A flame sense circuit and method utilizing only a single pin of a microcontroller is provided. A flame sense circuit is used to vary the charge on a capacitor from a logic high indicating no flame to a logic low when a flame is detected. The microcontroller changes the state of the pin coupled to this circuitry from a high impedance input to detect when the capacitor is discharged indicating the presence of flame, to a logic high output to recharge the flame sense capacitor. Once this charging has been accomplished, the microcontroller again changes the status of the pin to a high impedance input and verifies that the capacitor has been charged. This pin is monitored to verify that the flame sense capacitor is again discharged to indicate the continued presence of flame. This process is repeated to ensure flame continues to be present during a combustion event.