Can you tell from the circuit why those values were chosen for the voltage divider?
The R2 & R3 divider is used to reduce the output voltage to a range the MCU analog input can handle. That is a common technique and separate from the output voltage control part.But using the datasheet= 10+8/10(1.275). But, that is not right
Being only a hobbyist, I'm still do not understand 100% why they chose the resistor values of 10k and 8k, is it to keep it around theiddle range of vdd about 2.5?
Simpler than that - 10 is twice 5(volts), so the 8 is twice 4(volts), giving a total of 9V - no calculation really required, just look at the values.And that would be calculated simply by the out put of the regular multiplied by the voltage divider 10+8/10?