Analog-to-Digital Conversion

Turning a voltage into a number.

An ADC measures an input voltage and returns an integer. A 10-bit ADC gives 1024 steps, so with a 5 V reference each step is about 4.9 mV.

The formula is: voltage = reading x reference / (2^bits). A noisy or high-impedance source gives unstable readings; average several samples and keep wires short.

Never feed an ADC pin more than its supply voltage.

uint16_t raw = adc_read(2);            /* hypothetical call, channel 2 */
float volts = raw * 5.0f / 1024.0f;    /* 10-bit, 5 V reference */