mini2440下调试IIC时序问题总结与分析

说明：mini2440平台，wince6.0系统，vs2005

经过几个月的学学停停，终于在wince下加入了GPIO模拟的IIC总线，实现了IIC的移植，IIC的芯片是SHT21温湿度芯片。

之所以搞了这么久没搞定IIC，是在ADS下很早实现了，可就是添加到系统就总不对！示波器抓取发现时序在芯片复位后就不对了，找来找去都不知道怎么回事！这下就陷入了

纠结中，还是那种死循环的纠结，怎么都绕不出来！

网上发帖，网友们也支了很多招，感谢你们！jonsenwu网友的话提示了我！驱动程序加到系统里面，系统的调度需要时间，驱动程序使用的延时会出现延长的情况！根据他的提示，也进一步向他请教，这里特别感谢他！对驱动程序的优先级进行调整，使其在运行过程中始终保持住CPU的使用权。在ADS下测试的延时函数在系统下是不会相同的！

经过这个移植学到的东西：

1、wince下优先级相关知识

以下是代码：用于实现优先级抢占

//dwThreadID = GetCurrentThread(); //获取线程的ID 
//dwThreadPri = CeGetThreadPriority(dwThreadID); //获取线程ID的优先级 
//dwThreadQuantum = CeGetThreadQuantum(dwThreadID); // 获取线程的时间论片参数 
//CeSetThreadPriority(dwThreadID, 0);// 设置当前线程的优先级为最高 
//CeSetThreadQuantum(dwThreadID, 0); //设置当前线程的时间论片为0，保持CPU的占有权 
// 
//.......... （操作i2c的函数） 
// 
//CeSetThreadQuantum(dwThreadID, dwThreadQuantum);  // 恢复正常时间论片 
//CeSetThreadPriority(dwThreadID, dwThreadPri); //恢复正常优先级 

说明：设置优先级有两个函数，一个函数可以设置0~255的个优先级（CeSetThreadPriority（）），一个函数可以只能设置应用程序的优先级248~255（SetThreadPriority（））!!

IIC调试成功后，把数据传给应用程序又出现个问题，先是在XXX_IOControl实现传递，怎么试都没数据出来，最后放到XXX_Read里面来实现就OK了。这里还要说明个关于memcpy的问题。如下：

2、对于memcpy函数的理解

先看一下出问题的写法：

unsigned short  SHT_Data[2];//

memcpy( pBuffer , SHT_Data , 2 );//output

我应用程序读到的数据只有温度是对的，湿度就很大的数！肯定高手一眼就看出来问题所在了！

是因为：memcpy函数的拷贝是基于字节的，上面我拷贝的个数是2，所以只有温度能正常，湿度根本就没拷贝过去。

正确的方法是4个字节：memcpy( pBuffer , SHT_Data , 4);//output

3、GPIO的说明

这里得再次鄙视下友善之臂的技服！GPIO我原来使用的是2440默认两个引脚（默认的接了EEPROM和Camera！！，能对才怪！），最后查找到SPI0的空余引脚才搞定。

代码可以参照：http://www.linuxidc.com/Linux/2012-11/74419p2.htm

在mini2440下用IIC的IO口的模拟IIC时序，驱动一个外设芯片，ADS调试正确，添加到系统就不行，对驱动的优先级也提升了，还是不正确。

volatile IOPreg *s2440IOP = (IOPreg *)IOP_BASE;

//volatile INTreg *s2440INT = (INTreg *)INT_BASE;

float SHT_Data[2];///tmp

HANDLE hDevSHT21;

DWORD SHT2x_Option_ThreadFuc(LPVOID Context);

void Virtual_Alloc(); // Virtual allocation

///////////////////////////////////////////////////////////////////////////

////////////////////////////////I2C.c source///////////////////////////////////////

#define noACK 0

#define aCk 1

#define SCL_OutEnable s2440IOP->rGPECON =( s2440IOP->rGPECON | 0x30000000 ) & 0xDFFFFFFF //28 config SCL as output

#define SDA_OutEnable s2440IOP->rGPECON =( s2440IOP->rGPECON | 0xC0000000 ) & 0x7FFFFFFF //30config SDA as output

#define SDA_OutDisable s2440IOP->rGPECON =( s2440IOP->rGPECON & 0x3fffffff)//config SDA as input

#define SCL_Set s2440IOP->rGPEDAT |= (1 << 14) //SCL output '1'

#define SCL_Clear s2440IOP->rGPEDAT &= ~(1 << 14) //SCL output '0'

#define SDA_Set s2440IOP->rGPEDAT |= (1 << 15) //SDA output '1'

#define SDA_Clear s2440IOP->rGPEDAT &= ~(1 << 15)

void Delay_us(U32 uS)

{

volatile DWORD dwCounter;

dwCounter = 100 * uS;

while(dwCounter--);

}

void I2c_Initialize ()

{ // put setup code here

SCL_OutEnable; // set gpio6->SCL as output

SCL_Set; // set SCL = '1'

SDA_OutDisable; // set gpio7->SDA as input

SDA_Set;

Delay_us(100); // let I2C device ready

}

//==============================================================================

void I2c_StartCondition ()

//==============================================================================

{

SDA_OutEnable; // set SDA as output

//SCL_OutEnable; //!!

SDA_Set;

SCL_Set;

Delay_us(1);

SDA_Clear;

Delay_us(5);

SCL_Clear;

Delay_us(5);

}

//==============================================================================

void I2c_StopCondition ()

//==============================================================================

{

SDA_OutEnable; // set SDA as output

//SCL_OutEnable; //!!

SDA_Clear;

SCL_Clear;

Delay_us(1);

SCL_Set;

Delay_us(5);

SDA_Set;

Delay_us(5);

}

//----------------------------------------------------------------------------------

unsigned char I2c_WriteByte(unsigned char value)

// writes a byte on the Sensibus and checks the acknowledge

//----------------------------------------------------------------------------------

{

// dwThreadID = GetCurrentThread();

//dwThreadPri = CeGetThreadPriority(dwThreadID);

//dwThreadQuantum = CeGetThreadQuantum(dwThreadID);

//CeSetThreadPriority(dwThreadID, 0);/

//CeSetThreadQuantum(dwThreadID, 0);

//

//。。。。。。。 （此部分是操作i2c的函数）

//

//CeSetThreadQuantum(dwThreadID, dwThreadQuantum);

//CeSetThreadPriority(dwThreadID, dwThreadPri);

HANDLE dwThreadID = GetCurrentThread();

DWORD dwThreadPri = CeGetThreadPriority(dwThreadID);

DWORD dwThreadQuantum = CeGetThreadQuantum(dwThreadID);

CeSetThreadPriority(dwThreadID, 0);

CeSetThreadQuantum(dwThreadID, 0);

int error=0, i1=0, i2=0;

for(i2 = 0; i2 < 8; i2++ )

{ // setup data onto SDA

if(value & 0x80){

SDA_Set; //SetSDA( 1 );

}

else{

SDA_Clear; //SetSDA( 0 );

}

Delay_us(1); //I2C timing: data setup time > 200ns

// issue a clock

SCL_Set; //SetSCL( 1 );

Delay_us(1); //I2C timing: SCL high time > 0.6us

SCL_Clear; //SetSCL( 0 );

Delay_us(2); //I2C timing: SCL low time > 1.3us

value= value<< 1;

}

//check ACK(Low state) from I2C device

SDA_OutDisable; //set SDA as input

Delay_us(1); //I2C timing: data(from I2C device) setup time > 200ns

SCL_Set; //SetSCL( 1 ); // issue a clock

Delay_us(1); //I2C timing: SCL high time > 0.6us

if(s2440IOP->rGPEDAT>>15) //read ACK_BIT issued from I2C device

{

// NO ACK, so setup STOP condition

SCL_Set; //SetSCL( 1 );

Delay_us(1); //I2C timing: stop setup timing > 0.6us

SDA_Set; //SetSDA( 1 ); SDA is in input status!

return -(i1+1); // no acknowledgement -> failed

}

SCL_Clear; //SetSCL( 0 );

Delay_us(2); //I2C timing: SCL low time > 1.3us

//check ACK passed, config SDA as output for further outputing

SDA_OutEnable;

// backup the thread priority;

CeSetThreadQuantum(dwThreadID, dwThreadQuantum);

CeSetThreadPriority(dwThreadID, dwThreadPri);

return 0;

}

//----------------------------------------------------------------------------------

unsigned char I2c_ReadByte(unsigned char ack)

//----------------------------------------------------------------------------------

// reads a byte form the Sensibus and gives an acknowledge in case of 'ack=1'

{

HANDLE dwThreadID = GetCurrentThread();

DWORD dwThreadPri = CeGetThreadPriority(dwThreadID);

DWORD dwThreadQuantum = CeGetThreadQuantum(dwThreadID);

CeSetThreadPriority(dwThreadID, 0);

CeSetThreadQuantum(dwThreadID, 0);

unsigned char i,val=0;

int i2=0,ub[1];

SDA_OutDisable; //SetSDADir( 0 ); // set SDA as input

// then read a abyte

for(i2 = 0; i2 < 8; i2++)

{

ub[0] = ub[0] << 1;

// issue a clock

SCL_Set; //SetSCL( 1 );

//DelayInuSec(1); //I2C timing: SCL high time > 0.6us

if(s2440IOP->rGPEDAT>>15) // read SDA

{

ub[0] = ub[0] | 0x01;

}

SCL_Clear; //SetSCL( 0 );

Delay_us(5); //I2C timing: SCL low time > 1.3us

}

//issue ACK condition properly

SDA_OutEnable;

if (ack)

{ SDA_Clear; }

else

{ SDA_Set; }

Delay_us(1); //I2C timing: data setup time > 200ns

SCL_Set; //SetSCL( 1 );

Delay_us(1); //I2C timing: SCL high time > 0.6us

SCL_Clear;

Delay_us(2); //I2C timing: SCL low time > 1.3us

// backup the thread priority;

CeSetThreadQuantum(dwThreadID, dwThreadQuantum);

CeSetThreadPriority(dwThreadID, dwThreadPri);

return ub[0];

}

///////////////////////////// SHT2x.c source //////////////////////////////////////

//===========================================================================

unsigned char SHT2x_MeasureHM(etSHT2xMeasureType eSHT2xMeasureType, unsigned int *pMeasurand)

//===========================================================================

{

unsigned char checksum; //checksum

unsigned char data[2]; //data array for checksum verification

unsigned char error=0; //error variable

unsigned int i; //counting variable

//-- write I2C sensor address and command --

I2c_StartCondition();

error |= I2c_WriteByte (I2C_ADR_W); // I2C Adr 0x80

RETAILMSG(1,(TEXT(' ...I2c_WriteByte (I2C_ADR_W ) error=%d rn'),error));

error = 0;

switch(eSHT2xMeasureType)

{

case HUMIDITY:

error |= I2c_WriteByte (TRIG_RH_MEASUREMENT_HM); break; //0xe5

case TEMP :

error |= I2c_WriteByte (TRIG_T_MEASUREMENT_HM); break; //0xe3

default:

break;

}

//-- wait until hold master is released --

RETAILMSG(1,(TEXT(' ...The MEASUREMENT error=%d rn'),error));

error = 0;

I2c_StartCondition();

error |= I2c_WriteByte (I2C_ADR_R);//0x81

RETAILMSG(1,(TEXT(' ...I2c_WriteByte (I2C_ADR_R) error =%d rn'),error));

error = 0;

Delay_us(2400);//covert time 90ms

//-- read two data bytes and one checksum byte --

data[0] = I2c_ReadByte(ACK);

data[1] = I2c_ReadByte(ACK);

checksum=I2c_ReadByte(NO_ACK);

RETAILMSG(1,(TEXT(' ...the MSB is 0x%xrn'), data[0]));

RETAILMSG(1,(TEXT(' ...the LSB is 0x%xrn'), data[1]));

*pMeasurand=data[0];

*pMeasurand<<=8;

*pMeasurand+=data[1];

//-- verify checksum --

//error |= SHT2x_CheckCrc (data,2,checksum);

I2c_StopCondition();

return error;

}

//===========================================================================

u8 SHT2x_SoftReset()

//===========================================================================

{

u8 error=0; //error variable

I2c_StartCondition();

error |= I2c_WriteByte (I2C_ADR_W); // I2C Adr 0x80

error |= I2c_WriteByte (SOFT_RESET); //0xfe // Command

I2c_StopCondition();

//Delay_us(400); // wait till sensor has restarted

Sleep(15);

return error;

}

//void SHT2x_Option(unsigned int pValue[] )

DWORD SHT2x_Option_ThreadFuc(LPVOID Context)

{

int error=0;

unsigned int sRH,sT;

float fHumiValue,fTempeValue;

LPCRITICAL_SECTION RegCS; // Register CS

while(1)

{

// EnterCriticalSection(RegCS);