not really an issue but ...
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it would be nice to have some explanation about the function around PB1 - R/C filter/integrator - U2 - R11..R15/D4 - Vsense. I looked at the "homepage", found good explanation about mppt, but none about theory behind "feedback/control" circuitry.
The R/C filter network provides a stable and low noise reference voltage for the V+ input of the OP-Amp, which is controlled by the PWM output of the µC. Since the OP-Amp has no symmetrical power supply, a bit of trickery at the voltage divider is necessary to put the PWM signal of the µC, which can not exceed 3.3 V, to a level that is high enough about GND to be compared by the V- input of the OP-Amp, which is connected to the solar input rail via a voltage divider. If the V+ input is greater than the V- input of the OP-Amp, the input solar voltage is lower than the set MPP point. The output of the OP-Amp goes up, signalling the DC/DC buck controller chip MC33063 via its reference pin that the set output voltage has been exceeded. In response, the MC33063 will reduce the pulse-pause-ratio of the PWM in the MC33063, hence the current load on the solar module will go down and the solar input voltage rises to the point where V- at the Op-amp becomes greater then V+. V out of the OP-Amp goes down: So here we have a control loop, controlling the MPP voltage.
By controlling the PWM output of the µC, the MPP input voltage can be controlled by the µC firmware.
thank you for the quick answer.