int8_t *conv(uint32_t num, void *buff, int endianess)
{
    uint8_t *arr = buff;

    if(endianess)
        for(int i = 0; i < sizeof(num); i++)
        {
            arr[i] = num;
            num >>= 8;
        }
    else
        for(int i = sizeof(num) - 1; i >= 0; i--)
        {
            arr[i] = num;
            num >>= 8;
        }

    return buff;
}

https://godbolt.org/z/M7YqrW1j1

我假设你的“32位二进制”数据是一个有符号的32位整数。如果是这样的话，试试这个：

uint32_t some_number = <some 32 bit signed or unsigned int>;
int8_t data[4] = { 0 };
data[0] = (int8_t)(some_number>>24);
data[1] = (int8_t)(some_number>>16);
data[2] = (int8_t)(some_number>>8);
data[3] = (int8_t)(some_number);