A wireless transmitter wirelessly charges/powers a wireless receiver. The transmitter performs an analog ping to tentatively detect a device. During an energizing phase of the analog ping, the transmitter applies power pulses to a resonant circuit within the transmitter, where, after application of the power pulses, the resonant circuit enters a free-resonance state of a resonating phase of the analog ping that follows the energizing phase. During the resonating phase, while the resonant circuit is in the free-resonance state, the transmitter samples voltage within the resonant circuit to generate one or more voltage-level samples. The transmitter processes the voltage-level samples to tentatively detect the device. If a device is tentatively detected then the transmitter performs a digital ping to definitively determine whether the device is present. If definitively detected then the transmitter wirelessly charges/powers the wireless receiver.