okay. don't know how to comment on github.
The bluetooth module in alphax is definitely a BLE device (bursts of data, rather than old-style SPP profile)
After you connect it to the MCU, (MCU's TX to WL9981TC RX, MCU's RX to WL's TX, Paragraph 4 of the datasheet), after power up you should see 'READY!' message on the MCU, meaning that Initialization is completed, connection is allowed, and the module is ready for pairing.
If your Windows PC supports BLE, I suggest using something like
https://www.nordicsemi.com/Products/Development-tools/nRF-Connect-for-desktop
When you launch it, you should see the module in advertising mode. After you choose it and hit 'connect' button, you'd see 'Connect!' message on the MCU side. If I understand chineese correctly, PIN5 should go HIGH when there is a connection between the module and the PC/mobile. After this, you can probably start sending and receiving messages.
default settings (for the MCU side) should be 115200, 8N1 with no flow control.
"To ensure complete data transmission, each data packet sent by the HOST is required to be less than or equal to 256 bytes, and the sending interval is greater than or equal to 2ms." - don't know what this means. splitting binary file into chunks?
Keep in mind that as long as the Bluetooth device is in a disconnected state, this Pin 5 always outputs a low level.
A nice find, by the way, but almost no electrical specifications in the datasheet (consumption at various states)