I'd like to change many thing a embedded screen that runs on GPM4730 SoC http://www.generalplus.com/rmf/GPM4730AV01_ds.pdf
Based on the datasheet, it's an ARM Cortext-M4.
I have the original firmware https://p10.secure.hostingprod.com/@site.ambientweatherstore.com/ssl/ws2000/user.bin
And also found this PDF about hacking Xiomi bridge: https://dontvacuum.me/talks/DEFCON26-IoT-Village/DEFCON26-IoT-Village_How_to_Modify_Cortex_M_Firmware-Xiaomi.pdf
But I don't really know where to go from here. I would like to add a service to upload data to for instance. Or change the layout of what is shown on the screen.