// transmitter.c
// Runs on LM3S1968
// Used to test the transmitter.c driver
// 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"

#define Ready (*((volatile unsigned long *)0x40026004))  // PG0
#define Ack   (*((volatile unsigned long *)0x40026008))  // PG1
#define Data  (*((volatile unsigned long *)0x400253FC))  // Port F
// Initialize transmitter
void Xmt_Init(void){  volatile unsigned long delay;
  SYSCTL_RCGC2_R |= 0x00000060; // activate Ports F and G
  delay = SYSCTL_RCGC2_R;    // allow time to finish activating
  Ready = 0;                
  GPIO_PORTG_DIR_R |= 0x01;  // PG0 is Ready out
  GPIO_PORTG_DIR_R &= ~0x02; // PG1 is Ack in
  GPIO_PORTG_DEN_R |= 0x03;  // enable digital I/O on PG1-0
  GPIO_PORTF_DIR_R = 0xFF;   // make PF7-0 out data
  GPIO_PORTF_DEN_R = 0xFF;   // enable digital I/O on PF7-0
}
// Transmitter
// Handshaked
void Xmt_Out(unsigned char data){ 
  Data = data;       // 1)
  Ready = 1;         // 2)
  while(Ack){};      // 3)
  while(Ack == 0){}; // 5)
  Ready = 0;         // 6)
}