Creating a program and library to the MSP

In this post we will talk about the libraries already used in the previous example and create new libraries from the analysis of the example.
Let's start with the libraries already used, they are: msp430.h , msp430f2013.h, in430.h e intrinsics.h.

These are basic libraries that determine since which MSP microcontroller family is being used, even set some functions used to control the board:

• "msp430.h": this library has only the function to call the “.h” responsible for each version of msp.
• "msp430f2013.h": this is the file that is called to the MSP we are using
• is responsible for basic configurations and settings to control the board, such as doors, inputs and outputs, watchdog, registers, timers, bit settings, memory, interrupt.
• "in430.h": Sets the intrinsic functions and mapping compiler for the MSP430 IAR Systems C / C + +.
• "intrinsics.h": registration code intrinsic of functions of IAR Embedded Workbench for MSP430.

To show how to create libraries we decided to start the analysis from the example of the LED, and modify it to a Morse code.
But before that, a quick and (perhaps) is instructive summary of what the morse code:
Morse code is a system of representing letters, numbers and punctuation marks through a coded signal sent intermittently.

It was developed by Samuel Morse in 1835, creator of the electric telegraph, a device that uses electrical currents to control electromagnets that work for emission or reception of signals.
A coded message in Morse can be transmitted in various ways in pulses (or tones) short and long:

• electrical pulses transmitted through a cable;
• mechanical waves (noise disturbance);
• visual signals (lights turning on and off, as our LED);
• electromagnetic waves (radio signals);

This system represents letters, numbers and punctuation marks with just a sequence of dots, dashes, and spaces.
Probably the most famous Morse code in the word is the SOS, one of the most used and signals sent in emergency situations.

In popular usage, SOS was associated with phrases such as "Save Our Seamen”, "Save Our Ship”, "Survivors On Shore" or "Save Our souls ". These phrases, however, appeared later, as a way to help remember the letters correctly (a retro-acronym). As a code, the letters SOS do not have a meaning for themselves.

Now back to embedded programming, let's consider a program that can transmit the message with just the led.
Analyzing the code of the flashing LED realize that the command responsible for turning on and off the LED is "P1OUT ^ = 0x01;", and that it must be declared as output "P1DIR | = 0x01;."
From these two commands, and a Morse code table decided to create a library that allows easily for the programmer to send a coded message in Morse code through the LED.
Use a program of your choice to build and save the following code as libraries. The following code corresponding to the library foundation for the program:

#include "CodigoMorse.h"

#include "msp430.h"

#define T_LONGO 30000   //the longer time will be used for the representation of character traits ans between characters

#define T_CURTO 10000   //the shortest time will be used for the representation of points and beyween signals

unsigned int i;

//definitions of times and outputs

void TempoCurto(void)  //TempoCurto means short time

{

      for (i=0;i<T_CURTO;i++);

}

void TempoLongo(void)   //TempoLongo means long time

{

      for (i=0;i<T_LONGO;i++);

}

void TempoEntreSinais (void)  //TempoEntreSinais means time between signals

{

      for (i=0;i<T_CURTO;i++);

}

void TempoEntreLetras (void)  //TempoEntreLetras means time between letters

{

      for (i=0;i<T_LONGO;i++);

}

void CodigoMorseTraco (void)   //TempoEntreLetras morse code traice

{

      P1OUT |= 0x01;   //turn on led

      TempoLongo();

      P1OUT &= ~0x01;  //turn off led

      TempoEntreSinais();

}

void CodigoMorsePonto (void)  //TempoEntreLetras morse code dot

{

      P1OUT |= 0x01;      // turn on led

      TempoCurto();

      P1OUT &= ~0x01;   // turn off led

      TempoEntreSinais();

}

//character sets

void CodigoMorseO (void)

{

      CodigoMorseTraco();

      CodigoMorseTraco();

      CodigoMorseTraco();

      TempoEntreLetras();

}

void CodigoMorseS (void)

{

      CodigoMorsePonto();

      CodigoMorsePonto();

      CodigoMorsePonto();

      TempoEntreLetras();

}

//character selection

void CodigoMorse (char caracter)

{

//teste to see if the character that is coming I possible to represent in Morse Code

      if  

  (

     (caracter == 33) ||

     (caracter == 44) ||

     (caracter == 46) ||

     (caracter >= 48 && caracter <= 58) ||

     (caracter == 63) ||

     (caracter >= 65 && caracter <= 90) ||

     (caracter >= 97 && caracter <= 122)

      )

  {

           case 'O':

           case 'o':

           CodigoMorseO();

           break;

           case 'S':

           case 's':

           CodigoMorseS();

           break;

  }

}

Save with the name "CodigoMorse.c." The code only shows how to represent the letters O and S in Morse.
Create another document with the code of library functions:

#ifndef CodigoMorse_H

   #define CODIGOMORSE_H    //This function taks a character encoded in ASCII in the interval of 33 to 122

   void TempoCurto (void);

   void TempoLongo (void);

   void TempoEntreSinais (void);

   void TempoEntreLetras (void);

   void CodigoMorse (char caracter);

#endif

Save this file named "CodigoMorse.h." Notice that the header file only shows the functions of time (in case anyone wanted to do something beyond the standard strings) and a function that takes a character and automatically encodes it in Morse and presents it in the led.
This library will be used as follows:

for (;;) // Start infinite loop

{

      CodigoMorse('S');

      CodigoMorse('O');

      CodigoMorse('S');

      P1OUT = 0x00;      //Ends the message and waits before restarting

      for(i=0;i<10;i++)

      {

            TempoEntreLetras();   //spending time between messages

      }

}

With this, we have everything we need for next week send an SOS through the LED, we know that no one would see our SOS, but it is the basis for those who want to implement the idea to a larger scale.

In the next post we'll show you how to use libraries and how to build and debug the program in the Workbench.

See ya!