Decode ADC Result Using Union Bitfields

Code

#include <stdio.h>
#include <stdint.h>

typedef union {
    struct {
        uint16_t adc_value : 12;
        uint16_t channel   : 4;
    };
    uint16_t adc_reg;
} ADC_Result;
ADC_Result r;
int main() {
    uint16_t reg;
    scanf("%hx", &reg);
    r.adc_reg = reg;
    // Fill union and print channel and adc_value
    printf("Channel: %d\n",r.channel);
    printf("ADC Value: %d",r.adc_value);
    return 0;
}

Solving Approach

1. Define a union that overlays:
   • A raw 16-bit uint16_t adc_reg
   • A struct with:
     • adc_value (12 bits)
     • channel (4 bits)
2. Read adc_reg from input
3. Extract and print:
   • Channel number
   • ADC result (0–4095)