【原创】TIVA 关于SysCtlDelay()准确延时的测试

    UARTprintf("Hello, world!\n");

    ui32Loop=0;

    ui32Loop=ROM_SysCtlClockGet();

    UARTprintf("%d\n",ui32Loop);

    ui32Loop=0;

    ui32Loop=SysCtlClockGet();

    UARTprintf("%d\n",ui32Loop);

//*****************************************************************************

//

// hello.c - Simple hello world example.

//

// Copyright (c) 2012-2014 Texas Instruments Incorporated.  All rights reserved.

// Software License Agreement

//

// Texas Instruments (TI) is supplying this software for use solely and

// exclusively on TI's microcontroller products. The software is owned by

// TI and/or its suppliers, and is protected under applicable copyright

// laws. You may not combine this software with "viral" open-source

// software in order to form a larger program.

//

// THIS SOFTWARE IS PROVIDED "AS IS" AND WITH ALL FAULTS.

// 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. TI SHALL NOT, UNDER ANY

// CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL, OR CONSEQUENTIAL

// DAMAGES, FOR ANY REASON WHATSOEVER.

//

// This is part of revision 2.1.0.12573 of the EK-TM4C123GXL Firmware Package.

//

//*****************************************************************************



#include <stdint.h>

#include <stdbool.h>

#include "inc/hw_memmap.h"

#include "inc/hw_types.h"

#include "driverlib/debug.h"

#include "driverlib/fpu.h"

#include "driverlib/gpio.h"

#include "driverlib/pin_map.h"

#include "driverlib/rom.h"

#include "driverlib/sysctl.h"

#include "driverlib/uart.h"

//#include "utils/uartstdio.h"



//*****************************************************************************

//

//! \addtogroup example_list

//! <h1>Hello World (hello)</h1>

//!

//! A very simple ``hello world'' example.  It simply displays ``Hello World!''

//! on the UART and is a starting point for more complicated applications.

//!

//! UART0, connected to the Virtual Serial Port and running at

//! 115,200, 8-N-1, is used to display messages from this application.

//

//*****************************************************************************



//*****************************************************************************

//

// The error routine that is called if the driver library encounters an error.

//

//*****************************************************************************

#ifdef DEBUG

void

__error__(char *pcFilename, uint32_t ui32Line)

{

}

#endif



////*****************************************************************************

////

//// Configure the UART and its pins.  This must be called before UARTprintf().

////

////*****************************************************************************

//void

ConfigureUART(void)

{

//    //

//    // Enable the GPIO Peripheral used by the UART.

//    //

    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);



//    //

//    // Enable UART0

//    //

    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_UART0);



//    //

//    // Configure GPIO Pins for UART mode.

//    //

    ROM_GPIOPinConfigure(GPIO_PA0_U0RX);

   ROM_GPIOPinConfigure(GPIO_PA1_U0TX);

    ROM_GPIOPinTypeUART(GPIO_PORTA_BASE, GPIO_PIN_0 | GPIO_PIN_1);



//    //

//    // Use the internal 16MHz oscillator as the UART clock source.

//    //

    UARTClockSourceSet(UART0_BASE, UART_CLOCK_PIOSC);



//    //

//    // Initialize the UART for console I/O.

//    //

    UARTStdioConfig(0, 115200, 16000000);

}



//*****************************************************************************

//

// Print "Hello World!" to the UART on the evaluation board.

//

//*****************************************************************************

int

main(void)

{

    volatile uint32_t ui32Loop;



    //

    // Enable lazy stacking for interrupt handlers.  This allows floating-point

    // instructions to be used within interrupt handlers, but at the expense of

    // extra stack usage.

    //

  //  ROM_FPULazyStackingEnable();



    //

    // Set the clocking to run directly from the crystal.

    //

    ROM_SysCtlClockSet(SYSCTL_SYSDIV_4 | SYSCTL_USE_PLL | SYSCTL_XTAL_16MHZ |

                       SYSCTL_OSC_MAIN);



    //

    // Enable the GPIO port that is used for the on-board LED.

    //

    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);



    //

    // Enable the GPIO pins for the LED (PF2 & PF3).

    //

    ROM_GPIOPinTypeGPIOOutput(GPIO_PORTF_BASE, GPIO_PIN_2);



    //

    // Initialize the UART.

    //

    ConfigureUART();



//    //

//    // Hello!

//    //

    UARTprintf("Hello, world!\n");

    ui32Loop=0;

    ui32Loop=ROM_SysCtlClockGet();

    UARTprintf("%d\n",ui32Loop);

    ui32Loop=0;

    ui32Loop=SysCtlClockGet();

    UARTprintf("%d\n",ui32Loop);

    //

    // We are finished.  Hang around doing nothing.

    //

    while(1)

    {

        //

        // Turn on the BLUE LED.



/*        GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_2, GPIO_PIN_2);



        //

        // Delay for a bit.

        //

        SysCtlDelay(50000000 / 3000);



        //

        // Turn off the BLUE LED.

        //

        GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_2, 0);



        //

        // Delay for a bit.

        //

        SysCtlDelay(50000000 / 3000);*/

                    GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_2, GPIO_PIN_2);



                    //

                    // Delay for a bit.

                    //

                    SysCtlDelay(ROM_SysCtlClockGet() / 3000);



                    //

                    // Turn off the BLUE LED.

                    //

                    GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_2, 0);



                    //

                    // Delay for a bit.

                    //

                    SysCtlDelay(ROM_SysCtlClockGet() / 3000);

    }

}