Hi Kamesh, adapt this... The duration of conversion is aroud 47uS. With 12dB attenuation, you can measure up to 4 volts ( a bit more...)

Have fun....

uint16_t data;

enum adc1_pad {
ADC1_GPIO36 = 0,
ADC1_GPIO37,
ADC1_GPIO38,
ADC1_GPIO39,
ADC1_GPIO32,
ADC1_GPIO33,
ADC1_GPIO34,
ADC1_GPIO35 ...