# 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
- `GPIO2`: relay output
- `GPIO4`: MAX6675 SCK
- `GPIO5`: MAX6675 CS
- `GPIO6`: MAX6675 SO

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

## Fixed control timing
- PWM/control loop window: `1800ms`
- Control tick: `200ms`