Analog-to-Digital Converter (ADC) samples a analog signal and provides a digital value corresponding to it, which can be processed by a software.

ZDev provides APIs to read samples from ADC channels. The API supports value scaling. If an 8-bit value (range 0x0 - 0xFF) is written using the adc_write8() API and the underlying ADC Hardware is 12-bit, the value is scaled up to 12 bits. Similary if a 16-bit value (range 0x0 - 0xFFFF) is written using the adc_write16() API and the underlying ADC is 12-bit, the value is scaled down to 12 bits.

The ADC functions are declared in adc.h. The no. of available ADC channels is indicated by the constant ADC_NCHANNELS. The following example glows an LED if the voltage on the ADC channel 0, is greater than Vref / 2.

Comparator. 

#include <board.h>
#include <adc.h>

#define OFF 0
#define ON  1

int main()
{
        uint8_t val;

        board_init();
        adc_init(); /* Initialize the ADC. */
        adc_enable(0);

        gpio_init();
        gpio_enable_pin(LED1_GPIO);
        gpio_direction_output(LED1_GPIO, OFF);

        while (1) {
                /* Read an 8-bit sample from the ADC channel 0. */
                val = adc_read8(0);
                if (val > 128) {
                        gpio_set_pin(LED1_GPIO, ON);
                }
        }
}