Cortex_M0 LPC11C14 GPIO（二）

通过LED灯实验，学习LPC11C14的GPIO模块。

首先查看FS_11C14开发板的电路图，查看LED灯的连接方式

从电路图中可以看出，当LED1( LED2 )引脚给低电平时，LDE1( LED2 )灯导通

LED1、LED2两个引脚又分别连接了处理器的PIO3_0和 PIO3_1两个引脚

所以点亮LED1需要PIO3_0输出低电平，点亮LED2要PIO3_1输出低电平。

主程序如下
        int main(void)
        {
                unsigned int          i;
                SystemInit();
                GPIOInit();
                // LED
                GPIOSetDir(PORT3, 0, 1);                       // Set PIO3_0 to output
                GPIOSetValue(PORT3, 0, 1);                  // PIO3_0 output 1, Turn off LED1
                while(1)                          /* Loop forever */
                {
                        for(i=0; i<250000; i++);
                        GPIOSetValue(PORT3, 0, 0);
                        for(i=0; i<250000; i++);
                        GPIOSetValue(PORT3, 0, 1);
                }
        }

出程序中主要是通过GPIOSetValue(PORT3, 0, 0)和GPIOSetValue(PORT3, 0, 1)分别控制PIO3_0和PIO3_1引脚的输出。

GPIOSetValue() 函数如下
        /*****************************************************************************
        ** Function name:            GPIOSetValue
        **
        ** Descriptions:                Set/clear a bitvalue in a specific bit position
        **                                                   in GPIO portX(X is the port number.)
        **
        ** parameters:                           port num, bit position, bit value
        ** Returned value:           None
        **
        *****************************************************************************/
        void GPIOSetValue( uint32_t portNum, uint32_t bitPosi, uint32_t bitVal )
        {
                 LPC_GPIO[portNum]->MASKED_ACCESS[(1<<bitPosi)] = (bitVal<<bitPosi);
        }

LPC_GPIO的定义：

static LPC_GPIO_TypeDef (* const LPC_GPIO[4]) = { LPC_GPIO0, LPC_GPIO1, LPC_GPIO2, LPC_GPIO3 };
        可以看出LPC_GPIO[] 是一个指针数组，里面存放的内容为LPC_GPIO0, LPC_GPIO1, LPC_GPIO2, LPC_GPIO3。

在LPC11xx.h中定义
        #define LPC_GPIO0 ((LPC_GPIO_TypeDef *) LPC_GPIO0_BASE )
        #define LPC_GPIO1 ((LPC_GPIO_TypeDef *) LPC_GPIO1_BASE )
        #define LPC_GPIO2 ((LPC_GPIO_TypeDef *) LPC_GPIO2_BASE )
        #define LPC_GPIO3 ((LPC_GPIO_TypeDef *) LPC_GPIO3_BASE )

可以很容易看出，LPC_GPIO0, LPC_GPIO1, LPC_GPIO2, LPC_GPIO3分别为GPIO端口特殊功能寄存器的基地址。

typedef struct
        {
                union {
                        __IO uint32_t MASKED_ACCESS[4096]; /*!< Offset: 0x0000 to 0x3FFC Port data Register for pins PIOn_0 to PIOn_11 (R/W) */
                        struct {
                                uint32_t RESERVED0[4095];
                                __IO uint32_t DATA; /*!< Offset: 0x3FFC Port data Register (R/W) */
           &nbsnbsp;            };
                };
                uint32_t RESERVED1[4096];
                __IO uint32_t DIR; /*!< Offset: 0x8000 Data direction Register (R/W) */
                __IO uint32_t IS; /*!< Offset: 0x8004 Interrupt sense Register (R/W) */
                __IO uint32_t IBE; /*!< Offset: 0x8008 Interrupt both edges Register (R/W) */
                __IO uint32_t IEV; /*!< Offset: 0x800C Interrupt event Register (R/W) */
                __IO uint32_t IE; /*!< Offset: 0x8010 Interrupt mask Register (R/W) */
                __IO uint32_t RIS; /*!< Offset: 0x8014 Raw interrupt status Register (R/ ) */
                __IO uint32_t MIS; /*!< Offset: 0x8018 Masked interrupt status Register (R/ ) */
                __IO uint32_t IC; /*!< Offset: 0x801C Interrupt clear Register (R/W) */
        } LPC_GPIO_TypeDef;
        /*@}*/ /* end of group LPC11xx_GPIO */

通过LPC_GPIO[portNum]->MASKED_ACCESS[(1<<bitPosi)] = (bitVal<<bitPosi);给相应地址内的寄存器写值 从而实现了对应端口的输出电平