tera Term terminal
• Python v3.5 or higher

Due to Microchip regularly updates tools, occasionally issue(s) could be discovered while using the newer versions of the tools. If the project does not seem to work and version incompatibility is suspected. It is recommended to double-check and use the same versions that the project was tested with. To download original version of MPLAB Harmony v3 packages, refer to the document How to Use the MPLAB Harmony v3 Project Manifest Feature (DS90003305).

Hardware Setup

• Connect the WFI32 IoT development board to the host PC as a USB device through a Type-A male to Micro-B USB cable connected to PKOB4 Micro-B USB (Debug USB) (J200)

  

Prerequisites

• The WFI32E01PC module on the WFI32 IoT development board has an in-built Trust and Go (TNG) device. It is essential to upload the device certificate of the TNG device to the AWS IoT cloud for authenticated client TLS connection with the cloud platform.
• Follow the procedure mentioned in Generate Device Certificate for extracting the certificate from the device.
• Upon generation, the device certificate should be uploaded to the cloud. Refer to the Uploading Device Certificate to AWS IoT Cloud Service section for more details about the procedure.
• The configuration.h file of wfi32_iot.X project should be modified for connecting successfully to the AWS cloud.
  • Ensure that the WIFI SSID and WIFI Password is modified in the file by changing the SYS_WIFI_STA_SSID and SYS_WIFI_STA_PWD macros with the Wi-Fi credentials.
  • Ensure that the aws endpoint and aws thing name are properly set in the SYS_MQTT_INDEX0_BROKER_NAME and SYS_MQTT_INDEX0_CLIENT_ID macros respectively. This depends on user-specific AWS account credentials. For more details, refer to the AWS Account Setup section.

Programming Methods

Method 1: Programming Prebuilt Hex File

• Open MPLAB X IDE
• Close all existing projects in IDE, if any project is opened
• Go to File>Import>Hex/ELF file
• In the Import Image File window,
  1. Create Prebuilt Project,
     • Click the Browse button to select the prebuilt hex file
     • Select Device as PIC32CZ8110CA90208
     • Ensure the proper tool is selected under Hardware Tool and click the Next button
  2. Select Project Name and Folder,
     • Select appropriate project name and folder and click the Finish button
• In MPLAB X IDE, click the Make and Program Device button to program the device
• Follow the steps in Running the Demo under PIC32CZ CA90 Central section below

Method 2: Programming/Debugging the Application Project

Running the Demo

PIC32CZCA90 BLE Central Node

• Power up the board. Ensure the 4.3" WQVGA maXTouch Display Module is connected to the 565 LCD Adapter Graphics Card and press RESET button of the PIC32CZ CA90 Curiosity Ultra development board.

Screen 1: Home Screen

• The home screen of the demo gets displayed on the 4.3” WQVGA maXTouch Display Module.

  

• Ensure that the BLE peripheral nodes, NODE 1 and NODE 2, are programmed with the respective application projects and both the nodes are ready to connect to the central node.
  Note: Before proceeding to the next step, ensure the console messages shown on the peripheral Node 1 and Node 2 are as Node 1 Ready Status and Node 2 Ready Status.
• Press the START button on the home screen.

  

Screen 2: Multi-Connect Screen

• The central node starts to scan for the nearby BLE peripheral nodes. Scanning appears on the connect screen. Wait for a few seconds for the BLE scanning process to complete.
• Once the scanning completes, the central initiates connection with BLE Node 1.

  

• Upon successful connection with BLE node 1, a tick mark appears on the GUI as below and LED0 is turned on.

  

• Similarly , the central node initiates another connection to BLE node 2.
• Upon successfully connecting with the second node, a tick mark appears on the GUI, as below, and the next screen appears that shows Preparing appears.
• LED0 and LED1 are turned on with a successful multilink connection on the PIC32CZ CA90 Curiosity Ultra development board as below.

  

Screen 3: Multi Node Sensor Monitoring

• This screen gets updated with node 1 and node 2 temperature data fetched in periodic intervals from the BLE peripheral devices.

  

  Note: The corresponding temperature can be viewed on the Tera term console of nodes 1 and 2.
• Press Set Limit button to assign threshold limit for the nodes to cutoff the heating or cooling unit. Once Set Limit is pressed the next screen appears.
  Note: Wait for a couple of seconds if the next screen does not appear immediately.

Screen 4: Temperature Control

• Temperature limits can be set for each of the nodes using the ᴧ (Increment) and v (Decrement) buttons.

  

• To set threshold for node 1, adjust the temperature and press Enter.
• Similarly, to set threshold for node 2, adjust the temperature for node 2 and press Enter.
  Note: Take into account that the limits for each node should be set individually. The nodes do not get updated simultaneously. To set threshold for both the nodes, change the limit in one node, press enter and then do the same for the other node.
• Press Press to Go back to go to screen 3.

PIC32CM LS60 BLE Peripheral Node

• Power up the board
• Open the Terminal application (e.g., Tera term) on the computer
• Change the baud rate to 115200

  

• Press RESET button of the PIC32CM LS60 Curiosity Pro evaluation kit to run the application from the beginning
• The below console output will be displayed. The last message on Tera Term will be Connecting where the node waits for a BLE connection

  

• When the central node successfully connects (after pressing start on the central node GUI), the LED0 (Green LED) turns on indicating successful connection

  

• The measured temperature value prints on the console as below

  

• The BLE node receives the temperature threshold values set on the central node as below

  

• LED1 (Red LED) on PIC32CM LS60 Curiosity Pro evaluation kit turns on whenever the current temperature is greater than the set limit

  

WBZ451 BLE Peripheral Node

• Power up the board
• Open the Terminal application (e.g., Tera term) on the computer
• Change the baud rate to 115200
• Press RESET button to start over the application
• The device starts BLE advertisement and displays the current temperature in periodic intervals

  

• Once the connection with the central node is successful, it sends the current temperature value to the central node

  

  

  

• The BLE node receives the temperature threshold values set on the central node
• The RGB LED (D6) of the WBZ451 Curiosity development board glows in Red when the current temperature exceeds the threshold set. In the above image the current temperature (31°C) is greater than the received threshold (22°C). The LED turns on in this scenario.

  

WFI32 IoT Wi-Fi Gateway Node

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