// receiver.c
// Runs on LM3S1968
// Valvano
// August 5, 2011

/* This example accompanies the book
   "Embedded Systems: Real Time Interfacing to the Arm Cortex M3",
   ISBN: 978-1463590154, Jonathan Valvano, copyright (c) 2011
   
   Example 4.4, Section 4.8, Programs 4.9, 4.10 and 4.11
   Circuit Figure 4.34

 Copyright 2011 by Jonathan W. Valvano, valvano@mail.utexas.edu
    You may use, edit, run or distribute this file
    as long as the above copyright notice remains
 THIS SOFTWARE IS PROVIDED "AS IS".  NO WARRANTIES, WHETHER EXPRESS, IMPLIED
 OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, IMPLIED WARRANTIES OF
 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE.
 VALVANO SHALL NOT, IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL,
 OR CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER.
 For more information about my classes, my research, and my books, see
 http://users.ece.utexas.edu/~valvano/
 */
 
// Transmitter PG0 output Ready to receiver PG1 input
// Receiver PG0 output Ack to transmitter PG1 input
// Transmitter Port F output to receiver Port F input

#include "lm3s1968.h"


// Initialize receiver
#define Ack   (*((volatile unsigned long *)0x40026004))   // PG0
#define Ready (*((volatile unsigned long *)0x40026008))   // PG1
#define Data  (*((volatile unsigned long *)0x400253FC))   // Port F
void Rcv_Init(void){  volatile unsigned long delay;
  SYSCTL_RCGC2_R |= 0x00000060; // activate Ports F and G
  delay = SYSCTL_RCGC2_R;    // allow time to finish activating
  GPIO_PORTG_DIR_R |= 0x01;  // PG0 is Ack out
  GPIO_PORTG_DIR_R &= ~0x02; // PG1 is Ready in
  GPIO_PORTG_DEN_R |= 0x03;  // enable digital I/O on PG1-0
  GPIO_PORTF_DIR_R = 0x00;   // make PF7-0 input data
  GPIO_PORTF_DEN_R = 0xFF;   // enable digital I/O on PF7-0
  Ack = 1;          
}

// Receiver
// Handshaked
// Receiver
unsigned char Rcv_In(void){ 
unsigned char data;
  while(Ready == 0){}; // 2)
  Ack = 0;              // 3)
  data = Data;          // 4) 
  Ack = 1;              // 5)
  while(Ready){};       // 6)
  return(data);
}