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问题：MSP430中C语言问题
描述:
完全代码如下：
/*
* main.c
*/
#include <msp430.h>
#include <stdint.h>
typedef struct //以指针形式定义P8口的各个寄存器
{
const volatile uint8_t* PxIN; //定义一个不会被编译的无符号字符型变量
volatile uint8_t* PxOUT;
volatile uint8_t* PxDIR;
volatile uint8_t* PxREN;
volatile uint8_t* PxSEL;
} GPIO_TypeDef;
const GPIO_TypeDef GPIO4 =
{ &P4IN, &P4OUT, &P4DIR, &P4REN, &P4SEL};
const GPIO_TypeDef GPIO5 =
{&P5IN, &P5OUT, &P5DIR, &P5REN, &P5SEL};
const GPIO_TypeDef GPIO8 =
{&P8IN, &P8OUT, &P8DIR, &P8REN, &P8SEL};
const GPIO_TypeDef* LED_GPIO[5] = {&GPIO4, &GPIO4, &GPIO4, &GPIO5, &GPIO8};
const uint8_t LED_PORT[5] = {BIT5, BIT6, BIT7, BIT7, BIT0};
int main( void )
{
// Stop watchdog timer to prevent time out reset
WDTCTL = WDTPW + WDTHOLD;
while(BAKCTL & LOCKIO) // Unlock XT1 pins for operation
BAKCTL &= ~(LOCKIO);
UCSCTL6 &= ~XT1OFF; //启动XT1
while (UCSCTL7 & XT1LFOFFG) //等待XT1稳定
UCSCTL7 &= ~(XT1LFOFFG);
UCSCTL4 = SELA__XT1CLK + SELS__REFOCLK + SELM__REFOCLK; //时钟设为XT1，频率较低，方便软件延时
int i;
for(i=0;i<5;++i)
*LED_GPIO[i]->PxDIR |= LED_PORT[i]; //设置各LED灯所在端口为输出方向
P4REN |= 0x1F; //使能按键端口上的上下拉电阻
P4OUT |= 0x1F; //上拉状态
uint8_t last_btn = 0x1F, cur_btn, temp;
while(1)
{
cur_btn = P4IN & 0x1F;
temp = (cur_btn ^ last_btn) & last_btn; //找出刚向下跳变的按键
last_btn = cur_btn;
int i;
for(i=0;i<5;++i)
if(temp & (1 << i))
*LED_GPIO[i]->PxOUT ^= LED_PORT[i]; //翻转对应的LED
__delay_cycles(3276); //延时大约100ms
}
}
描述:
c语言指针
时间总是过得那么快，转眼就从大一变到了大三，丢了两年的C语言，现在突然学起430来，发现好多东西都不会，亡羊补牢，未为晚矣！重现在开始，一天攻克一点难题，希望能用这个学期自学430，暑假能有个地方实习，在用GPIO控制LED的时候遇到这么一行代码：*LED_GPIO[i]->PxDIR |= LED_PORT[i];//设置各LED灯所在端口为输出方向 虽然有注释，但不是很能理解，希望有人能帮忙解答一下，谢谢！完全代码如下：
/*
* main.c
*/
#include <msp430.h>
#include <stdint.h>
typedef struct //以指针形式定义P8口的各个寄存器
{
const volatile uint8_t* PxIN; //定义一个不会被编译的无符号字符型变量
volatile uint8_t* PxOUT;
volatile uint8_t* PxDIR;
volatile uint8_t* PxREN;
volatile uint8_t* PxSEL;
} GPIO_TypeDef;
const GPIO_TypeDef GPIO4 =
{ &P4IN, &P4OUT, &P4DIR, &P4REN, &P4SEL};
const GPIO_TypeDef GPIO5 =
{&P5IN, &P5OUT, &P5DIR, &P5REN, &P5SEL};
const GPIO_TypeDef GPIO8 =
{&P8IN, &P8OUT, &P8DIR, &P8REN, &P8SEL};
const GPIO_TypeDef* LED_GPIO[5] = {&GPIO4, &GPIO4, &GPIO4, &GPIO5, &GPIO8};
const uint8_t LED_PORT[5] = {BIT5, BIT6, BIT7, BIT7, BIT0};
int main( void )
{
// Stop watchdog timer to prevent time out reset
WDTCTL = WDTPW + WDTHOLD;
while(BAKCTL & LOCKIO) // Unlock XT1 pins for operation
BAKCTL &= ~(LOCKIO);
UCSCTL6 &= ~XT1OFF; //启动XT1
while (UCSCTL7 & XT1LFOFFG) //等待XT1稳定
UCSCTL7 &= ~(XT1LFOFFG);
UCSCTL4 = SELA__XT1CLK + SELS__REFOCLK + SELM__REFOCLK; //时钟设为XT1，频率较低，方便软件延时
int i;
for(i=0;i<5;++i)
*LED_GPIO[i]->PxDIR |= LED_PORT[i]; //设置各LED灯所在端口为输出方向
P4REN |= 0x1F; //使能按键端口上的上下拉电阻
P4OUT |= 0x1F; //上拉状态
uint8_t last_btn = 0x1F, cur_btn, temp;
while(1)
{
cur_btn = P4IN & 0x1F;
temp = (cur_btn ^ last_btn) & last_btn; //找出刚向下跳变的按键
last_btn = cur_btn;
int i;
for(i=0;i<5;++i)
if(temp & (1 << i))
*LED_GPIO[i]->PxOUT ^= LED_PORT[i]; //翻转对应的LED
__delay_cycles(3276); //延时大约100ms
}
}