Macro-Based Register Config Helper

Use bitwise in macros.

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

// Define macros here
#define en(reg, e)     (reg |= (e & 1U) << 0 )
#define mode(reg, m)   (reg |= (m & 3U) << 1)
#define spd(reg, s)    (reg |= (s & 7U) << 3)

uint16_t build_register(uint8_t enable, uint8_t mode, uint8_t speed) {
    uint16_t reg = 0;
    en(reg, enable);
    mode(reg, mode);
    spd(reg, speed);
    return reg;
}

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

• Each macro masks value to field width
• Shifts it to correct bit position
• OR’d into the register