main.cpp

An application used to vote, for example in the school, where a teacher have a lot of student and want to know their respons to a question. The teacher using a PC can see the answer of all student on his PC. every student have one of this box and they are connected through RS422 and the PC using a rs232/rs422 converter make a polling for each one of this box and can see the key pressed. (by Gianni Franchi).



#include "p16f84.h"

#include "serial.h"

#include "network.h"



#pragma CLOCK_FREQ 12000000



// Configuration Bits Oscillator=XP, all fuse OFF

asm __config H'3FF9'





// Function definition

void Init ();

char GetKey ();







// Address of this slave, change it for each slave



#define ADDRESS         1  





// this is a delay that every slave have to wait multiplied his address, so

// the slave 1 wait 5 ms, the slave 2 wait 10 ms and so on

// in this case the pc send a broadcast message, and every slave reply after a specified

// time, so the Master (PC) doesnt need to poll every slave, just send a message on the

// bus and who is on line just send a "alive" message

// this is usually called time slot network?? i dont remember if is the right name...



#define MAIN_TX_DELAY   5  





main()

{

   char Led_Verde=1; // Leds on my board GREEN

   char Led_Giallo=0;   // Leds on my board YELLOW

   char Led_Rosso=0; // Leds on my board RED

   int i;



   char Key;



   Init ();







   while (1)

   {

      // Turn Led on on Port A

      if (Led_Verde) porta|=4; else porta&=251;

      if (Led_Giallo) porta|=8; else porta&=247;

      if (Led_Rosso) porta&=239; else porta|=16;





      // Check if there is a packet sent from Master

      if (Net_Receive(0)==NET_OK)

      {

         // Time Slot...every slave wait a specified time to permit

         // the precedent slave to send the packet

         for (i=0;i<ADDRESS;i++) delay_ms (MAIN_TX_DELAY);



         // Turn on/Off the RED depending the command sent from master

         if (NetBuf[1]==1) Led_Rosso=1;

         if (NetBuf[1]==2) Led_Rosso=0;



         // Now fill the buffer that the slave send to master

         NetBuf[0]=ADDRESS;   // The slave address

         NetBuf[1]=GetKey();  // Get the status of the keybaord (a simply 12 keys)



         // Send the information to the master

         Net_Send (NetBuf[0],NetBuf[1]);



         // Turn on the Yellow led if a key is pressed

         if (NetBuf[1]) Led_Giallo=1; else Led_Giallo=0;

      }

   }

}





/*

   **********************

   System initialization

   **********************

*/

void Init ()

{

   option_reg = 6;   // set prescaler to 1:128

    trisa = 1;       // Set PA0 as input

    porta = 0;       // Clear porta

    trisb = 112;     // set PB0..PB3/PB7 as output PB4,PB5,PB6 as input

    portb = 15;





   MS_TIMER=0;



    enable_interrupt( GIE );  // Enable interrupt

    enable_interrupt( T0IE );  //enable TMR0 overflow bit



    Net_Init ();  // Packet initialization

}





// Keyboard mapping

const char Keys[]={'A','0','C','7','8','9','4','5','6','1','2','3'};





/*

   Getting the state of the keyboard

   this is done scanning each row of the keyboard

*/

char GetKey ()

{

   char Row=14;

   char Key=0;

   char App;

   int i;



   for (i=0;i<4;i++)

   {

      portb=Row;           // Se the line low and check what input pin is HIGH

      App=(portb & 0x70)>>4;

      switch (App)

      {

         case 6:

            Key=Keys[i*3];

         break;

         case 5:

            Key=Keys[i*3+1];

         break;

         case 3:

            Key=Keys[i*3+2];

         break;

      }

      Row=Row << 1;        // check the next row

      Row=Row | 1;

      Row=Row & 0x0F;

   }

   return Key;

}

http://www.sourceboost.com/home.html