//-----------------------------------------------------------------------------
// F500_UART0_Interrupt.c
//-----------------------------------------------------------------------------
// Copyright 2008 Silicon Laboratories, Inc.
// http://www.silabs.com
//
// Program Description:
//
// This program demonstrates how to configure the C8051F500 to write to and 
// read from the UART interface. The program reads a word using the UART 
// interrupts and outputs that word to the screen, with all characters in 
// uppercase.
//
// How To Test:
//
// 1) Ensure that jumpers are placed on J17 of the C8051F500 target board
//    that connect the P0.4 pin to the TX signal, and P0.5 to the RX signal
// 2) Connect USB cable from the development board to a PC
// 3) Specify the target baudrate in the constant <BAUDRATE>
// 4) On the PC, open HyperTerminal (or any other terminal program) and connect
//    to the USB port (virtual com port) at <BAUDRATE>, 8 data bits, no parity,
//    1 stop bit and no flow control
// 5) Download and execute code on an 'F500 target board
// 6) Type up to 64 characters into the Terminal and press Enter. The MCU
//    will then print back the characters that were typed
//
// Target:         C8051F500 (Side A of a C8051F500-TB)
// Tool chain:     Keil C51 8.0 / Keil EVAL C51
// Command Line:   None
//
// Release 1.0 / 10 MAR 2008 (GP)
//    -Initial Revision
//

//-----------------------------------------------------------------------------
// Includes
//-----------------------------------------------------------------------------

#include <compiler_defs.h>
#include <C8051F500_defs.h>            // SFR declarations
#include <stdio.h>

//-----------------------------------------------------------------------------
// Global CONSTANTS
//-----------------------------------------------------------------------------

#define SYSCLK           24000000      // SYSCLK frequency in Hz
#define BAUDRATE           115200      // Baud rate of UART in bps

//-----------------------------------------------------------------------------
// Function PROTOTYPES
//-----------------------------------------------------------------------------

void SYSCLK_Init (void);
void UART0_Init (void);
void PORT_Init (void);

INTERRUPT_PROTO (UART0_ISR, INTERRUPT_UART0);

//-----------------------------------------------------------------------------
// Global Variables
//-----------------------------------------------------------------------------

#define UART_BUFFERSIZE 64
U8 UART_Buffer[UART_BUFFERSIZE];
U8 UART_Buffer_Size = 0;
U8 UART_Input_First = 0;
U8 UART_Output_First = 0;
U8 TX_Ready = 1;
static U8 Byte;

//-----------------------------------------------------------------------------
// MAIN Routine
//-----------------------------------------------------------------------------

void main (void)
{
   SFRPAGE = ACTIVE_PAGE;              // Change for PCA0MD

   PCA0MD &= ~0x40;                    // Disable watchdog timer

   PORT_Init ();                       // Initialize Port I/O
   SYSCLK_Init ();                     // Initialize Oscillator
   UART0_Init ();                      // Initialize UART

   EA = 1;                             // Enable global interrutpts

   while (1)
   {
      // If the complete word has been entered via the terminal followed by
      // carriage return

      if((TX_Ready == 1) && (UART_Buffer_Size != 0) && (Byte == 13))
      {
         TX_Ready = 0;                 // Set the flag to zero
         TI0 = 1;                      // Set transmit flag to 1
      }
   }
}

//-----------------------------------------------------------------------------
// Initialization Subroutines
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
// PORT_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// Configure the Crossbar and GPIO ports.
//
// P0.4   digital   push-pull    UART TX
// P0.5   digital   open-drain   UART RX
//
//-----------------------------------------------------------------------------
void PORT_Init (void)
{
   U8 SFRPAGE_save = SFRPAGE;
   SFRPAGE = CONFIG_PAGE; 

   P0MDOUT |= 0x10;                    // Enable UTX as push-pull output
   XBR0    = 0x01;                     // Enable UART on P0.4(TX) and P0.5(RX)
   XBR2    = 0x40;                     // Enable crossbar and weak pull-ups

   SFRPAGE = SFRPAGE_save;
}

//-----------------------------------------------------------------------------
// SYSCLK_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// This routine initializes the system clock to use the internal oscillator
// at its maximum frequency.
// Also enables the Missing Clock Detector.
//-----------------------------------------------------------------------------

void SYSCLK_Init (void)
{
   U8 SFRPAGE_save = SFRPAGE;
   SFRPAGE = CONFIG_PAGE; 

   OSCICN |= 0x87;                     // Configure internal oscillator for
                                       // its maximum frequency
   RSTSRC  = 0x04;                     // Enable missing clock detector

   SFRPAGE = SFRPAGE_save;
}

//-----------------------------------------------------------------------------
// UART0_Init
//-----------------------------------------------------------------------------
//
// Return Value : None
// Parameters   : None
//
// Configure the UART0 using Timer1, for <BAUDRATE> and 8-N-1.
//-----------------------------------------------------------------------------
void UART0_Init (void)
{
   U8 SFRPAGE_save = SFRPAGE;
   SFRPAGE = CONFIG_PAGE; 

   SCON0 = 0x10;                       // SCON0: 8-bit variable bit rate
                                       // clear RI0 and TI0 bits

 // Baud Rate = [BRG Clock / (65536 - (SBRLH0:SBRLL0))] x 1/2 x 1/Prescaler

#if   ((SYSCLK / BAUDRATE / 2 / 0xFFFF) < 1)
      SBRL0 = -(SYSCLK / BAUDRATE / 2);
      SBCON0 |= 0x03;                  // Set prescaler to 1
#elif ((SYSCLK / BAUDRATE / 2 / 0xFFFF) < 4)
      SBRL0 = -(SYSCLK / BAUDRATE / 2/ 4);
      SBCON0 &= ~0x03;
      SBCON0 |= 0x01;                  // Set prescaler to 4
#elif ((SYSCLK / BAUDRATE / 2 / 0xFFFF) < 12)
      SBRL0 = -(SYSCLK / BAUDRATE / 2 / 12);
      SBCON0 &= ~0x03;                 // Set prescaler to 12
#else
      SBRL0 = -(SYSCLK / BAUDRATE / 2 / 48);
      SBCON0 &= ~0x03;
      SBCON0 |= 0x02;                  // Set prescaler to 48
#endif

   SBCON0 |= 0x40;                     // Enable baud rate generator
   ES0 = 1;                            // Enable UART0 interrupts

   TX_Ready = 1;                       // Flag showing that UART can transmit

   SFRPAGE = SFRPAGE_save;
}

//-----------------------------------------------------------------------------
// Interrupt Service Routines
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
// UART0_Interrupt
//-----------------------------------------------------------------------------
//
// This routine is invoked whenever a character is entered or displayed on the
// Hyperterminal.
//
//-----------------------------------------------------------------------------

INTERRUPT(UART0_ISR, INTERRUPT_UART0)
{
   if (RI0 == 1)
   {
      if( UART_Buffer_Size == 0)       // If new word is entered
      {
         UART_Input_First = 0;    
      }

      RI0 = 0;                         // Clear interrupt flag

      Byte = SBUF0;                    // Read a character from UART

      if (UART_Buffer_Size < UART_BUFFERSIZE)
      {
         UART_Buffer[UART_Input_First] = Byte; // Store in array

         UART_Buffer_Size++;           // Update array's size

         UART_Input_First++;           // Update counter
      }
   }

   if (TI0 == 1)                       // Check if transmit flag is set
   {
      TI0 = 0;                         // Clear interrupt flag

      if (UART_Buffer_Size != 1)       // If buffer not empty
      {
         // If a new word is being output
         if (UART_Buffer_Size == UART_Input_First) 
         {
              UART_Output_First = 0;  
         }

         // Store a character in the variable byte
         Byte = UART_Buffer[UART_Output_First];

         if ((Byte >= 0x61) && (Byte <= 0x7A))  // If upper case letter
         { 
            Byte -= 32; 
         }

         SBUF0 = Byte;                 // Transmit to Hyperterminal

         UART_Output_First++;          // Update counter

         UART_Buffer_Size--;           // Decrease array size

      }
      else
      {
         UART_Buffer_Size = 0;         // Set the array size to 0
         TX_Ready = 1;                 // Indicate transmission complete
      }
   }
}

//-----------------------------------------------------------------------------
// End Of File
//-----------------------------------------------------------------------------