#The4thStartupContest#STC-NUCLEO

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  Briefly introduce the work: 18650 powered STC offline downloader and STC8A8K emulator development board.
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  1. Work details;
  This is an STC offline downloader that integrates the STC8A8K most powerful 51 microcontroller and 18650 lithium battery power supply. It can realize offline and online downloading of external STC51 microcontrollers, power supply of external target boards, and real-time simulation of 51 microcontrollers with the STC8A8K on the board. The IO of the microcontroller has a pull-up LED to display high and low levels. The LED power supply can be turned off with a dip switch. The built-in microcontroller on the board can also be connected and disconnected with a dip switch. The built-in 18650 battery can be used for mobile offline downloading. It is made according to the open source circuit of STC company. All are open source. Welcome to use it!
  2. Describe the challenges faced by the work and the problems solved;
  This design is an integration of several open source projects of mine (STC offline downloader + 18650 battery boost 5V board + STC8A8AK emulator board). All hardware problems are solved in those open source projects. The links to other open source projects are as follows:
STC51 MCU offline downloader https://diy.szlcsc.com/p/583703056a/stc51-dan-pian-ji-tuo-ji-xia-zai-qi
18650 boost 5V board https://maker.lceda.cn/p/583703056a/18650-sheng-ya5v-ban
STC8A8K MCU Emulator Board https://maker.lceda.cn/p/583703056a/stc8a8k-dan-pian-ji-ban
But this is also the second version. When designing the first version, I was always worried that the current in the power supply would be large, so I used window tinning in the circuit wiring. But after making the board, I found that this was redundant. It didn't look good to put several LED power supply control switches on the front, so I moved them to the bottom layer. The battery power supply allows the switch to use a side dial. It was found that it was easy to be touched by other objects and accidentally turned off the battery power supply. This time I used a direct plug-in dip switch. The reset pin of the STC microcontroller is a reused pin that can be used for reset or IO. This time I added a pin header with a short-circuit cap for switching. This time I used Jiali Chuang SMT patches. After I pasted them back and soldered the other parts myself, I found that the offline function could not be used after using 18650 batteries. I carefully found that I had selected the power supply isolation diode as an ESD bidirectional diode. After replacing it, the function was normal. Below are photos of the first version of the PCB and the new version of the ESD diode:
   This design is based on the open source circuit schematic and software of STC. For offline downloader software burning and motherboard upgrade, please follow the description of my other open source project to successfully https://diy.szlcsc.com/p/583703056a/stc51-dan-pian-ji-tuo-ji-xia-zai-qi
However, please pay attention to the upgrade pads in the red circle in the figure below. Because upgrades are not often used, dip switches are not used. If you need to upgrade, please use a 470 ohm resistor or tin to short-circuit. Please solder it open after the upgrade.
  Detailed BOM is in the project attachment
* 6. Demonstrate your work and record it into a video and upload it; (The video content must include: work introduction; function demonstration; performance test; close-up of the competition logo on the PCB, otherwise it will be deemed as giving up the competition)
Video link: https://v.youku.com/v_show/id_XNDMzNDk1MTI1Mg==.html?spm=a2h3j.8428770.3416059.1
7. Open source documents.
  All open source
https://lceda.cn/editor#id=|4edadcf117654bbe896e861efb74afc1|4ff8e71797b44be49b32c1346f8f07ec|1901c34636f14771bdda56ca28bf2168