CH341的I2C接口编程说明

CH341的I2C接口特性：

1、支持I2C速度20K/100K/400K/750K；

2、默认不支持设备的ACK应答监测，即忽略ACK状态；强制支持需修改软件；

引脚序号	功能说明
24	SCL
23	SDA

Windows系统SPI通讯接口函数

HANDLE	WINAPI	CH341OpenDevice(  // 打开CH341设备,返回句柄,出错则无效ULONG			iIndex );  // 指定CH341设备序号,0对应第一个设备VOID	WINAPI	CH341CloseDevice(  // 关闭CH341设备ULONG			iIndex );  // 指定CH341设备序号BOOL	WINAPI	CH341SetStream(  // 设置串口流模式ULONG			iIndex,  // 指定CH341设备序号ULONG			iMode );  // 指定模式,见下行
// 位1-位0: I2C接口速度/SCL频率, 00=低速/20KHz,01=标准/100KHz(默认值),10=快速/400KHz,11=高速/750KHz
// 位2:     SPI的I/O数/IO引脚, 0=单入单出(D3时钟/D5出/D7入)(默认值),1=双入双出(D3时钟/D5出D4出/D7入D6入)
// 位7:     SPI字节中的位顺序, 0=低位在前, 1=高位在前
// 其它保留,必须为0BOOL	WINAPI	CH341ReadI2C(  // 从I2C接口读取一个字节数据ULONG			iIndex,  // 指定CH341设备序号UCHAR			iDevice,  // 低7位指定I2C设备地址UCHAR			iAddr,  // 指定数据单元的地址PUCHAR			oByte );  // 指向一个字节单元,用于保存读取的字节数据BOOL	WINAPI	CH341WriteI2C(  // 向I2C接口写入一个字节数据ULONG			iIndex,  // 指定CH341设备序号UCHAR			iDevice,  // 低7位指定I2C设备地址UCHAR			iAddr,  // 指定数据单元的地址UCHAR			iByte );  // 待写入的字节数据BOOL	WINAPI	CH341StreamI2C(  // 处理I2C数据流,2线接口,时钟线为SCL引脚,数据线为SDA引脚(准双向I/O),速度约56K字节ULONG			iIndex,  // 指定CH341设备序号ULONG			iWriteLength,  // 准备写出的数据字节数PVOID			iWriteBuffer,  // 指向一个缓冲区,放置准备写出的数据,首字节通常是I2C设备地址及读写方向位ULONG			iReadLength,  // 准备读取的数据字节数PVOID			oReadBuffer );  // 指向一个缓冲区,返回后是读入的数据BOOL	WINAPI	CH341ReadEEPROM(  // 从EEPROM中读取数据块,速度约56K字节ULONG			iIndex,  // 指定CH341设备序号EEPROM_TYPE		iEepromID,  // 指定EEPROM型号ULONG			iAddr,  // 指定数据单元的地址ULONG			iLength,  // 准备读取的数据字节数PUCHAR			oBuffer );  // 指向一个缓冲区,返回后是读入的数据BOOL	WINAPI	CH341WriteEEPROM(  // 向EEPROM中写入数据块ULONG			iIndex,  // 指定CH341设备序号EEPROM_TYPE		iEepromID,  // 指定EEPROM型号ULONG			iAddr,  // 指定数据单元的地址ULONG			iLength,  // 准备写出的数据字节数PUCHAR			iBuffer );  // 指向一个缓冲区,放置准备写出的数据

如上API接口函数，根据不通的业务场景可以选用不同的函数。

CH341ReadI2C，CH341WriteI2C：适用于I2C设备地址固定7位，单次读写1个字节。

CH341StreamI2C：适用于多字节的设备地址，或设备地址后紧跟寄存器地址，或连续的多字节读写。

CH341ReadIEEPROM，CH341WriteEEPROM：适用于直接操作EEPROM存储器件。

操作流程：

CH341StreamI2C 函数说明

iWriteLength：I2C Write的字节长度

iWriteBuffer：I2C Write的缓冲区内容，该缓冲区内容会经过SDA信号线对外输出。首字节地址通常是设备地址及读写位。如设备地址是0x50，I2C写操作时首字节为：0x50 << 1 = 0xA0，I2C读操作时首字节为：0x50 << 1 | BIT(0) = 0xA1。

iReadLength：I2C Read的字节长度

oReadBuffer：API成功返回后，其内容是从SDA信号线上采集的数据。

示例1：EEPROM 24C256的设备地址是：0x50，从其3200H开始的地址读取256字节的数据。

UCHAR OutBuf[3] = {0xA1, 0x32, 0x00};
UCHAR InBuf[256];CH341StreamI2C(0, 3, OutBuf, 256, inBuf);

示例2：EEPROM 24C256的设备地址是：0x50，从其3200H开始的地址写入2个字节的数据，内容0x11，0x22。

UCHAR OutBuf[5];OutBuf[0] = 0xA0;
OutBuf[1] = 0x32;
OutBuf[2] = 0x00;
OutBuf[3] = 0x11;
OutBuf[4] = 0x22;CH341StreamI2C(0, 5, OutBuf, 0, NULL);

对应I2C总线时序如下：（未连接真正的EEPROM器件，忽略红色NACK标识）

升级的I2C接口函数

默认库函数提供的I2C函数不支持设备ACK的应答检测，此外有些外设需要在I2C的地址和数据或数据和数据之间插入一定的延迟delay，来满足时序上的要求。此类需求，可参考如下 API的实现。

I2C Start 和 I2C Stop

BOOL	WINAPI	IIC_IssueStart(ULONG			iIndex )  // 指定CH341设备序号
{UCHAR	mBuffer[ mCH341_PACKET_LENGTH ];ULONG	mLength;mBuffer[ 0 ] = mCH341A_CMD_I2C_STREAM;  // 命令码mBuffer[ 1 ] = mCH341A_CMD_I2C_STM_STA;  // 产生起始位mBuffer[ 2 ] = mCH341A_CMD_I2C_STM_END;  // 当前包提前结束mLength = 3;return( CH341WriteData( iIndex, mBuffer, &mLength ) );  // 写出数据块
}BOOL	WINAPI	IIC_IssueStop(ULONG			iIndex )  // 指定CH341设备序号
{UCHAR	mBuffer[ mCH341_PACKET_LENGTH ];ULONG	mLength;mBuffer[ 0 ] = mCH341A_CMD_I2C_STREAM;  // 命令码mBuffer[ 1 ] = mCH341A_CMD_I2C_STM_STO;  // 产生停止位mBuffer[ 2 ] = mCH341A_CMD_I2C_STM_END;  // 当前包提前结束mLength = 3;return( CH341WriteData( iIndex, mBuffer, &mLength ) );  // 写出数据块
}

I2C Write 1个字节并检查应答

BOOL	WINAPI	IIC_OutByteCheckAck(  // 输出一字节数据并检查应答是否有效ULONG			iIndex,  // 指定CH341设备序号UCHAR			iOutByte )  // 准备写出的数据
{UCHAR	mBuffer[ mCH341_PACKET_LENGTH ];ULONG	mLength, mInLen;mBuffer[ 0 ] = mCH341A_CMD_I2C_STREAM;  // 命令码mBuffer[ 1 ] = mCH341A_CMD_I2C_STM_OUT;  // 输出数据,位5-位0为长度,0长度则只发送一个字节并返回应答mBuffer[ 2 ] = iOutByte;  // 数据mBuffer[ 3 ] = mCH341A_CMD_I2C_STM_END;  // 当前包提前结束mLength = 4;mInLen = 0;if ( CH341WriteRead( iIndex, mLength, mBuffer, mCH341A_CMD_I2C_STM_MAX, 1, &mInLen, mBuffer ) ) {  // 执行数据流命令,先输出再输入if ( mInLen && ( mBuffer[ mInLen - 1 ] & 0x80 ) == 0 ) return( TRUE );  // 返回的数据的位7代表ACK应答位,ACK=0有效}return( FALSE );
}

I2C 发送设备地址，等待设备应答（可用于检测设备是否连接，并工作）

BOOL    WINAPI  CH341CheckDev(  //检查I2C设备是否连接ULONG			iIndex,     // 指定CH341设备序号UCHAR           iDevAddr    //设备地址)
{UCHAR buf ;buf = (iDevAddr<<1);IIC_IssueStart(0);if( IIC_OutByteCheckAck(0,buf) ){IIC_IssueStop(0);return TRUE;}else{IIC_IssueStop(0);return FALSE;}
}

CH341StreamI2C_Delay（CH341StreamI2C接口函数的升级版） 可指定I2C连续写数据之间的延时，写地址和读地址之间的延时，读地址和读数据之间的延时，连续读数据之间的延迟。


BOOL WINAPI CH341StreamI2C_Delay(ULONG iIndex,          // 指定CH341设备序号ULONG iWriteLength,    // 准备写出的数据字节数PVOID iWriteBuffer,    // 指向一个缓冲区,放置准备写出的数据,首字节通常是I2C设备地址及读写方向位ULONG iReadLength,     // 准备读取的数据字节数PVOID oReadBuffer,     // 指向一个缓冲区,返回后是读入的数据UCHAR iWriteDataDelay, // 连续写数据之间的延时，单位US，数值范围:0~15UCHAR iAddrDelay1,     // 写地址到读地址之间的延时，单位US，数值范围:0~15UCHAR iAddrDelay2,     // 读地址和读数据的延时，单位US，数值范围:0~15UCHAR iReadDataDelay)  // 连续读数据之间的延时，单位US，数值范围:0~15
{UCHAR mBuffer[mDEFAULT_COMMAND_LEN + mDEFAULT_COMMAND_LEN / 8];ULONG i, j, k, mLength;PUCHAR mWrBuf;UCHAR iWriteTimes;mLength = max(iWriteLength, iReadLength);if (mLength > mMAX_BUFFER_LENGTH)return (FALSE);if (mLength <= mDEFAULT_BUFFER_LEN)mWrBuf = (PUCHAR)mBuffer;                                                               // 不超过默认缓冲区长度else {                                                                                      // 超过则需要另外分配内存mWrBuf = (PUCHAR)LocalAlloc(LMEM_FIXED, mMAX_COMMAND_LENGTH + mMAX_COMMAND_LENGTH / 8); // 分配内存if (mWrBuf == NULL)return (FALSE); // 分配内存失败}i = 0;mWrBuf[i++] = mCH341A_CMD_I2C_STREAM;  // 命令码mWrBuf[i++] = mCH341A_CMD_I2C_STM_STA; // 产生起始位if (iWriteLength) {for (j = 0; j < iWriteLength;) {mLength = mCH341_PACKET_LENGTH - i % mCH341_PACKET_LENGTH; // 当前包剩余长度,<mCH341A_CMD_I2C_STM_MAXif (mLength <= 3) {while (mLength--)mWrBuf[i++] = mCH341A_CMD_I2C_STM_END; // 当前包提前结束mLength = mCH341_PACKET_LENGTH;}if (mLength >= mCH341_PACKET_LENGTH) {mWrBuf[i++] = mCH341A_CMD_I2C_STREAM; // 新包的命令码mLength = mCH341_PACKET_LENGTH - 1;}mLength--; // 去掉尾部的提前结束码if (mLength > 3 * (iWriteLength - j))mLength = 3 * (iWriteLength - j); // 本次输出有效数据长度iWriteTimes = mLength / 3;for (k = 0; k < iWriteTimes; k++) {mWrBuf[i++] = (UCHAR)(mCH341A_CMD_I2C_STM_OUT | 0x01); // 输出数据,位5-位0为长度mWrBuf[i++] = *((PUCHAR)iWriteBuffer + j++);           // 复制数据mWrBuf[i++] = mCH341A_CMD_I2C_STM_US | (iWriteDataDelay & 0x0f);mLength -= 3;}}}if (iReadLength) {mLength = mCH341_PACKET_LENGTH - i % mCH341_PACKET_LENGTH; // 当前包剩余长度,<mCH341A_CMD_I2C_STM_MAXif (mLength <= 3) {while (mLength--)mWrBuf[i++] = mCH341A_CMD_I2C_STM_END; // 当前包提前结束mLength = mCH341_PACKET_LENGTH;}if (mLength >= mCH341_PACKET_LENGTH)mWrBuf[i++] = mCH341A_CMD_I2C_STREAM; // 新包的命令码mWrBuf[i++] = mCH341A_CMD_I2C_STM_US | (iAddrDelay1 & 0x0f);if (iWriteLength > 1) {                                 // 先输出mWrBuf[i++] = mCH341A_CMD_I2C_STM_STA;              // 产生起始位mWrBuf[i++] = (UCHAR)(mCH341A_CMD_I2C_STM_OUT | 1); // 输出数据,位5-位0为长度mWrBuf[i++] = *(PUCHAR)iWriteBuffer | 0x01;         // I2C目标设备地址,最低位为1则进行读操作} else if (iWriteLength) {                              // 输出一字节后直接输入i--;mWrBuf[i++] = *(PUCHAR)iWriteBuffer | 0x01; // I2C目标设备地址,最低位为1则进行读操作}mWrBuf[i++] = mCH341A_CMD_I2C_STM_US | (iAddrDelay2 & 0x0f); // 延时10微秒for (j = 1; j < iReadLength;) {mLength = mCH341_PACKET_LENGTH - i % mCH341_PACKET_LENGTH; // 当前包剩余长度,<mCH341A_CMD_I2C_STM_MAXif (mLength <= 1) {if (mLength)mWrBuf[i++] = mCH341A_CMD_I2C_STM_END; // 当前包提前结束mLength = mCH341_PACKET_LENGTH;}if (mLength >= mCH341_PACKET_LENGTH)mWrBuf[i++] = mCH341A_CMD_I2C_STREAM; // 新包的命令码mLength = iReadLength - j >= mCH341A_CMD_I2C_STM_MAX ? mCH341A_CMD_I2C_STM_MAX : 1; // 本次输入有效数据长度mWrBuf[i++] = (UCHAR)(mCH341A_CMD_I2C_STM_IN | mLength);                            // 输入数据,位5-位0为长度j += mLength;if (mLength >= mCH341A_CMD_I2C_STM_MAX) {                 // 当前包将满mWrBuf[i] = mCH341A_CMD_I2C_STM_END;                  // 当前包提前结束i += mCH341_PACKET_LENGTH - i % mCH341_PACKET_LENGTH; // 跳过当前包剩余部分}mWrBuf[i++] = mCH341A_CMD_I2C_STM_US | (iReadDataDelay & 0x0f); // 延时10微秒}mLength = mCH341_PACKET_LENGTH - i % mCH341_PACKET_LENGTH; // 当前包剩余长度,<mCH341A_CMD_I2C_STM_MAXif (mLength <= 1) {if (mLength)mWrBuf[i++] = mCH341A_CMD_I2C_STM_END; // 当前包提前结束mLength = mCH341_PACKET_LENGTH;}if (mLength >= mCH341_PACKET_LENGTH)mWrBuf[i++] = mCH341A_CMD_I2C_STREAM; // 新包的命令码mWrBuf[i++] = mCH341A_CMD_I2C_STM_IN;     // 输入数据,只接收一个字节并发送无应答}mLength = mCH341_PACKET_LENGTH - i % mCH341_PACKET_LENGTH; // 当前包剩余长度,<mCH341A_CMD_I2C_STM_MAXif (mLength <= 1) {if (mLength)mWrBuf[i++] = mCH341A_CMD_I2C_STM_END; // 当前包提前结束mLength = mCH341_PACKET_LENGTH;}if (mLength >= mCH341_PACKET_LENGTH)mWrBuf[i++] = mCH341A_CMD_I2C_STREAM; // 新包的命令码mWrBuf[i++] = mCH341A_CMD_I2C_STM_STO;    // 产生停止位mWrBuf[i++] = mCH341A_CMD_I2C_STM_END;    // 当前包提前结束mLength = 0;if (iReadLength)j = CH341WriteRead(iIndex, i, mWrBuf, mCH341A_CMD_I2C_STM_MAX, (iReadLength + mCH341A_CMD_I2C_STM_MAX - 1) / mCH341A_CMD_I2C_STM_MAX, &mLength, oReadBuffer); // 执行数据流命令,先输出再输入elsej = CH341WriteData(iIndex, mWrBuf, &i); // 写出数据块if (j && mLength != iReadLength)j = FALSE;if (mWrBuf != mBuffer)LocalFree(mWrBuf); // 如果是分配的内存则释放return (j);
}

演示示意图，红色部分为作用间隔时间。