Hello guys,
thank you for your intels ! i recieved the pcb and built it, it works
i changed C1 for a 0.1µF, and removed R12
i kept the resistor bridge for isp comm.
i tried to activate buffer with irq but it's going rogue, gave up with that
i doubt that the inclusion button has any utility, it seems to be just an other reset button
It gives me a little serial gateway wich size is about the same as a "sonoff zigbee dongle plus"
i'll have to make an enclosure for it now