Serialized Data Buffer

Use pointer arithmetic and casting to pointers.

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

void build_packet(uint8_t command, uint16_t value, uint8_t status, uint32_t checksum) {
    uint8_t buffer[10];
    uint8_t i;
    *(buffer + 0) = 0xa5;
    *(buffer + 1) = command;
    *(uint16_t*)(buffer + 2) = value ;
    // *(buffer + 3) = (value >> 8) & 0xff;
    *(buffer + 4) = status;

    *(uint32_t*)(buffer + 5) = checksum ;
    // *(buffer + 6) = (checksum >> 8) & 0xff;
    // *(buffer + 7) = (checksum >> 8*2) & 0xff;
    // *(buffer + 8) = (checksum >> 8*3) & 0xff;
    
    *(buffer + 9) = 0x5a;
    
    for(i = 0; i<10; i++){
        printf("%d", buffer[i]);
        if(i < 10-1) putchar(' ');
    }
    // Your logic to fill buffer
    // Then print buffer
}

int main() {
    uint8_t cmd, status;
    uint16_t val;
    uint32_t crc;

    scanf("%hhu %hu %hhu %u", &cmd, &val, &status, &crc);
    build_packet(cmd, val, status, crc);
    return 0;
}

Solving Approach