Redmi-2A: Redmi 2 2A power supply module + 2.4/5G dual-band module

This module, designed to replace the battery of a Redmi 2A, expands the Klipper
circuitry to support RTL8821/8811CU 2.4/5G dual-band modules
 
. I recently came across Klipper while assembling a 3D printer.
Because the Redmi 2A doesn't support 5G Wi-Fi, and my home 2.4G network suffers from severe interference and extremely slow speeds, I developed this board.
 
The board's design is based on another open-source post on the forum: https://oshwhub.com/umekoko/hong-mi-2-gong-dian-xiao-ban-mp1584en
, with a redesigned layout.
I fixed some issues, including equalizing the length of the USB differential cables and using a switch to control the USB signal source.
The power circuit in the referenced post had a problem, presumably outputting 5V battery voltage.
After correcting this, testing showed that the 1117 output current couldn't power the Redmi 2A, causing continuous restarts. Testing confirmed it could directly use 5V power, so the 4.2V LDO was removed in the latest version.
 
The firmware is based on https://gitee.com/meiziyang2023/hm2-ubuntu-ports
, replacing the 6.10 kernel to support 8821/8811CU and repackaging it.
Firmware address: https://github.com/Rjgawuie/Redmi-2A-Klipper
. See the repository's Readme for flashing instructions.
 
Regarding component selection:
Purchase the components as shown in the attachment at the end of this document.
Note that there is an SOT23-3 packaged component on the small board at the front; you will need to remove it from the original battery protection board.
Regarding the RTL8821/8811CU module, be sure to buy the package shown in the image below, the USB interface type; do not mistakenly buy the SDIO interface type.
 
Finally, here are some photos of it running: