How to estimate battery voltage in STM without extra component
Thank you for your replies.
But I find the solution. There is an internal 1.2v voltage reference in STM32 microcontrollers called 'VREFINT'. This voltage can be measured from channel 17 of ADC1. Reference of conversion is VDDA that is connected to VCC of circuit. So we can calculate VCC of circuit with the value of converted 'VREFINT'.