Macro-Based Register Config Helper

Code

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

/* Field positions */
#define ENABLE_POS  0
#define MODE_POS    1
#define SPEED_POS   3

/* Field masks */
#define ENABLE_MASK 0x1
#define MODE_MASK   0x3
#define SPEED_MASK  0x7

/* Macros to set fields */
#define SET_ENABLE(val)  (((val) & ENABLE_MASK))
#define SET_MODE(val)    (((val) & MODE_MASK)   << MODE_POS)
#define SET_SPEED(val)   (((val) & SPEED_MASK)  << SPEED_POS)

uint16_t build_register(uint8_t enable, uint8_t mode, uint8_t speed) {
    return SET_ENABLE(enable)
         | SET_MODE(mode)
         | SET_SPEED(speed);
}

int main() {
    uint8_t enable, mode, speed;
    scanf("%hhu %hhu %hhu", &enable, &mode, &speed);

    uint16_t reg = build_register(enable, mode, speed);
    printf("%u", reg);

    return 0;
}

Solving Approach