This paper discusses an adaptive Maximum Power Point Tracking (MPPT) control involving minimum computing effort, suitable for implementation with low cost microcontrollers. The runtime multiple optimal setup of the Perturb&Observe MPPT algorithm, is achieved by exploiting the correlation existing among the MPPT efficiency and the onset of a permanent 3 level quantized oscillation around the MPP. As no operations on measured voltage, current and power are required, the adaptive MPPT control is achievable with very cheap digital devices. Experimental test results are presented in the paper, regarding a 70W LED lighting system fed by a photovoltaic source, including a energy storage device.