(轉)Cortex-M3 (NXP LPC1788)之IIC應用--PCA9532進行IO擴展和LED亮度控制

 PCA9532是一個I2C接口的設備，可以用於IO的擴展和LED的亮度調節。它內部集成了振盪器，可以輸出2路用戶可編程的PWM波，周期從6.58ms到1.69S。16路的輸出，可以設置成輸出高低電平以及PWM波輸出。

        做為從設備，他的8位地址的高四位固定為1100，最低位為數據的方向位，剩下的3位有硬件連線確定他的地址。PCA9532共有10個寄存器來配置他的輸出狀態。

其中INPUT0 INPUT1在管腳配置成普通IO時候用於讀入IO腳的狀態。PSC0 PWM0 PSC1 PWM1用於設置兩路PWM波的周期和占空比。LS0~LS3用於選擇每個管腳的功能，包括通用LED OFF、LED ON、 PWM0、 PWM1。

        知道了需要配置的寄存器，那怎么通過I2C通信來配置這幾個寄存器呢？當LPC1788發出PCA9532的地址得到應答后，需要發送一個字節的數據用於配置控制寄存器，他們第四位為B3~B0位，比如發送的字節第4位為0，即B3~B0為0則他接下去收到的數據用來配置INPUT0。配置寄存器的第4位為AI,即autoincrease，表示接收到一個字節的配置數據后，是否自動的將B3~B0加1，方便配置下一個表中的寄存器。

        開發板上的PCA9532的電路圖如下

        程序中配置LED0~7為GPIO用於檢測按鍵，LED8~LED11配置成PWM輸出，將LED RED做出漸亮漸暗的效果，LED12~LED15根據按鍵值設置成LED ON 或LED OFF。按鍵值讀取PCA9532的INPUT0得到。程序如下

#define PCLK    60000000
#define I2C0SCK  100000
#define PCA9532_ADDRESS 0x60

#define rI2C0CONSET (*(volatile unsigned*)(0x4001C000))
#define rI2C0CONCLR (*(volatile unsigned*)(0x4001C018))
#define rI2C0STAT   (*(volatile unsigned*)(0x4001C004))
#define rI2C0DAT    (*(volatile unsigned*)(0x4001C008))
#define rI2C0SCLH   (*(volatile unsigned*)(0x4001C010))
#define rI2C0SCLL   (*(volatile unsigned*)(0x4001C014))

#define rIOCON_P0_27    (*(volatile unsigned *)(0x4002C06C))
#define rIOCON_P0_28    (*(volatile unsigned *)(0x4002C070))

#define rPCONP      (*(volatile unsigned*)(0x400FC0C4))

unsigned char config[11], read_data[1];
void I2C0_Init()
{
    rIOCON_P0_27 = (rIOCON_P0_27&(~0x7))|0x1;   //I2C0_SDA
    rIOCON_P0_28 = (rIOCON_P0_28&(~0x7))|0x1;   //I2C0_SCL
    rPCONP |= 0x1<<7;   //I2C0 Power Enable
    rI2C0SCLH = PCLK/I2C0SCK/2;                 //set I2C0 frequency 100khz
    rI2C0SCLL = PCLK/I2C0SCK/2;
    rI2C0CONSET |= 0x1<<6;                       //I2C接口使能
    rI2C0CONCLR = 0x1<<3|0x1<<5;                //清除SI STA
}

unsigned char I2C0_Start()
{
    rI2C0CONCLR = 0x1<<3;               //清除SI標志

    rI2C0CONSET |= 0x1<<5;              //置位STA進入主發送模式

    while(!(rI2C0CONSET&(0x1<<3)));     //起始條件發送完成

    rI2C0CONCLR = 0x1<<5;               //清除STA標志

    return (rI2C0STAT&0xF8);
}

void I2C0_Stop()
{
    rI2C0CONCLR = 0x1<<5;               //清除STA標志
    rI2C0CONSET |= 0x1<<4;              //發送STO標志
    rI2C0CONCLR = 0x1<<3;               //清除SI標志
}

unsigned char I2C0_SentByte(unsigned char data)
{
    rI2C0DAT = data;

    rI2C0CONCLR = 0x1<<3;               //清除SI標志

    while(!(rI2C0CONSET&(0x1<<3)));     //發送完數據得到了應答

    return (rI2C0STAT&0xF8);
}

unsigned char I2C0_GetByte(unsigned char* data, unsigned char ack_flag)
{
    if(ack_flag)
    {
        rI2C0CONSET |= 0x1<<2;              //主接收模式，接收到一個字節返回應答
    }
    else
    {
        rI2C0CONCLR = 0x1<<2;               //主接收模式，接收最后一個字節時，不返回應答
    }
    rI2C0CONCLR = 0x1<<3;                   //清除SI標志
    while(!(rI2C0CONSET&(0x1<<3)));         //發送完數據得到了應答
    *data = (unsigned char)rI2C0DAT;
    return (rI2C0STAT&0xF8);
}

int I2C0_MasterTransfer(unsigned char slave_address, unsigned char *transfer_data, unsigned int transfer_count,\
                    unsigned char *receive_data, unsigned int receive_count)
{
    unsigned char status;
    unsigned int i;

    status = I2C0_Start();
    while(status != 0x08);

    status = I2C0_SentByte(slave_address<<1);
    while(status != 0x18);

    for(i=0; i<transfer_count; i++)
    {
        status = I2C0_SentByte(*(transfer_data+i));
        while(status != 0x28);
    }

    if(receive_data!=(void*)0 && receive_count!=0)
    {
        //進入主接收模式
        status = I2C0_Start();
        while(status != 0x10);

        status = I2C0_SentByte((slave_address<<1)|0x1);
        while(status != 0x40);

        for(i=0; i<receive_count; i++)
        {
            if(i<receive_count-1)
            {
                status = I2C0_GetByte(receive_data, 1);
                while(status != 0x50);
            }
            else
            {
                status = I2C0_GetByte(receive_data, 0);
                while(status != 0x58);
            }
            receive_data++;
        }
    }


    I2C0_Stop();

    return 1;
}

void PCA9532_Config()
{
    config[0] = 0x1<<4;     //讀寫控制寄存器后低四位自動增加
    config[1] = 0;          //input0
    config[2] = 0;          //input1
    config[3] = 0;          //PSC0    PWM0的周期6.5ms
    config[4] = 0;          //PWM0    PWM0占空比設置成0%
    config[5] = 0;          //PSC1    PWM1的周期為6.5ms
    config[6] = 0;          //PWM1    PWM1占空比設置成0%
    config[7] = 0;          //LS0
    config[8] = 0;          //LS1     LED0~7 設置成GPIOS
    config[9] = 0xFA;       //LS2     11111010, LED8,9->blinks PWM0; LED10,11->blinks PWM1
    config[10] = 0;         //LS3     LED12~LED15, LED off

}


int main(void)
{
    unsigned char flag=1, data=0;
    unsigned int i;
    I2C0_Init();
    PCA9532_Config();
    while(1)
    {
        I2C0_MasterTransfer(PCA9532_ADDRESS, config, sizeof(config), 0, 0);

        I2C0_MasterTransfer(PCA9532_ADDRESS, &data, 1, read_data, 1);

        if(flag)
        {
            config[4]++;
            config[6]++;
        }
        else
        {
            config[4]--;
            config[6]--;
        }

        if(config[4]==255 || config[4]==0)
        {
            flag = !flag;
        }

        for(i=0; i<4; i++)
        {
            if(read_data[0]&(0x1<<i))
            {
                config[10] &= ~(0x3<<(i*2));

            }
            else
            {
                config[10] |= (0x1<<(i*2));
            }
        }

    }
}
程序調試過程中遇到如下問題，要注意：        1,I2C控制清除寄存器為只讀，因此不能進行|=操作，否則狀態寄存器的值異常。不知道為什么不是產生異常復位，之前EEPROM也對只讀寄存器進行該操作會產生系統異常進入異常中斷。        2，在主發送模式切換到主接收模式的過程中，一定要先清除SI標志。開始沒注意，發送重復起始表示后的狀態一直是0x28，把這個重復起始標志單數據發送？