I. Project Overview
1.1 Introduction
The Internet of Things (IoT) is an important component of the next generation of information technology. As the name suggests, the IoT is an "internet connecting things." The IoT is defined as a network that connects any object to the internet through information sensing devices such as RFID, infrared sensors, GPS, and laser scanners, according to agreed-upon protocols, enabling information exchange and communication, thereby achieving intelligent identification, location, tracking, monitoring, and management of objects.
1.2 Project Background/Motivation for Topic Selection
The Internet of Things (IoT) technology has rapidly developed as a product of the third information revolution, and its influence can be seen in various fields, from industrial sites to home life. First, the core and foundation of the IoT remains the internet; it is an extension and expansion of the internet. Second, its user end extends to any object-to-object communication for information exchange. Based on this, we designed related works.
II. Requirements Analysis
2.1 Functional Requirements
The intelligent sensor node in this design performs the following tasks:
1. It has multiple sensor input interfaces (such as those for detecting ambient temperature, humidity, and light intensity);
2. Simultaneously acquire signals from multiple sensors;
3. The node has a network interface, allowing remote login via a webpage to observe the node;
4. It allows for the setting of node parameters, such as sensor calibration, scaling transformation, and switching of redundant sensors;
5. It can realize certain control functions, and the output signals are voltage, current and PWM, which control the corresponding actuators to complete closed-loop control, and the PID control parameters can be selected.
2.2 Performance Requirements
1. Design of sensor interface circuit;
2. Computer network technology, TCP/IP protocol analysis, and implementation of embedded web servers;
3. Sensor calibration, scaling transformation, and redundancy backup technology;
4. Output interfaces for control signals such as voltage, current, and PWM;
5. Implementation methods and algorithms for closed-loop control systems;
6. Implementation of digital PID algorithm and parameter tuning, etc.
III. Scheme Design
3.1 System Function Implementation Principle
1. It has multiple sensor input interfaces (such as those for detecting ambient temperature, humidity, and light intensity);
2. Simultaneously acquire signals from multiple sensors;
3. The node has a network interface, allowing remote login via a webpage to observe the node;
4. It allows for the setting of node parameters, such as sensor calibration, scaling transformation, and switching of redundant sensors;
5. It can realize certain control functions, and the output signals are voltage, current and PWM, which control the corresponding actuators to complete closed-loop control, and the PID control parameters can be selected.
3.2 Hardware Platform Selection and Resource Configuration
The evaluation kit and development system EVK1100 based on the AVR32 AT32UC3A microcontroller controller were selected.
1. Use some of the onboard sensors for testing;
2. Connect to the Ethernet network using the onboard Ethernet port;
3. SPI expansion SD card interface to expand large-capacity memory for storing historical data;
4. Usage of other hardware resources:
A. USART serves as a debugging aid and another means of setting or displaying parameters.
B. Processor's PWM signal output method
C. The processor's internal AD converter serves as the analog signal input channel.
D. The processor's internal counter serves as the input channel for external frequency signals.
E. The processor's internal timer acts as a task switching allocator.
F. Processor internal or external EEPROM storage settings and network address information.
3.3 System Software Architecture
1. Modular programming;
2. The main program polls tasks in the system based on timer time slices (no OS);
3. Ethernet communication module, porting uIP network protocol package;
4. Sensor parameter setting and information acquisition module (containing multiple sub-modules);
5. Control parameter setting and control output module (containing multiple sub-modules);
6. Serial communication module;
7. SD card read/write module;
8. Keyboard and display module;
9. Basic Information Parameter Setting Module
3.4 System Software Flow
Note: Some tasks may be unnecessary at a certain state; polling will skip these tasks.
3.4 Expected System Results
The hardware and software for implementing this project can be accessed via a network from a local or remote computer. It allows setting sensor input-output relationships (scaling transformation formulas), displaying normal physical quantities of the sensors on a webpage, such as current temperature, humidity, and light intensity, and showing historical curves of these parameters. It can also acquire and save historical data via the network. Furthermore, it enables the designed project to perform certain control functions, such as temperature and water level control without human intervention. Control parameters are designed via a webpage, and the system has a simple human-computer interaction interface.
