# Hardware Spec (ESP32-C3 Single Nail)

## Controller
- MCU: ESP32-C3, 160MHz, 4MB embedded flash.
- USB: native USB Serial/JTAG.

## Sensors / Actuation
- Thermocouple frontend: MAX6675 (K-type).
- Relay: SSR/mechanical relay, active HIGH.

## GPIO
- `D10`: relay output
- `D9`: MAX6675 SCK
- `D8`: MAX6675 CS
- `D7`: MAX6675 SO

## Safety defaults
- Max temp cutoff: `800F`
- Idle shutoff: `30 min`
- Near setpoint band for idle: `+/-8F`

## Control timing
- Adjustable via API/UI (`loop_size_ms` and `sleep_time`)
- Default profile is responsive (`1800ms` loop window, `0.2s` tick)