ESP8266EX Tiny WIFI Board

Based on the 2.4GWIFI development board of ESP8266EX, all IOs are led out, and everything that should be pulled up and down is pulled up and down. The RF part works well, and the automatic download is OK.
Using the program download script of Espressif's official SDK, it can run to 2.86Mb/s (baud rate 300000 ), the download speed is quite fast (see video).
It is only slightly larger than the common ESP8266 module package. It should be the smallest full-featured ESP8266 development board currently.
 
One thing to note is that the IPEX seat cannot be welded, which will be discussed below.
 
The reason is that I need to implement some functions for STM32 networking for another project, but after searching around the modules on the market, none of them meet my requirements.
It is convenient to use modules, but the modules do not support quick disassembly, and some peripherals need to be added. circuit to achieve interaction with the existing hardware system.
Most of the modules on the market use 2~8M Flash, which does not meet the project requirements. The most important thing is that the module is too ugly and does not suit my taste at all.
 
In short, the requirements are that it is small and good-looking, has a large Flash capacity, has automatic downloading, two sets of serial ports and IO leads, and can be quickly disassembled. The key point is that it is small and good-looking.
 
So I tinkered with such a small board while referring to Espressif's official design guide. Compared with other common modules, it uses a smaller package.
It turns out that Flash does not need to be larger than the main control chip. The CH343P is also much smaller than the silly, big, black and thick part of the CH340. The most troublesome
part of the whole project is the RF impedance matching part, which is quite fiddly. The official design guide states that the antenna matching impedance needs to be 39-j6Ω.
RF impedance matching is quite mysterious. , if I don’t pay attention to the impedance mismatch, I can’t connect to WIFI. The goal is miniaturization and I can’t completely
refer to the official PCB design. I almost vomited just to run the simulation on this small board. (It takes a long time to run the simulation on this piece of shit. More than 6 hours)
Finally, I borrowed a network analyzer to fix it. Fortunately, the result was that the OK
PCB project would report a DRC error. It looked like the LNA was short-circuited to ground, but in fact it was not. Due to the characteristics of the RF circuit This is what it looks like.
Just ignore DRC errors (so when can Lichuang turn off the DRC check of specified components). The energy trend of the RF antenna is like this: As for why the IPEX seat cannot be welded, it is because the impedance of the feeder changes after welding, and the energy will Concentrated on the lump under the IPEX seat,
it will generate heat as if it is short-circuited, and then the WIFI cannot be connected. The IDF debugging error reports that wifi state b0 -> 200 cannot be connected normally. I have tried to re-match the seat impedance,
but this thing is It’s really metaphysics, no matter how I try it, I can’t get it right, so I simply changed the version and removed the socket, but it only caused more problems, so the socket can only stay here and become part of the radio frequency circuit (this project is based on Metaphysics bug is running, don’t modify it! Don’t modify it!)
Of course, friends who have the ability to modify it can share it~
 
The field source radiation report looks weird (a bit like that), but the signal is relatively OK. I’m confused about what it looks like. Anyway, this board can’t be seen with the naked eye.  
In fact, it can be made smaller. First, the buttons and LEDs can be removed. If the IO is not used, the long seat can be removed. The CH343P chip comes with
a 3.3V reference voltage. Use it directly to convert USB5V to 3.3V, saving an LDO, but its output is only a pitiful 40mA.
In addition, the automatic download circuit does not need to use those transistors. The early automatic download circuit was directly connected to RTS and DTR, which can Reference here: https://www.esp32.com/viewtopic.php?t=5731#p24882
 
Finally, here is a photo of the project. The board has been fully verified. Feel free to build the board because it involves radio frequency circuits and the components are relatively compact, so The soldering
suggestion is to open a steel mesh and add a teppanyaki. Brother Fu, I turned 50 and then turned left to SMT. I tried the challenge of sticking a board by hand with the blade of a knife. It took me three hours of fiddling. Fortunately,
it was a white PCB that could be used. It turned yellow because of the rosin in the soldering oil. Well, it’s not that it can’t be used, right? You can say that I’m someone who has pasted QFN and 0402 on my hands :P