分享使用串口操作DS18B20的代码，简化时序，提高系统实时

dmf1988

硬件连接： DS18B20连接到STM32F407VE的PA0， PA0是UART4接口的TX脚， 也是该串口单线半双工模式下时的TXRX脚，可以用此单引脚来发送和接收。该脚外接上拉电阻。

用硬件操作的好处是全程不需要禁止中断，另外还可以用串口中断方式或DMA来操作

下面上代码：

[/table]

static const unsigned char crc_tab[256]={

0, 94,188,226, 97, 63,221,131,194,156,126, 32,163,253, 31, 65,

157,195, 33,127,252,162, 64, 30, 95,  1,227,189, 62, 96,130,220,

35,125,159,193, 66, 28,254,160,225,191, 93,  3,128,222, 60, 98,

190,224,  2, 92,223,129, 99, 61,124, 34,192,158, 29, 67,161,255,

70, 24,250,164, 39,121,155,197,132,218, 56,102,229,187, 89,  7,

219,133,103, 57,186,228,  6, 88, 25, 71,165,251,120, 38,196,154,

101, 59,217,135,  4, 90,184,230,167,249, 27, 69,198,152,122, 36,

248,166, 68, 26,153,199, 37,123, 58,100,134,216, 91,  5,231,185,

140,210, 48,110,237,179, 81, 15, 78, 16,242,172, 47,113,147,205,

17, 79,173,243,112, 46,204,146,211,141,111, 49,178,236, 14, 80,

175,241, 19, 77,206,144,114, 44,109, 51,209,143, 12, 82,176,238,

50,108,142,208, 83, 13,239,177,240,174, 76, 18,145,207, 45,115,

202,148,118, 40,171,245, 23, 73,  8, 86,180,234,105, 55,213,139,

87,  9,235,181, 54,104,138,212,149,203, 41,119,244,170, 72, 22,

233,183, 85, 11,136,214, 52,106, 43,117,151,201, 74, 20,246,168,

116, 42,200,150, 21, 75,169,247,182,232, 10, 84,215,137,107, 53

};

unsigned char Check_crc8(unsigned char *p,unsigned char n)

{

unsigned char i,crc8=0;

for(i=0;i<n;i++)

crc8=crc_tab[crc8^p];                //连续查表计算CRC

return crc8;

}

void DS18B20Init()

{

//时钟，UART4, PA0

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA,ENABLE);

RCC_APB1PeriphClockCmd(RCC_APB1Periph_UART4,ENABLE);

//GPIO-&gtA0

GPIO_InitTypeDef Gpio = {GPIO_Pin_0,GPIO_Mode_AF,GPIO_Low_Speed,GPIO_OType_OD,GPIO_PuPd_NOPULL};

GPIO_Init(GPIOA,&Gpio);

GPIO_PinAFConfig(GPIOA,GPIO_PinSource0,GPIO_AF_UART4);

//UART4

USART_InitTypeDef Uart = {        115200,

USART_WordLength_8b,

USART_StopBits_1,

USART_Parity_No,

USART_Mode_Rx USART_Mode_Tx,

USART_HardwareFlowControl_None};

USART_Init(UART4,&Uart);

USART_HalfDuplexCmd(UART4,ENABLE);

USART_Cmd(UART4,ENABLE);

//

}

bool DS18B20Reset()

{

u8 rx;

UART4->BRR = 0x1117;                        //9600

UART4->DR = 0xF0;

while (!(UART4->SR&USART_SR_RXNE));

rx = UART4->DR;

UART4->BRR = 0x16C;                                //115200

return rx!=0xF0;

}

void DS18B20WriteByte(u8 byte)

{

for (int i=0;i<8;i++)

{

u8 c=(byte&0x01) ? 0xff:0x00;

UART4->DR = c;

byte>>=1;

while (!(UART4->SR&USART_SR_RXNE));

c=UART4->DR;

}

}

u8 DS18B20ReadByte()

{

u8 byte,rx;

for (int i=0;i<8;i++)

{

UART4->DR = 0xff;

byte>>=1;

while (!(UART4->SR&USART_SR_RXNE));

rx=UART4->DR;

if (rx==0xff) byte =0x80;

}

return byte;

}

int DS18B20GetTemp()

{

u8 Buf[9];

//发送复位信号

if (!DS18B20Reset()) return -1;

//发送SKIP_ROM

DS18B20WriteByte(0xCC);

//发送转换温度命令

DS18B20WriteByte(0x44);

//等待转换, 最大750ms

OSTimeDly(800);

//发送复位信号

if (!DS18B20Reset()) return -1;

//发送SKIP_ROM

DS18B20WriteByte(0xCC);

//发送读取温度命令

DS18B20WriteByte(0xBE);

//读取9字节内存

for (int i=0;i<9;i++)

Buf=DS18B20ReadByte();

//CRC

if (Check_crc8(Buf,9)!=0)

return -1;

return Buf[1]*256+Buf[0];

}

[table=100%,#ffffff]附件为全部软件代码

STM32F407_DS18B20.rar (12.35 MB, 下载次数: 3) 2018-1-12 22:13 上传 点击文件名下载附件

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