BQ27742-G1读取电池电压问题咨询
BQ27742-G1，用EV2300读取电池电压正确，参照TI给的参考例程用STM32的模拟IIC读取电池电压信息，反复测试就是不能读到正确的电池电压信息，以下是我的设计代码，请大神帮看下时序有问题还是？万分感谢！
#define I2CSLAVEADDR 0x55 // 7-bit slave address
unsigned char RxData[2]; // Stores data bytes that are RX'd
void IIC_Init(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE );
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6|GPIO_Pin_7;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP ; //推挽输出
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; //输出最高速率50MHz
GPIO_Init(GPIOB, &GPIO_InitStructure);
GPIO_SetBits(GPIOB,GPIO_Pin_6|GPIO_Pin_7); //PB6,PB7输出高
}
//产生IIC起始信号
void IIC_Start(void)
{
SDA_OUT(); //sda线输出
IIC_SDA=1;
delay_us(1);
IIC_SCL=1;
delay_us(6);
IIC_SDA=0;//START:when CLK is high,DATA change form high to low
delay_us(6);
IIC_SCL=0;//钳住I2C总线，准备发送或接收数据
delay_us(2);
}
//产生IIC停止信号
void IIC_Stop(void)
{
SDA_OUT();//sda线输出
//IIC_SCL=0;
//delay_us(2);
IIC_SDA=0;//STOP:when CLK is high DATA change form low to high
delay_us(2);
IIC_SCL=1;
delay_us(6);
IIC_SDA=1;//发送I2C总线结束信号
delay_us(4);
}
//等待应答信号到来
//返回值：1，接收应答失败
// 0，接收应答成功
u8 IIC_Wait_Ack(void)
{
u8 ucErrTime=0;
SDA_IN(); //SDA设置为输入
IIC_SDA=1;delay_us(2);
IIC_SCL=1;delay_us(2);
while(READ_SDA)
{
ucErrTime++;
if(ucErrTime>250)
{
IIC_Stop();
return 1;
}
}
IIC_SCL=0;//时钟输出0
return 0;
}
//主机产生ACK应答
void IIC_Ack(void)
{
IIC_SCL=0;
SDA_OUT();
IIC_SDA=0;
delay_us(2);
IIC_SCL=1;
delay_us(2);
IIC_SCL=0;
}
//不产生ACK应答
void IIC_NAck(void)
{
IIC_SCL=0;
SDA_OUT();
IIC_SDA=1;
delay_us(2);
IIC_SCL=1;
delay_us(2);
IIC_SCL=0;
}
//IIC发送一个字节
//返回从机有无应答
//1，有应答
//0，无应答
void IIC_Send_Byte(u8 txd)
{
u8 t;
SDA_OUT();
IIC_SCL=0;//拉低时钟开始数据传输
for(t=0;t<8;t++)
{
IIC_SDA=(txd&0x80)>>7;
txd<<=1;
delay_us(10);
IIC_SCL=1;
delay_us(10);
IIC_SCL=0;
delay_us(10);
}
}
//读1个字节，ack=1时，发送ACK，ack=0，发送nACK
u8 IIC_Read_Byte(unsigned char ack)
{
unsigned char i,receive=0;
SDA_IN();//SDA设置为输入
for(i=0;i<8;i++ )
{
IIC_SCL=0;
delay_us(10);
IIC_SCL=1;
receive<<=1;
if(READ_SDA)receive++;
delay_us(10);
}
IIC_SCL = 0;
if (!ack)
IIC_NAck();//发送nACK
else
IIC_Ack(); //发送ACK
return receive;
}
void I2C_27742_writeBlock(unsigned char SlaveAddress,
unsigned int numBytes, unsigned char multi,
void* TxData)
{
unsigned int i;
unsigned char *temp;
temp = (unsigned char *)TxData;
IIC_Start();
IIC_Send_Byte((SlaveAddress << 1) & 0xFE);
S1=IIC_Wait_Ack();
for (i = 0; i < numBytes; i++)
{
IIC_Send_Byte(*(temp)); // Send data and ack
S2=IIC_Wait_Ack();
temp++; // Increment pointer to next element
}
if (multi == 0) // Need STOP condition?
{
IIC_Stop(); // Yes, send STOP condition
}
}
void I2C_27742_readBlock(unsigned char SlaveAddress,
unsigned int numBytes, void* RxData)
{
unsigned int i;
unsigned char* temp;
temp = (unsigned char *)RxData; // Initialize array pointer
IIC_Start();
IIC_Send_Byte((SlaveAddress << 1) & 0xFE);
S3=IIC_Wait_Ack();
IIC_Start(); // Send Start condition
IIC_Send_Byte((SlaveAddress << 1) | 0x01); // [ADDR] + R/W bit = 1
S4=IIC_Wait_Ack();
for (i = 0; i < numBytes; i++)
{
if (i == (numBytes - 1))
*(temp) = IIC_Read_Byte(0);// Read last 8-bit data with no ACK
else
*(temp) = IIC_Read_Byte(1);// Read 8-bit data & then send ACK
temp++; // Increment pointer to next element
}
IIC_Stop(); // Send Stop condition
}
void bq27742_read(unsigned char cmd, unsigned int bytes)
{
unsigned char tx[1];
tx[0] = cmd;
I2C_27742_writeBlock(I2CSLAVEADDR, 1, 1, tx);
I2C_27742_readBlock(I2CSLAVEADDR, bytes,RxData);
}
unsigned int transBytes2UnsignedInt(unsigned char msb, unsigned char lsb)
{
unsigned int tmp;
tmp = ((msb << 8) & 0xFF00);
return ((unsigned int)(tmp + lsb) & 0x0000FFFF);
}
int main(void)
{
SysInit(); //初始化
while(1)//--------------------------------------------------------------------------------------------------------------------------------
{
bq27742_read(0x08, 2);
C1 = transBytes2UnsignedInt(RxData[1], RxData[0]);
}
}
可能直接抓个I2C通讯的波形发上来更加直观
上图是我抓取的波形图，还请协助分析下，谢谢！
你的I2C波形有点问题。
首先start后，你是要发送0xFF吗？因为第一byte的SDA都是高电平，其次在第8个clock后，有异常的脉冲。