Connect the button or sensor between the emergency input and GND. It triggers on a low level: GPIO35 on ESP32 DevKit or GPIO48 on ESP32-S3.
When triggered, Samovar switches off the heating, the water supply, the take-off and the stirrer, and blocks a restart until the board is rebooted. Several normally open buttons and sensors can be wired in parallel. For ESP32 DevKit, use the PlatformIO environment Samovar_alarm_button or add #define USE_ALARM_BTN to user_config_override.h. In the Samovar_s3 environment the GPIO48 emergency input is already enabled.
On ESP32 DevKit the emergency input is GPIO35; on ESP32-S3 it is GPIO48. In both cases it triggers when the input is shorted to GND.
For GPIO35 on the classic ESP32, an external 10 kOhm pull-up resistor to +3.3 V is required: pins GPIO34–39 have no internal pull-up. For GPIO48 on ESP32-S3, the firmware enables the internal pull-up.
On the Samovar 1.3.2 board, the emergency button connector is labeled ALRM_BT (older materials also call it ALARM_BTN). It is connected to GPIO35 and must have a 10 kOhm pull-up resistor to +3.3 V.
