LED sign control help for a Fireman

This is a discussion on LED sign control help for a Fireman within the C Programming forums, part of the General Programming Boards category; I have taken an alerting system and built it to use at my station. That being said my programming knowledge ...

  1. #1
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    LED sign control help for a Fireman

    I have taken an alerting system and built it to use at my station. That being said my programming knowledge is all self taught. Im hoping someone will be able to help me finish my last error or at least point me in the right direction.
    The code below is the control program for a LED signboard. The lines towards the bottom that read "n = write(fd,"\x61\x1C\x32",2);" control the colors for the board. Now to the problem, the board displays any color it wants it is not following what it is supposed to. Any one have any help to give.

    Code:
    #include <stdio.h>
    #include <string.h>
    #include <stdlib.h>
    #include <unistd.h>
    #include <fcntl.h>
    #include <errno.h>
    #include <termios.h>
    #include <sys/types.h>
    #include <sys/stat.h>
    
    #include "betabrite.h"
    
    #define DEFAULT_SERIAL_PORT "/dev/com1" /* Cygwin */
    
    int OpenPort(char *serial_port) {
    
       int fd ;
    
       fd = open(serial_port, O_RDWR|O_NOCTTY|O_NDELAY) ;
    
       if (fd == -1) {
          perror("OpenPort: Unable to open port - ") ;
       } else {
          fcntl(fd,F_SETFL,0) ;
       } /* if */
       
       return(fd) ;
    
    } /* OpenPort() */
    
    /* SetupSerial() - open the serial port and setup comm parameters */
    
    int SetupSerial(char *serial_port) {
    
       struct termios options ;
    
       int fd = OpenPort(serial_port) ;
    
       tcgetattr(fd,&options) ;
    
       /* 9600 baud */
    
       cfsetispeed(&options,B9600) ;
       cfsetospeed(&options,B9600) ;
    
       options.c_cflag |= (CLOCAL|CREAD) ;
    
       tcsetattr(fd,TCSANOW,&options) ;
    
       /* 7 bits */
    
       options.c_cflag &= ~CSIZE ;
       options.c_cflag |= CS7 ;
    
       /* even parity */
    
       options.c_cflag |= PARENB ;
       options.c_cflag &= ~PARODD ;
       options.c_cflag &= ~CSTOPB ;
       options.c_cflag &= ~CSIZE ;
       options.c_cflag |= CS7 ;
    
       /* software flow */
    
       options.c_iflag |= (IXON | IXOFF | IXANY) ;
    
       options.c_oflag &= ~OPOST;
       options.c_oflag &= ~ONLCR;
       options.c_oflag &= ~OCRNL;
    
       tcsetattr(fd,TCSANOW,&options);
    
       return(fd) ;
    
    } /* SetupSerial() */
    
    int main(int argc, char **argv) {
    	
    	int fd;
    	int n;
    	char *serial_port = DEFAULT_SERIAL_PORT;
    
    	fd = SetupSerial(serial_port) ;
    
    	n = write(fd,"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0",20) ;
    	n = write(fd,"\001Z00\002",5);
    
    	if(argv[1] == 'a' && argv[2] == 'a')
    		n = write(fd,"A0",2);
    	else {
    		n = write(fd,"A0\x1B ",3);
    
    		if(argv[2] == 'f')
    			n = write(fd,'c',1);
    		else
    			n = write(fd,'a',1);
    
    		if(argv[1] == 'g')
    			n = write(fd,"\x61\x1C\x32",2);
    		else if(argv[1] == 'r')
    			n = write(fd,"\x61\x1C\x31",2);
    		else 
    			n = write(fd,"\x61\x1C\x38",2);
    	
    		n = write(fd,argv[3],strlen(argv[3]));
    	}
    
    	//n = write(fd,"AA\x1B b",5);
    	//n = write(fd,"\x1C\x32\x08\x07A",3);
    
    	n = write(fd,"\004",1);
    	close(fd);
    
    	return(0);
    }

  2. #2
    Guest Sebastiani's Avatar
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    //if(argv[1] == 'a' && argv[2] == 'a')

    You're can't compare an array of char with a character in C! Use strcmp, eg:

    Code:
    if(strcmp(argv[1], "a") == 0 && strcmp(argv[2], "a") == 0)
    Also, it might be a good idea to check that argc == 3, and if not, print a 'usage' message...
    Code:
    #include <cmath>
    #include <complex>
    bool euler_flip(bool value)
    {
        return std::pow
        (
            std::complex<float>(std::exp(1.0)), 
            std::complex<float>(0, 1) 
            * std::complex<float>(std::atan(1.0)
            *(1 << (value + 2)))
        ).real() < 0;
    }

  3. #3
    and the hat of wrongness Salem's Avatar
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    > n = write(fd,"\x61\x1C\x38",2);
    Perhaps because the string you're trying to send is 3 chars, and you only send two.

    With the exception of the first set of nul's, something like this would be a lot less error prone.
    Code:
    int myWriteString ( int fd, const char *msg ) {
      return write( fd, msg, strlen(msg);
    }
    So you can do
    n = myWriteString( fd, "\x61\x1C\x38" );
    without having to do manual edits of the length every time you change the string.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  4. #4
    Registered User
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    Nov 2008
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    Salem Im not exactly sure where this line of code is supposed to go. Please forgive me Im still learning all this as I go.

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