CCS5.4+Proteus8的F28027实践课十三、I2C

今晚我们来学习I2C的编程，呵呵，还是老规矩，最简单的非中断回环测试。

先来总体看下寄存器结构





其实对于我们今晚的主题来讲，主要用到了I2COAR、I2CSTR、I2CCLKL、I2CCLKH、I2CDRR、I2CDXR、I2CMDR、I2CPSC这几个寄存器，详细的寄存器介绍大家自己下去看，我们就不浪费时间说这个了。

然后我们来理一下操作步骤：

1、使能外设I2C时钟（这步非常重要，也很容易忽略）；

2、在复位状态下，设置I2C时钟PSC、I2CCLKL、I2CCLKH，还要设置地址信息和回环模式；

3、使能I2C；

4、设置I2C相关引脚；

5、编写发送和接收函数，在这里需要注意的是，TRX这位的值，当为0时，是接收模式；为1时，是发送模式；

好了，思路大概就这样，刚刚去写程序测试了一把，是OK的，我直接贴程序了

首先是I2C的初始化函数

void InitI2C()
{
EALLOW;

SysCtrlRegs.PCLKCR0.bit.I2CAENCLK = 1;

I2caRegs.I2COAR=0x003f;  //7-bit addressing

I2caRegs.I2CMDR.bit.IRS = 0;
I2caRegs.I2CMDR.bit.DLB=1;

I2caRegs.I2CPSC.all = 5;   //  7M <= 60M/(PSC+1)  <=12M
I2caRegs.I2CCLKL = 15;
I2caRegs.I2CCLKH = 15;
I2caRegs.I2CMDR.bit.IRS = 1;

EDIS;
}

然后是GPIO引脚设置

void InitI2CGpio()
{

EALLOW;

/* Enable internal pull-up for the selected pins */
// Pull-ups can be enabled or disabled disabled by the user.
// This will enable the pullups for the specified pins.
// Comment out other unwanted lines.

GpioCtrlRegs.GPAPUD.bit.GPIO28 = 0;    // Enable pull-up for GPIO28 (SDAA)
GpioCtrlRegs.GPAPUD.bit.GPIO29 = 0;       // Enable pull-up for GPIO29 (SCLA)

//    GpioCtrlRegs.GPBPUD.bit.GPIO32 = 0;    // Enable pull-up for GPIO32 (SDAA)
//    GpioCtrlRegs.GPBPUD.bit.GPIO33 = 0;       // Enable pull-up for GPIO33 (SCLA)

/* Set qualification for selected pins to asynch only */
// This will select asynch (no qualification) for the selected pins.
// Comment out other unwanted lines.

GpioCtrlRegs.GPAQSEL2.bit.GPIO28 = 3;  // Asynch input GPIO28 (SDAA)
GpioCtrlRegs.GPAQSEL2.bit.GPIO29 = 3;  // Asynch input GPIO29 (SCLA)

//    GpioCtrlRegs.GPBQSEL1.bit.GPIO32 = 3;  // Asynch input GPIO32 (SDAA)
//  GpioCtrlRegs.GPBQSEL1.bit.GPIO33 = 3;  // Asynch input GPIO33 (SCLA)

/* Configure I2C pins using GPIO regs*/
// This specifies which of the possible GPIO pins will be I2C functional pins.
// Comment out other unwanted lines.

GpioCtrlRegs.GPAMUX2.bit.GPIO28 = 2;   // Configure GPIO28 for SDAA operation
GpioCtrlRegs.GPAMUX2.bit.GPIO29 = 2;   // Configure GPIO29 for SCLA operation

//    GpioCtrlRegs.GPBMUX1.bit.GPIO32 = 1;   // Configure GPIO32 for SDAA operation
//    GpioCtrlRegs.GPBMUX1.bit.GPIO33 = 1;   // Configure GPIO33 for SCLA operation

EDIS;
}

然后是I2C发送子程序

void I2C_WriteData(unsigned char data)
{
I2caRegs.I2CSAR = 0X003f;
I2caRegs.I2CMDR.bit.MST = 1;
I2caRegs.I2CMDR.bit.TRX = 1;
I2caRegs.I2CMDR.bit.STT = 1;
I2caRegs.I2CMDR.bit.STP = 1;

while(I2caRegs.I2CSTR.bit.BB!=1);
I2caRegs.I2CDXR = data;
}

接着是接收子程序

unsigned char I2C_ReadData()
{
unsigned char data;
I2caRegs.I2CMDR.bit.TRX = 0;
I2caRegs.I2CMDR.bit.STT = 1;
I2caRegs.I2CMDR.bit.STP = 1;
while(I2caRegs.I2CSTR.bit.RRDY!=1);
data = I2caRegs.I2CDRR&0x00ff;
return data;
}

最后是主函数

void main(void)
{

// Step 1. Initialize System Control:
// PLL, WatchDog, enable Peripheral Clocks
// This example function is found in the DSP2802x_SysCtrl.c file.
InitSysCtrl();

// Step 2. Initalize GPIO:
// This example function is found in the DSP2802x_Gpio.c file and
// illustrates how to set the GPIO to it's default state.
InitGpio();

// Step 3. Clear all interrupts and initialize PIE vector table:
// Disable CPU interrupts
DINT;

// Initialize PIE control registers to their default state.
// The default state is all PIE interrupts disabled and flags
// are cleared.
// This function is found in the DSP2802x_PieCtrl.c file.
InitPieCtrl();

// Disable CPU interrupts and clear all CPU interrupt flags:
IER = 0x0000;
IFR = 0x0000;

// Initialize the PIE vector table with pointers to the shell Interrupt
// Service Routines (ISR).
// This will populate the entire table, even if the interrupt
// is not used in this example.  This is useful for debug purposes.
// The shell ISR routines are found in DSP2802x_DefaultIsr.c.
// This function is found in DSP2802x_PieVect.c.
InitPieVectTable();

// Step 4. Initialize all the Device Peripherals:
// This function is found in DSP2802x_InitPeripherals.c
// InitPeripherals(); // Not required for this example

// Step 5. User specific code:

InitI2C();
InitI2CGpio();
InitLCD12864();

WRITECMD_LCD12864(0x93);

I2C_WriteData('A');
WRITEDATA_LCD12864(I2C_ReadData());
while(1);
}

程序下载测试结果如图



那到这里，简单的I2C了解就差不多了，大家可以继续发散拓展学习，我也要洗洗睡了，最近几天睡太晚了，白天都快没状态了，不能顾此失彼，鱼和熊掌要兼得，呵呵。

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