Does anyone have any recommended designs to monitor the power input of a Pro Mini board (3.3v 8Mhz)? I have couple INA219 modules - is there anything more power efficient to simply sample the voltage without drawing the current all the time?
Do you mean measure battery voltage, in a battery powered project (bypassing the voltage regulator)? If so, just use the ADC and internal voltage reference, as described here: Secret Arduino Voltmeter – Measure Battery Voltage
But replace all the "1023" constants with "1024".
Oh yes OF COURSE - I had that code in my project but had it commented out when I tried couple other convoluted designs. Yes this works perfectly.