There seems to be a design/manufacturing fault with the Shelly 2.5 where some of the component legs on the back of the circuit board haven’t been trimmed after soldering. This allows them to touch the Wi-Fi antenna which is stuck to the inside of the case. The antenna has an insulating film on it, but a small amount of pressure on the case will puncture the insulation and cause problems like these:
(These aren’t my photos, they are taken from the internet).
If I bought one of these the first thing I would do is to pop the cover off and take pair of snips to legs of the blue connector block pins, and to the pins in the top right hand corner of these photos.
Infact, although I’m a fan of the Shelly products, I’ll probably steer clear of the 2.5
As far as GPIOs are concerned, these are now quite well documented on the internet.
With the Shelly 1 I’ve found that there is a problem if you try to use interrupts to sense switch operations, as documented here:
I’m not sure if the 2.5 is the same or not.
Although I’ve hacked quite a lot of hardware devices in the past and happily control them with my own firmware, I’m not sure that there is as much need now, as Tasmota seems to the the De Facto way to go now.
Obviously linking Blynk and Tasmota isn’t that easy without some additional hardware/software, but as I use MQTT and Node-Red then that part is already there for me.
If you want to do power monitoring then I’d say Tasmota is definitely the way to go.
Pete.