A small PCB that can display the status of the relay, it connects to it through a 5 pin cable. A reset switch is also provided. You can also program/flash the relay through it, there is a separate header for programmer connection.
- BTT Relay v1.2 https://github.com/bigtreetech/BIGTREETECH-Relay-V1.2
- Custom firmware with platform.io https://github.com/galagithub/btt_relay_os