IronOS is embedded firmware for a family of portable soldering irons (TS100, TS80/P, TS101, Pinecil, Pinecil V2, MHP30, Sequre S60/S60P/T55/S99). The firmware runs on three distinct SoC architectures — STM32F103 (Cortex-M3), GD32VF103 (RISC-V), and Bouffalo BL702 (RISC-V) — behind a single board-support abstraction. It implements PID temperature control of the soldering tip via PWM, thermocouple uV-to-temperature conversion with cold-junction compensation, USB-PD (FUSB302/FUSB302B/HUB238/FS2711) and Quick Charge 3.0 power negotiation, accelerometer/hall-effect-based motion detection for sleep, an OLED menu UI, and a full BLE GATT stack on Pinecil V2. The core control loop is: ADC samples tip thermocouple voltage (with PWM holdoff timing) -> gain/op-amp compensation and lookup-table interpolation to Celsius -> PID controller -> PWM duty to the heating element, with input voltage/current monitoring for wattage budgeting and thermal runaway protection.