Hongmeng Bluetooth keyboard expansion module

This project is an integrated and improved version of the Hongmeng Bluetooth keyboard solution released by Runhe.

The original plan is to combine modules + Dupont lines. As a rookie who can draw PCBs, I think it is necessary to upgrade.

• The entire solution has been verified. Keyboard input can be obtained on the m40p (5G). We will check the effect on the computer later. Although it has not been verified, there should be no problems.
• After the whole board is connected to the battery and tested, the current of the board is about 200mA. The test conditions are measured by the 2.4G receiver connected to the USB-A port (as shown below) and are not used as a reference for the power consumption of a directly connected keyboard.
• Main references: WCH chip manual, IP5407 chip manual, Neptune Bluetooth keyboard solution documentation, related design demos in the Lichuang EDA open source community, etc. I would like to express my gratitude to these open source masters. Without your selfless sharing, I would not be able to make it.

advantage:

1. It avoids the previous trouble of using DuPont wires to connect small modules, and all functions are integrated into one PCB.
2. The onboard lithium battery charging, discharging, 5V boost and charge and discharge protection can be used by connecting a bare battery.
3. The battery is not designed on the board, and the capacity can be selected according to actual needs.
4. Type-C can charge lithium batteries and can also be used as an external power supply interface. With external power supply, the battery does not need to be connected.
5. Type-C has an integrated download function. If new official firmware is released, the firmware can be updated.
6. You can directly use a download tool from Lianshengde to update the firmware, and you do not necessarily have to use Device Tool.

The board is now 68mm wide and 40mm high. The Neptune module, CH9350L chip, CH340E chip, Yingjixin charging chip IP5407 and battery protection chip IP3012 are laid out on the front. The type-c socket, input protection circuit and USB-A are laid out on the back. base, a switch, and two buttons.

Now the question:

1. Now we have just completed the verification of the plan. The difference between the actual product and the design is still limited by the materials on hand and the flying wires on the board, so the actual product does not look good.
2. The board is still relatively large and needs to be made smaller.
3. Currently, only the first version of the firmware can be used. Both firmwares 0.2 and 0.3 are not working yet. The reason has not yet been found out.
4. Some of the material selections are unreasonable. Some choose large ones, and some choose small ones. There is still room for continuous optimization.

There will definitely be a follow-up to this project, so please continue to pay attention.