How to implement "Service Change Characteristic" on micropython

[amplatzer]

Background: my ESP32 device advertises two BLE signals in turn. But the iOS device can only discover 1 of them, until it connect to the the peripheral.

I found this. https://developer.apple.com/forums/thread/72343
https://stackoverflow.com/questions/73514239/how-do-i-use-the-service-changed-characteristic-to-invalidate-attributes-cache

Looks like Service Change is the thing I missed in my code, but I can't find an example how to implement this. Like should I create service 0x1801 and add characteristic 0x2A05, what FLAG do I need, and how to set the data (the range).

Can someone help, thanks.