/* p6_5.c: Modified p4_2.c to use interrupt driven. */

/* Read data from UART0 and display it at the tri-color LEDs. The LEDs are connected to Port F 3-1. Press any A-z, a-z, 0-9 key at the terminal emulator and see ASCII value in binary is displayed on LEDs of PORTF. */

/* notice in Table 6-7, IRQ5 is assigned to UART0 */

#include "tm4c123gh6pm.h"

int main(void) 
{
    SYSCTL->RCGCUART |= 1;  /* provide clock to UART0 */
    SYSCTL->RCGCGPIO |= 1;  /* enable clock to PORTA */
    SYSCTL->RCGCGPIO |= 0x20; /* enable clock to PORTF */
    
    /* UART0 initialization */
    UART0->CTL = 0;         /* disable UART0 */
    UART0->IBRD = 104;      /* 16MHz/16=1MHz, 1MHz/104=9600 baud rate */
    UART0->FBRD = 11;       /* fraction part, see Example 4-4 */
    UART0->CC = 0;          /* use system clock */
    UART0->LCRH = 0x60;     /* 8-bit, no parity, 1-stop bit, no FIFO */
    UART0->IM |= 0x0010;    /* enable RX interrupt */
    UART0->CTL = 0x301;     /* enable UART0, TXE, RXE */

    /* UART0 TX0 and RX0 use PA0 and PA1. Set them up. */
    GPIOA->DEN = 0x03;      /* Make PA0 and PA1 as digital */
    GPIOA->AFSEL = 0x03;    /* Use PA0,PA1 alternate function */
    GPIOA->PCTL = 0x11;     /* configure PA0 and PA1 for UART */
    
    GPIOF->DIR = 0x0E;      /* configure Port F to control the LEDs */
    GPIOF->DEN = 0x0E;
    GPIOF->DATA = 0;

    /* enable interrupt in NVIC and set priority to 6 */
    NVIC->IP[5] = 3 << 5;   /* set interrupt priority to 3 */
    NVIC->ISER[0] |= 0x00000020;  /* enable IRQ5 for UART0 */

    __enable_irq(); /* global enable IRQs */

    for(;;)
    {
    }
}

void UART0_Handler(void)
{
    volatile int readback;

    char c;
    if (UART0->MIS & 0x0010)
    {
        c = UART0->DR;              /* read the received data */
        GPIOF->DATA = c << 1;       /* shift left and write it to LEDs */
        UART0->ICR = 0x0010;        /* clear Rx interrupt flag */
        readback = UART0->ICR;      /* a read to force clearing of interrupt flag */
    }
    else
    {
        /* should not get here. But if it does, */
        UART0->ICR = UART0->MIS;    /* clear all interrupt flags */
        readback = UART0->ICR;      /* a read to force clearing of interrupt flag */
    }
}

/* This function is called by the startup assembly code to perform system specific initialization tasks. */
void SystemInit(void)
{
    __disable_irq();    /* disable all IRQs */
    
    /* Grant coprocessor access */
    /* This is required since TM4C123G has a floating point coprocessor */
    SCB->CPACR |= 0x00F00000;
}