ESP8266 NodeMCU development board connects to mobile phone hotspot issues
Foreword:
As we all know, esp is one of the right assistants in constructing an IOT project, in layman's terms: "WIFI module"
But the following is about the NodeMCU development board in esp8266 , its function is more than just a simple WiFi module.
The course I am watching here is a video produced by the Tai Chi maker team. It is very friendly to the basic Xiaobai. Students who are interested can learn it. The following is the connection to station B: [ESP8266 Tutorial] Zero-based introductory learning materials Networking-Basic Knowledge (Tai Chi Maker Team)
Closer to home, this blog will not talk about technology, not introduction, but a problem that I actually encountered when actually operating the NodeMCU development board, and I haven’t found it after searching on the Internet for a long time, but I’m smart , And solved it.
Problem Description:
For the majority of makers, I believe that many friends choose their own mobile phone hotspots when connecting the NodeMCU development board to WiFi, but you will find that when the source code of the leveled WiFi is burned into the NodeMCU version, it is actually connected Can't get the WiFi of the phone? What is going on here?
So I used my powerful search ability and found that this mobile phone hotspot is also very knowledgeable.
Mobile phone hotspot frequency band:
The current mobile phone hotspot frequency bands have both 2.4GHz and 5Ghz, just like routers. You may choose the 5GHz frequency band when you turn on WiFi, saying that you can increase the speed of the hotspot, but then, do you really understand these two frequency bands?
Here I shamelessly asked Du Niang: What is the difference between 2.4GHz and 5GHz on mobile hotspots?
The following is Du Niang's official answer:
1. Different frequency bands
1. 2.4GHz: Working in the 2.4GHz frequency band can obtain a larger range of use and stronger anti-interference ability, which is widely used in household and commercial fields.
2. 5GHz: refers to Wi-Fi operating in the 5Ghz radio wave frequency band and adopting the 802.11ac protocol.
2. Different features
1. 2.4GHz: The overall bandwidth is better than other ISM frequency bands, which improves the overall data transmission rate, allows system coexistence, allows two-way transmission, and has strong anti-interference and long transmission distance.
2. 5GHz: The entry-level speed of 5G Wi-Fi is 433Mbps, which is at least three times the speed of Wi-Fi. Some high-performance 5G Wi-Fi can reach more than 1Gbps.
3. Different advantages
1. 2.4GHz: 2.4GHz frequency band is a universal frequency band in the world, while 868MHz and 915MHz are ISM frequency bands used in the United States and Europe. The introduction of these two frequency bands avoids the mutual interference of various wireless communication equipment near 2.4GHz .
2. 5GHz: It adopts a chip that works at a frequency of 5GHz, which can simultaneously cover the two major frequency bands of 5GHz and 2.4GHz. In addition to being faster, it can also improve the problem of small wireless signal coverage.
Reference source: Baidu Baike-5G WiFi
Reference source: Baidu Baike-2.4ghz wireless technology
To put it simply, 2.4GHZ has strong wall penetration capability, slow network speed and high latency. 5GHZ basically cannot penetrate the wall, the network speed is fast, and the delay is low.
problem solved:
Huh~, if you think about it carefully, does your NodeMCU also have a 2.4Ghz ?
Having said that, combined with the picture below, I believe that all friends on the Internet have suddenly realized it! 
Just change the frequency band of WiFi on your phone to 2.4GHz to connect normally!
Afterword:
Now think about it, when I played Raspberry Pi, I often failed to connect to the hotspot of the mobile phone. Could this be the reason? So I hurried to try it, and found that it was really stable after the mobile phone hotspot was changed to 2.4GHz, and it could be connected every time.