Raspberry Pie: the serial port has been unable to read the information sent by the upper computer

Raspberry pie serial port has been unable to read the information sent by the upper computer

Error message ：

No error message …( What programmers fear most is that they don't report errors BUG Is that right ).

however , Strangely enough , After entering the value from the keyboard , Enter again , Something magical has happened .....

Raspberry pie takes the value I input from the keyboard as a serial command ！！

reason

When writing the startup serial port code , You can't write that

Control_Voice.c Under the document

// Error code ：
int init_Voice(struct Command *cmd ,char *ip,char *port){
    
        int fd;
        if(fd = serialOpen("/dev/ttyAMA0",9600) == -1){
    		/* After debugging , In this way if In the sentence , Assign to fd The value of is 0, yes 0 ah ！ Guys ！！！ Although the document says, it's not -1, The normal value is returned ,（ I believe you're a ghost ！！！） But there are problems here ~~~~*/
                exit(-1);
        }
        cmd->fd = fd;
        return fd;
}

correct

int fd;
fd = serialOpen("/dev/ttyAMA0",9600);	// Purple sauce is OK 
if(fd == -1){
    
	exit(-1);
}
cmd->fd = fd;
return fd;

4、

    if(fd = serialOpen("/dev/ttyAMA0",9600) == -1){
    		/* After debugging , In this way if In the sentence , Assign to fd The value of is 0, yes 0 ah ！ Guys ！！！  Although the document says, it's not -1, The normal value is returned ,（ I believe you're a ghost ！！！）  But there are problems here ~~~~*/
                exit(-1);
        }
        cmd->fd = fd;
        return fd;
}

correct

int fd;
fd = serialOpen("/dev/ttyAMA0",9600);	// Purple sauce is OK 
if(fd == -1){
    
	exit(-1);
}
cmd->fd = fd;
return fd;