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What practical PCB layout tips are worth sharing?
It is one of the important links in the process, which has a vital impact on the performance and reliability of the product. When doing PCB layout, following the 3W principles can help designers
Better understanding of layout requirements leads to better board design. Industrial Router/Gateway This article will introduce the specific content of the 3W principle in detail and discuss its application in circuit board design.
1. The definition of 3W principle
The 3W principle refers to "Wiring, Worship, Waste", that is, the three aspects of wiring, power supply and waste. Among them, "connection" refers to the signal transmission lines on the circuit board, including signal lines, power lines, ground wires, etc.; "power supply" refers to the power lines on the circuit board, including power input, power filtering, power distribution, etc.; And "waste" refers to the waste of space on the circuit board, including board size, device layout, line direction, etc. The three areas are interrelated, and problems in one area will affect the other two areas. Therefore, following the 3W principle can help designers better balance the relationship between these three aspects in circuit board design, so as to design a better circuit board.
2. Wiring
Wiring refers to the signal transmission lines on the circuit board, including signal lines, power lines, ground lines, etc. When designing a circuit board, the layout of the wiring is a very critical part. Good wiring layout can improve the reliability and performance of the circuit, and reduce the noise and interference of the circuit. When making wiring layout, the following points need to be paid attention to:
1. The length of the signal transmission route should be as short as possible, which can reduce signal interference and transmission errors.
2. The width and distance of the signal transmission route should be selected reasonably to ensure the stable transmission of the signal.
3. Signal lines and power lines should be separated from each other to avoid power noise
impact on signal transmission.
4. The signal line and ground line should be separated from each other to avoid the influence of ground line noise on signal transmission.
5. The layout of signal transmission routes should avoid crossings and loops to reduce signal interference and transmission errors.
3. Power supply (Worship)
Power supply refers to the power lines on the circuit board, including power input, power filtering, power distribution, etc. The layout of the power supply is a very important part of the circuit board design. When making power supply layout, the following points need to be paid attention to:
1. The power input should be concentrated in one position of the circuit board as much as possible for power filtering.
2. Power filter capacitor
It should be placed as close as possible to the power supply pins to improve the filtering effect.
3. Power distribution should be as balanced as possible to avoid power noise and overload problems.
4. Power distribution and signal lines should be separated from each other to avoid the influence of power noise on signal transmission.
5. The power line and ground line should be separated from each other to avoid the influence of ground line noise on the power supply.
4. Waste
Waste refers to the waste of space on the circuit board, including board size, device layout, line orientation, etc. Single serial port server Waste is also an area of concern when designing a circuit board. When laying out, you need to pay attention to the following points:
1. The size of the circuit board should be as small as possible to reduce material cost and layout complexity.
2. The layout of the device should be reasonable to reduce the length and complexity of the wiring as much as possible.
3. The distance between devices should be reasonable to avoid signal interference and transmission errors.
4. The direction of the line should be simple and direct to reduce signal interference and transmission errors.
5. The use of space should be sufficient to avoid large blank areas on the board.
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How does the LoRaWAN network ensure the secure transmission of data
LoRaWAN technology is a wireless communication technology widely used in the fields of Internet of Things, automation control and industry. In these applications, data security is very important, so the design and implementation of the LoRaWAN network pays great attention to data security.
The LoRaWAN network uses a random access mechanism similar to the ALOHA protocol. Nodes send data at a certain rate in a specific time slot, and the base station responds after receiving the data to confirm whether the data is successfully received. The LoRaWAN network can adopt different data transmission methods, mainly including the following two:
Unconfirmed Transmission: The node does not wait for the confirmation after sending the data, but directly sends the next data. This method has the advantages of fast transmission speed, high efficiency, and low power consumption, but data transmission may be lost or repeated, and data reliability cannot be guaranteed.
Confirmed Transmission: The node waits for the confirmation signal from the base station after sending the data to ensure the successful transmission of the data. This method has the advantages of high reliability, and data is not easy to be lost or repeated, but it needs to increase communication time and power consumption, and the transmission efficiency is low.
Which transmission method to choose depends on the specific requirements of the application, and factors such as transmission efficiency and data reliability need to be weighed. At the same time, in the LoRaWAN network, measures such as encryption technology and key management can also be used to ensure data security.
LoRaWAN network security features mainly include the following aspects:
Data encryption: The LoRaWAN network uses encryption technology to encrypt the transmitted data to protect the confidentiality and integrity of the data. Commonly used encryption algorithms include AES, DES, etc.
Data integrity protection: The LoRaWAN network uses data integrity protection technology to ensure that data is not tampered with or lost during transmission. This includes techniques such as data checksums, data encoding, and more.
Data privacy protection: The LoRaWAN network also pays attention to data privacy protection to protect users' personal information from being leaked. This includes technologies such as user authentication, data encryption storage, etc.
Network partition: LoRaWAN network uses network partition technology to enhance the security of the network. The strategy of network partition includes node partition and link partition, which can improve the security of the network by reducing the potential attack surface.
Node security: The nodes of the LoRaWAN network also need to pay attention to security. Node security includes node authentication, node encryption, node data verification and other technologies to ensure that nodes are not illegally accessed and attacked.
In short, the design and implementation of the LoRaWAN network pays great attention to data security, using a variety of security technologies, such as data encryption, data integrity protection, data privacy protection, network partitioning and node security, etc., to ensure data confidentiality and integrity , privacy and availability. These security features help to protect user data security and privacy, improve network reliability and stability, and promote the development of the Internet of Things and automation control.
LoRaWAN gateway module product recommendation:
lorawan DTU gateway radio products:
Transmission power: 0.16W Communication distance: 3km
Product weight: 120g
Product size: 100*84*25mm
Product introduction: E78-DTU (900LN22) is a standard LoraWan node radio designed and produced by Ebyte. It is developed based on our E78-868/915LN22S module. The equipment supports EU868/IN865/RU864/US915/AU915/AS923/ KR920 has seven regional files; the device supports CLASS–A/CLASS-C node types, and supports ABP/OTAA two network access methods; the external communication interface of the station adopts RS485 and RS232 serial port communication, and the user can simply configure it through AT commands or the host computer Access to the standard LoraWan network, at the same time, the radio has the functions of transparent transmission, active polling, etc., supports serial port upgrade and remote configuration, and is an excellent choice for current IoT applications.
Ethernet - the composition and working principle of the network card
A Network Interface Card (NIC for short), also known as a network adapter, is a device that connects a computer to a local area network. As long as it is connected to a LAN, a network card needs to be installed. wireless communication A network card mainly includes the bottom two layers of OSI, the physical layer and the data link layer. The chip of the physical layer is called the PHY, and the chip of the data link layer is called the MAC controller. After an introduction (Ethernet - PHY, MAC and MII basics).
The network card works in the last two layers of OSI: the physical layer and the data link layer. The physical layer defines the electrical and optical signals, line status, clock reference, data encoding and circuits required for data transmission and reception, and communicates to the data link Layer devices provide standard interfaces. The data link layer provides functions such as addressing mechanism, data frame construction, data error checking, transmission control, and standard data interface to the network layer. The chip of the data link layer in the Ethernet card is called the MAC controller. These two parts of many network cards are done together. The relationship between them is that the PCI bus is connected to the MAC bus, the MAC is connected to the PHY, and the PHY is connected to the network cable (through the transformer).
Connect MAC and PHY through the standard MII interface defined by IEEE. This interface is defined by IEEE. The MII interface transfers all data and data control of the network. The MAC determines the working state of the PHY and controls the PHY by using the SMI (Serial Management Interface) interface by reading and writing the registers of the PHY. Part of the registers in the PHY are also defined by IEEE, so that the PHY reflects its current status into the registers, and the MAC continuously reads the status register of the PHY through the SMI bus to know the current status of the PHY, such as connection speed and duplex capability wait. Of course, you can also set the PHY registers through SMI to achieve control purposes, such as opening and closing flow control, auto-negotiation mode or mandatory mode, etc.
Therefore, whether it is the physically connected MII interface and SMI bus or the status register and control register of the PHY, there are IEEE specifications, so MACs and PHYs of different companies can work in harmony. Of course, in order to cooperate with some unique functions of PHYs of different companies, the driver needs to be modified accordingly.
When the PHY sends data, it receives the data from the MAC (for the PHY, there is no concept of a frame, for it, it is all data regardless of the address, the data is still CRC), and every 4 bits add 1 bit of error detection Code, and then convert the parallel data into serial stream data, and then according to the coding rules of the physical layer (NRZ coding of 10Based-T or Manchester coding of 100based-T), the data coding is converted into an analog signal and sent out. The process of receiving data is reversed.
When a CMOS process chip is working, the signal level generated is always greater than 0V (this depends on the process and design requirements of the chip), but such a signal will have a large DC voltage when it is sent 100 meters or even farther away. weight loss. Moreover, if the external network cable is directly connected to the chip, electromagnetic induction and static electricity can easily cause damage to the chip.
Furthermore, the grounding method of the equipment is different, and the different grid environment will cause the 0V levels of the two parties to be inconsistent. In this way, the signal is transmitted from A to B. Since the 0V level of A equipment is different from the 0V level of B point, this will cause a large current. Flow from a device with a higher potential to a device with a lower potential. At this time, Transformer (isolation transformer) is needed. It filters the differential signal sent by the PHY with a differential-mode coupled coil coupling filter to enhance the signal, and couples it to the other end of the network cable through the conversion of the electromagnetic field. In this way, there is no physical connection between the network cable and the PHY and the signal is transferred, the DC component in the signal is cut off, and data can also be transmitted in devices with different 0V levels.
The isolation transformer itself is designed to withstand the voltage of 2KV~3KV, and at the same time it plays the role of lightning protection. Some users' network equipment is easy to be burned out in thunderstorm weather, most of which are caused by unreasonable PCB design, and most of them burnt the interface of the equipment, and few chips are burned, because the isolation transformer plays a protective role.
When sending data, the network card first listens to whether there is a carrier on the medium (the carrier is indicated by the voltage), WLAN communication technology and if there is, it thinks that other stations are transmitting information and continues to listen to the medium. Once the communication medium is quiet for a certain period of time (called the inter-frame gap IFG=9.6 microseconds), that is, it is not occupied by other stations, frame data transmission is started while continuing to listen to the communication medium to detect collisions. During the transmission of data, if a collision is detected, the transmission is stopped immediately, and a "block" signal is sent to the medium to inform other stations that a collision has occurred, thus discarding the corrupted frame data that may have been received, and waiting A random amount of time (CSMA/CD's algorithm for determining the waiting time is a binary exponential backoff algorithm). Wait for a random amount of time before making a new send. If a collision still occurs after multiple retransmissions (greater than 16 times), the transmission is abandoned.
When receiving, the network card scans each frame transmitted on the medium, and if it is less than 64 bytes in length, it is considered a collision fragment. If the received frame is not a conflicting fragment and the destination address is a local address, check the integrity of the frame, if the frame length is greater than 1518 bytes (called an oversized frame, it may be caused by a wrong LAN driver or interference) or If it fails to pass the CRC check, it is considered that the frame is distorted. Frames that pass the verification are considered valid, and the network card receives them for local processing.