[参考译文] EK-TM4C123GXL：使用串行通信协议 UART 通过端口 D 引脚 PD6和 PD7时出现问题

// ***** 1. Pre-processor Directives Section *****
#include <stdio.h>   // standard C library 


//This program prompts the user to enter a g (green), b (blue), or r (red) in the command UART window and responds by turning on the approporiate LED. 
//If an entry is wrong the user is prompted again.

#define RCGCUART_UART_CLOCKING (*((volatile unsigned long *)0x400FE618))//Writing to this register to control the clocking of the UART modules (PORTD)(PG.344)
#define GPIOAMSEL_GPIO_ANALOG_ENABLE_DISABLE (*((volatile unsigned long *)0x40007528))//Disabling the analog function (PG.687)
#define RCGC2_GPIO_CLOCK (*((volatile unsigned long *)0x400FE108)) //Clock enable for legacy software (PG.464) Legacy register.
#define RCGCGPIO_CLOCK_ENABLE (*((volatile unsigned long *)0x400FE608))//Enabling the clock to PORTD by writing to this register (PG.340)
#define GPIOAFSEL_ALTFUNCTION_CONTROL (*((volatile unsigned long *)0x4007420))//Setting the pins in this register to allow pins in PORTD to be controlled by an alt function (PG.671_
#define GPIOPCTL_ALTFUNCTION_SELECT (*((volatile unsigned long *)0x4000752C))//Selecting which pins your applying the alt function to(PG.688)
#define GPIODEN_DIGITAL_PIN_ENABLE (*((volatile unsigned long *)0x4000751C))//Enabling PORTD pins as digital I/O (PG.682)
#define UARTCTL_UART_ENABLE_DISABLE (*((volatile unsigned long *)0x4000E030))//Disabling the UART to setup the baud rate, serial parameters, and UART2 clock source (PG.918)
#define UARTIBRD_UART_BAUDRATE_INTEGER (*((volatile unsigned long *)0x4000E024))//Writing the appropriate value for the integer part of the baud rate UART2 (PG.914)
#define UARTFBRD_UART_BAUDRATE_FRACTIONAL (*((volatile unsigned long *)0x4000E028))//Writing the appropriate value for the fractional part of the baud rate for UART2 (PG.915)
#define UARTLCRH_SERIAL_PARAMETERS (*((volatile unsigned long *)0x4000E02C))//Setting up the serial parameter (data length, parity pits, stop bits, etc.) for UART2 (PG.916)
#define UARTCC_UART_CLOCK_SOURCE (*((volatile unsigned long *)0x4000EFC8))//Configuring the UART2 clock source (PG.939)

//The next define statements are for the LED_Config() function
#define RCGC2_GPIO_PORTF  (*((volatile unsigned long *)0x400FE108)) //PORTF clock enable (PG.464)
#define GPIODIR_DIR_PORTF 	(*((volatile unsigned long *)0x40025400)) //Setting the bits in this register configures a GPIO pin to be an output, clearing configures it to be an input(PG.663)
#define GPIODEN_DIGITAL_ENABLE_PORTF (*((volatile unsigned long *)0x4002551C)) //Setting the pins here enables their digital functions......clearing them disables the digital functions (PG.682)
#define GPIO_PORTF_DATA	(*((volatile unsigned long *)0x400253FC)) //Memory location of PORTF that you can write to to turn off/on LED's?
	
//The next define statements are for the read functions accepting user input
#define UARTFR_Flag_Register (*((volatile unsigned long *)0x4000E018)) //The flag register saying that FIFO is receiving/transferring data for UART2 (PG.911)
#define UARTDR_FIFO_DATA_REGISTER (*((volatile unsigned long *)0x4000E000)) //This is the data register aka the interface to the FIFO's. This is were data is written to when using FIFO(PG.906
#define GPIOLOCK_LOCK_REGISTER (*((volatile unsigned long *)0x40007520)) //GPIO lock register
#define GPIOCR_COMMIT_REGISTER (*((volatile unsigned long *)0x40007524)) //GPIO Commit register 
	
// ***** Subroutines Section *****
void Uart_Init(void);
void LED_Config (void);
char readChar (void);
void printChar (char c);
void printString (char *string);


int main (void) 
{
	char c;
	//Calling the UART initialization function
	Uart_Init();
	//Calling the LED configuration function
	LED_Config();
	//printString("Enter \"r\",\"g\",or\"b\":\n\r");
	printString("Enter \"r\",\"g\",\"w\",\"s\",or\"b\":\n\r");
	while(1)
	{
		printString("Enter \"r\",\"g\",\"w\",\"s\",or\"b\":\n\r");
		c = readChar();
		printChar(c);
		printString("\n\r");
		switch(c)
		{
			case 'r':
				GPIO_PORTF_DATA = (1<<1); //Turns on the red LED
			break;
			
			case 'b':
				GPIO_PORTF_DATA = (1<<2); //Turns on the blue LED
			break;
			
			case 'g':
				GPIO_PORTF_DATA = (1<<3);//Turns on the green LED
			break;
			
			case 'w':
				GPIO_PORTF_DATA = 0x0E;//Turns on the white LED
			break;
			
			case 's':
				GPIO_PORTF_DATA = 0x0C;//Turns on the sky blue LED
			break;
			
			
			default:
				GPIO_PORTF_DATA &= ~((1<<1) | (1<<2) | (1<<3)); 
			}
		}
}



void Uart_Init(void)
{
 
GPIOLOCK_LOCK_REGISTER  = 0x4C4F434B;
GPIOCR_COMMIT_REGISTER  = 11111111;
	//Enabling and providing a clock to UART module 2 in run mode.
	RCGCUART_UART_CLOCKING |= 0x04;
	//Enabling and providing a clock to GPIO PORTD in run mode.
	//RCGC2_GPIO_CLOCK |= (1<<3); 
	//Enabling and providing a clock to GPIO PORTD in run mode.
	RCGCGPIO_CLOCK_ENABLE |= 0x08;
		//Setting pins PD6 and PD7 to be controlled by a peripheral mode (UART2)
	GPIOAFSEL_ALTFUNCTION_CONTROL |= 0xC0;
	
	//Selecting the UART perihparal mode for pins PA0 and PA1
	//GPIOPCTL_ALTFUNCTION_SELECT |= (1<<24) | (1<<28);
	/*GPIOPCTL_ALTFUNCTION_SELECT = (1<<24);
	GPIOPCTL_ALTFUNCTION_SELECT = (1<<28);*/
	//Selecting the UART peripheral mode for pins PD6 and PD7
	GPIOPCTL_ALTFUNCTION_SELECT = (GPIOPCTL_ALTFUNCTION_SELECT&0x00FFFFFF) + 0x11000000;
		//Enabling the digital I/O for pins PD6 and PD7
	GPIODEN_DIGITAL_PIN_ENABLE |= 0xC0;


	//Disabling the UARTEN pin in this register so I can set the baud rate and serial parameters
	UARTCTL_UART_ENABLE_DISABLE &= ~(0x01);	
	//Writing the integer part as 104 of the baud rate to make it 9600bps
	UARTIBRD_UART_BAUDRATE_INTEGER = 104;
	//Writing the decimal part as 11 of the baud rate to make it 9600bps
	UARTFBRD_UART_BAUDRATE_FRACTIONAL = 11;
	//Setting up the serial parameter here as 8-bit, no parity, and 1 stop-bit
	UARTLCRH_SERIAL_PARAMETERS = (0x3<<5);
	//Setting up the baud clock source as "system clock"
	UARTCC_UART_CLOCK_SOURCE = 0x00;
	
	//Enabling the UARTEN pin this register
	UARTCTL_UART_ENABLE_DISABLE |= (1<<0) | (1<<8) | (1<<9);
	//UARTCTL_UART_ENABLE_DISABLE |= 0x00000001; 
	//Disabling the analog function on pins D6 and D7
	GPIOAMSEL_GPIO_ANALOG_ENABLE_DISABLE &= ~0xC0; 
}

void LED_Config (void)
{
	//Enabling the clock to PORTF
	RCGC2_GPIO_PORTF |= (1<<5); 
	//Setting pins PF1, PF2, and PF3 as outputs for the LED's attached to these pins
	GPIODIR_DIR_PORTF = (1<<1) | (1<<2) | (1<<3);
	//Enabling the digital functions on the LED pins
	GPIODEN_DIGITAL_ENABLE_PORTF = (1<<1) | (1<<2) | (1<<3);
	//Turns off the LED's
	GPIO_PORTF_DATA &= ~((1<<1) | (1<<2) | (1<<3)); 
}

char readChar (void)
{
	char c;
	while ((UARTFR_Flag_Register & (1<<4)) != 0);
	c = UARTDR_FIFO_DATA_REGISTER;
	return c;
}

void printChar (char c)
{
	while ((UARTFR_Flag_Register & (1<<5)) != 0);
	UARTDR_FIFO_DATA_REGISTER = c;
}

void printString (char *string)
{
	while(*string)
	{
		printChar(*(string++));
	}
}