adolfbasil

  

ZigBee technology is a two-way wireless communication technology with short distance, low complexity, low power consumption, low speed and low cost. It is mainly used for data transmission between various electronic devices with short distance, low power consumption and low transmission rate, as well as typical periodic data, intermittent data and low response time data transmission applications. Since the invention of radio by Marconi, wireless communication technology has been developing in the direction of continuously increasing data rate and transmission distance. For example: the purpose of the third-generation mobile communication network (3G) within rs232 over wifi the wide area network is to provide multimedia wireless services, and the standards within the local area network range from 1Mbit/s of IEEE802.11 to 54Mbit/s of IEEE802.11g. The ZigBee technology, which has been widely studied at present, is dedicated to providing a low-speed wireless communication technology with extremely low complexity, cost and power consumption for fixed, portable or mobile devices. This wireless communication technology has the following characteristics:

Low power consumption: In the working mode, ZigBee technology has a low transmission rate and a small amount of transmitted data, so the signal sending and receiving time is very short. Secondly, in the non-working mode, the ZigBee node is in sleep mode. The device search delay is generally 30ms, the sleep activation delay is 15ms, and the active device channel access delay is 15ms. Due to the short working time, low power consumption of sending and receiving information and the use of sleep mode, the ZigBee node is very power-saving, and the battery working time of the ZigBee node can be as long as 6 months to 2 years. At the same time, because the battery time depends on many factors, such as: battery type, capacity and application occasions, ZigBee technology has also optimized the use of batteries in the protocol. For typical applications, alkaline batteries can last for several years, and for some cases where the ratio of operating time to total time (on time + sleep time) is less than 1%, the battery life can even exceed 10 years.

Reliable data transmission: The media access control layer (MAC layer) of ZigBee adopts a talk-when-ready collision avoidance mechanism. Under this fully confirmed data transmission mechanism, when there is a need for data transmission, it will be transmitted immediately. Each data packet sent must wait for the confirmation message from the receiver and reply to the confirmation message. Indicates that a collision has occurred and will be transmitted again. Using this method can improve the reliability of system information transmission. At the same time, dedicated time slots are reserved for communication services requiring fixed bandwidth, which avoids competition and conflict when sending data. At the same time, ZigBee is optimized for delay-sensitive applications, and the communication delay and sleep state activation delay are very short.
  

In today's smart age, no house, no car, no woman can endure, but if you really say that you go out without a wireless network, you will be like a dead body, and the whole person will lose his energy.

Someone told Brother Ma that you can turn on the data? Brother, you are so smart, but Brother Ma is a grass-roots citizen, rs485 wifi so he can turn on 4G when he has nothing to do when he goes out. I'm afraid he won't be able to wear his pants in two or three days. Get up, can't hurt!

So what should I do? The little four brothers gave me a trick, not to mention it is really useful. Next, let’s see what a good trick is with the code brother. In fact, you only need to prepare a portable wireless WiFi on it.

So, what is a portable wireless WiFi? A portable wireless WiFi is a mobile wireless WiFi receiving and transmitting signal source formed by the wireless Internet access chip provided by the wireless operator. Mobile WiFi. This portable wireless WiFi is very good for traveling or working.

Portable wireless WiFi, small and convenient to carry, good signal, fast Internet access, smooth and slow battery life, can help us have a high-speed Internet experience anytime, anywhere. With the development of today's society, portable wireless WiFi is not only getting better and better, but its performance has also improved a lot!  

When the sender assembles the message, it combines several small packets into one packet, so that the receiver cannot parse out the small packets. This corresponds to Nagle's algorithm. Because both TCP and Nagle's algorithm are products of the last century, doing so in early networks can significantly reduce network stress. Otherwise, sending small packets with only a few bytes frequently will seriously waste network IO performance.
However, in the modern Internet, the network performance has been greatly improved. It seems that the IO performance improved by the Nagle algorithm is not so important. On the contrary, due to the operation of waiting for the data to be merged, the transmission delay will become larger. In the application of online games , it will greatly affect the experience. So it is generally turned off now.
Bluetooth Module

After the receiving end receives the message, the application layer cannot always take the data immediately, and there is always a receive buffer. If the interval between two independent messages entering the buffer is too small, the application layer cannot take the previous message in the middle of the two messages, then the next time it is read, the two packets of messages are bound to be read at the same time, which will also lead to sticky packets.serial module


And this situation cannot be avoided by letting the sender send packets evenly in time, because of the existence of network instability, even packets sent evenly in time may appear randomly to the receiver.