(转)CortexM3 (NXP LPC1788)之IIC应用PCA9532进行IO扩展和LED亮度控制

 PCA9532是一个I2C接口的设备，可以用于IO的扩展和LED的亮度调节。它内部集成了振荡器，可以输出2路用户可编程的PWM波，周期从6.58ms到1.69S。16路的输出，可以设置成输出高低电平以及PWM波输出。

        做为从设备，他的8位地址的高四位固定为1100，最低位为数据的方向位，剩下的3位有硬件连线确定他的地址。PCA9532共有10个寄存器来配置他的输出状态。

其中INPUT0 INPUT1在管脚配置成普通IO时候用于读入IO脚的状态。PSC0 PWM0 PSC1 PWM1用于设置两路PWM波的周期和占空比。LS0~LS3用于选择每个管脚的功能，包括通用LED OFF、LED ON、 PWM0、 PWM1。

        知道了需要配置的寄存器，那怎么通过I2C通信来配置这几个寄存器呢？当LPC1788发出PCA9532的地址得到应答后，需要发送一个字节的数据用于配置控制寄存器，他们第四位为B3~B0位，比如发送的字节第4位为0，即B3~B0为0则他接下去收到的数据用来配置INPUT0。配置寄存器的第4位为AI,即autoincrease，表示接收到一个字节的配置数据后，是否自动的将B3~B0加1，方便配置下一个表中的寄存器。

        开发板上的PCA9532的电路图如下

        程序中配置LED0~7为GPIO用于检测按键，LED8~LED11配置成PWM输出，将LED RED做出渐亮渐暗的效果，LED12~LED15根据按键值设置成LED ON 或LED OFF。按键值读取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标志

    rI2C0CONSET |= 0x1<<5;              //置位STA进入主发送模式

    while(!(rI2C0CONSET&(0x1<<3)));     //起始条件发送完成

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

    return (rI2C0STAT&0xF8);
}

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

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

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

    while(!(rI2C0CONSET&(0x1<<3)));     //发送完数据得到了应答

    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，接收到一个字节返回应答
    }
    else
    {
        rI2C0CONCLR = 0x1<<2;               //主接收模式，接收最后一个字节时，不返回应答
    }
    rI2C0CONCLR = 0x1<<3;                   //清除SI标志
    while(!(rI2C0CONSET&(0x1<<3)));         //发送完数据得到了应答
    *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)
    {
        //进入主接收模式
        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;     //读写控制寄存器后低四位自动增加
    config[1] = 0;          //input0
    config[2] = 0;          //input1
    config[3] = 0;          //PSC0    PWM0的周期6.5ms
    config[4] = 0;          //PWM0    PWM0占空比设置成0%
    config[5] = 0;          //PSC1    PWM1的周期为6.5ms
    config[6] = 0;          //PWM1    PWM1占空比设置成0%
    config[7] = 0;          //LS0
    config[8] = 0;          //LS1     LED0~7 设置成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));
            }
        }

    }
}
程序调试过程中遇到如下问题，要注意：        1,I2C控制清除寄存器为只读，因此不能进行|=操作，否则状态寄存器的值异常。不知道为什么不是产生异常复位，之前EEPROM也对只读寄存器进行该操作会产生系统异常进入异常中断。        2，在主发送模式切换到主接收模式的过程中，一定要先清除SI标志。开始没注意，发送重复起始表示后的状态一直是0x28，把这个重复起始标志单数据发送？