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How is the crystal oscillator laid out on the PCB?
How is the crystal oscillator laid out on the PCB?
Crystal oscillators generally refer to two types of quartz crystal oscillators and quartz crystal resonators, and can also be directly called crystal oscillators. They are all made using the piezoelectric effect of quartz crystals.
Its working principle is as follows: when an electric field is applied to the two electrodes of the crystal, the crystal will undergo mechanical deformation. Conversely, if mechanical pressure is applied to both ends of the crystal, the crystal will generate an electric field again. This phenomenon is reversible, so using this property of the crystal, applying an alternating voltage across the crystal will cause the wafer to vibrate mechanically and at the same time generate an alternating electric field. However, the vibration and electric field generated by the crystal are generally very small, but as long as it is at a certain frequency, the amplitude will increase significantly, just like the LC circuit resonance that our circuit designers often see.
Single serial port server
WIFI serial server
Signal interface conversion
Ethernet
CAN module
Crystal oscillator classification:
① Passive crystal oscillator
The passive crystal oscillator is a crystal, generally a 2-pin non-polar device (some passive crystal oscillators have non-polar fixed pins).
Passive crystal oscillators generally require the help of a clock circuit formed by a load capacitor to generate an oscillating signal (sine wave signal).
②Active crystal oscillator
Active crystal oscillators are oscillators, usually 4 pins. The active crystal oscillator does not require the CPU's internal oscillator and generates a square wave signal. An active crystal oscillator power supply can generate a clock signal.
The signal of the active crystal oscillator is stable, the quality is better, and the connection method is relatively simple, The accuracy error is smaller than that of a passive crystal oscillator, and the price is more expensive than the passive crystal oscillator.
PR
Have you heard of "acid horn" in PCB design
To know what tamarind is, it is important to understand the PCB production process! Engineers who know something about the PCB production process know that before PCB production, the PCB diagram is drawn through circuit board design software, and then goes through the etching process of the PCB processing factory, and finally the designed PCB circuit is etched on the copper-clad board.
Single serial port server
WIFI serial server
Signal interface conversion By the way, a basic flow chart of PCB production process is attached Among the basic processes of PCB production process, the most important is the etching process. It uses chemical treatment to remove unnecessary copper from the copper-clad board through etching, and then leaves the required circuit diagram. To a certain extent, Acid Traps can be said to be left by etching. "side effects".
The chemicals used to etch circuits should be removed during the neutralization and water washing process, but in the acute angle area formed by the PCB connection, that is, the narrowest acute angle, it is easy to cause corrosive chemicals to remain, which is like a trap to surround and suppress the residual corrosive chemicals. substance.
By slowly and continuously corroding the copper in the acute-angle area, over time, the line resistance of the wiring will increase or a virtual connection state will occur, and short circuit faults will easily occur, making troubleshooting difficult. This is the headache of Acid Traps. "corner" phenomenon. PCB trace angle problem This involves a PCB trace angle issue.
Everyone has always emphasized: Don’t trace traces at right angles! So, here comes the question. If you are not allowed to go at a right angle, is it better to go at a 45° angle or an arc? Is 90° right-angle routing really okay? At first, I was obsessed with the corner angle of the wiring. I looked up the history of our predecessors. In the 1990s, Intel launched PCI bus technology. Since then, it has accelerated the development of "high-speed" systems. As for whether PCB traces can go at sharp angles, the conclusion is definitely not possible. From the perspective of PCB DFM, sharp angles in PCB traces should be avoided, and acid traps should be avoided as much as possible.
HTTP is essentially a TCP connection
HTTP is essentially a TCP connection, but the protocol stipulates the use of port 80 and the format for sending commands or data, while TCP itself has no encryption function. The fatal thing is that during the data transmission process of HTTP, the data is transmitted in clear text. Since the data is not encrypted, it is easy for unsafe behaviors such as data eavesdropping, tampering or identity forgery to occur.
Is there any way to optimize it?
Since it is not safe to use plain text for data transmission, we can try to encrypt the data. For example, the communicating parties can agree on an algorithm that first encrypts the data to be sent according to certain rules,GPRS DTU and then decrypts it according to the same rules after the other party receives the message. This is the embodiment of symmetric encryption.
The so-called symmetric encryption means that the original text and the ciphertext can be encrypted and decrypted using the same key, that is, the same key can be used to encrypt the original text to obtain the ciphertext or to decrypt the ciphertext to obtain the original text. The advantage is that the encryption and decryption efficiency is high.
But there is a key point in using symmetric encryption, that is, the symmetric key. How to determine it? In HTTP requests, encryption key negotiation is still a difficult problem.
How does HTTPS ensure data security?
Data is encrypted during HTTPS data transmission. HTTPS uses symmetric encryption and asymmetric encryption, signature algorithms (signature algorithms are not used for encryption) and certificate mechanisms to process messages to achieve a safe and effective transmission.
HTTPS is based on the upper layer of HTTP and adds a security layer called TLS. Operations such as data encryption are processed in this security layer, and the bottom layer is still the HTTP of the application. HTTPS communication first uses asymmetric encryption to negotiate keys and negotiates a symmetric encryption key. Subsequent communications use this symmetric key for symmetric encryption ciphertext transmission. Because the algorithm of asymmetric encryption is extremely complex, the decryption efficiency is low, while the efficiency of symmetric encryption is significantly higher than a hundred times.
As we mentioned above, using the same key to encrypt and decrypt plaintext is symmetric encryption. So what about asymmetric encryption?
asymmetric encryption
Asymmetric encryption, that is, the original text encryption and the ciphertext encryption use two different keys, one is called the public key and the other is called the private key. Content encrypted using the public Industrial Router/Gateway key can be decrypted through the private key. Likewise, content encrypted using the private key can be decrypted using the public key. Public keys and private keys are relative. Generally speaking, the ones that are kept by oneself and cannot be disclosed to the public are called private keys, and the ones that can be released to the public are called public keys.
Asymmetric encryption uses different keys to encrypt and decrypt plaintext. However, we mentioned above that when using encryption, the difficulty lies in the key agreement process. So, how does HTTPS handle this key agreement process.
Integrating BLE with Cloud Services: Building a Comprehensive IoT Solution
With the rapid development of the Internet of Things (IoT), integrating Bluetooth Low Energy (BLE) technology with cloud services has become an important part of realizing a comprehensive IoT solution. This article will take a deep dive into the integration of BLE with cloud services and how this integration enables smarter and more efficient IoT applications.
Integration advantages of BLE and cloud services
Data collection and storage: BLE sensors can collect environmental, health, safety, and other data, and send them to the cloud for storage and analysis. Cloud services provide large-capacity data storage, enabling users to access and analyze data anytime and anywhere.
Real-time monitoring: Combining BLE and cloud services, users can monitor sensor data in real-time. When data reaches a certain threshold, cloud services can send alerts to notify users, helping to take timely action.
Remote Control: BLE-connected devices can be remotely controlled through the cloud. Users can remotely control home appliances, Low-power wireless communication smart devices, etc. through cloud service applications.
Data analysis and insights: Cloud services provide powerful data analysis tools to help users extract valuable information from massive amounts of data and discover trends and patterns.
Flexibility: Cloud services make device deployment and management more flexible. Devices can be added, removed or updated at any time, while services in the cloud do not require large-scale physical deployment.
BLE Network Topology and Connectivity: Exploring Wireless Connectivity Architectures in IoT
In the rise of the Internet of Things (IoT), Bluetooth Low Energy (BLE) technology plays a key role in connecting IoT devices. BLE not only provides a low-power solution for communication between devices, but also has a variety of network topologies and connectivity options. This article will provide an in-depth look at the different types of BLE network topologies, and their applications and benefits in IoT.
Peer-to-peer (P2P) topology: This is the simplest BLE network topology, suitable for direct communication between two devices. Point-to-point connections are generally stable and suitable for one-to-one data transfers, such as sensor data uploads or remote control operations.
Star topology: In a star topology, one central device (usually a mobile phone, tablet or gateway) is connected with several peripheral devices (eg sensors, actuators). The central device is responsible for coordinating and managing the communication between all peripheral devices.
Mesh Topology: Mesh topology allows devices to communicate directly with each other without relying on a central device. This topology is suitable for complex environments such as large IoT deployments, where devices need to communicate with each other to share data and instructions.
related article：
Discuss Star Topologies and Mesh Topologies From Zigbee mesh And Blue mesh
BLE Connectivity Advantages
Low Power Consumption: The low power consumption of BLE makes it suitable for mobile devices and battery-operated devices, enabling long-lasting wireless connections.
Fast connection: BLE devices can establish a connection within milliseconds to achieve fast data transmission and response.
Flexibility: BLE supports different connection modes, so that developers can choose the appropriate topology according to the needs to meet the requirements of the application.
Reliability: BLE connection has certain anti-interference and error correction capabilities to ensure reliable data transmission.