45. Serialized Data Buffer

#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];
    buffer[0]=0xA5;
    buffer[1]=command;
    buffer[2]=value;
    buffer[3]=(value>>8);
    buffer[4]=status;
    buffer[5]=(checksum&0xFF);
    buffer[6]=(checksum&(0xFF<<8))>>8;
    buffer[7]=(checksum&(0xFF<<16))>>16;
    buffer[8]=(checksum&(0xFF<<24))>>24;
    buffer[9]=0x5A;
    for(int i=0; i<=9;i++){
        printf("%d ", buffer[i]);
    }

   /*
    uint32_t tot=0x00;
    tot |= ((0xA5) | (command<<8) | (value<<16) | (status<<32) | (checksum<<40) | (0x5A<<72));
    
    for(int i=0; i<=9; i++){
        //printf("%d ", ((tot&(0xFF<<8*i)))>>8*i);
        //printf("%d ", (tot&0xFF));
        printf("%d ", tot);
        tot=tot>>8;
    }
    */
    // 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;
}

The MSB bits are truncated if you assigns a 16 bit word to a 8bit value

Refer buffer[2]