DS18B20程序流程图
我们根据上面流程图采用单总线库：OneWire完成程序编写
#include <OneWire.h>
OneWire ds(12）; // 连接arduino12引脚
void setup(void)
{
Serial.begin(9600);
}
void loop(void)
{
byte i;
byte present = 0;
byte type_s;
byte data[12];
byte addr[8];
float celsius, fahrenheit;
if ( !ds.search(addr))
{
Serial.println("No more addresses.");
Serial.println();
ds.reset_search();
delay(250);
return;
}
Serial.print("ROM =");
for( i = 0; i < 8; i )
{
Serial.write(' ');
Serial.print(addr, HEX);
}
if (OneWire::crc8(addr, 7) != addr[7])
{
Serial.println("CRC is not valid!");
return;
}
Serial.println();
// the first ROM byte indicates which chip
switch (addr[0])
{
case 0x10:
Serial.println(" Chip = DS18S20"); // or old DS1820
type_s = 1;
break;
case 0x28:
Serial.println(" Chip = DS18B20");
type_s = 0;
break;
case 0x22:
Serial.println(" Chip = DS1822");
type_s = 0;
break;
default:
Serial.println("Device is not a DS18x20 family device.");
return;
}
ds.reset();
ds.select(addr);
ds.write(0x44,1); // start conversion, with parasite power on at the end
delay(1000); // maybe 750ms is enough, maybe not
// we might do a ds.depower() here, but the reset will take care of it.
present = ds.reset();
ds.select(addr);
ds.write(0xBE); // Read Scratchpad
Serial.print(" Data = ");
Serial.print(present,HEX);
Serial.print(" ");
for ( i = 0; i < 9; i ) { // we need 9 bytes
data = ds.read();
Serial.print(data, HEX);
Serial.print(" ");
}
Serial.print(" CRC=");
Serial.print(OneWire::crc8(data, 8), HEX);
Serial.println();
// convert the data to actual temperature
unsigned int raw = (data[1] << 8) | data[0];
if (type_s) {
raw = raw << 3; // 9 bit resolution default
if (data[7] == 0x10) {
// count remain gives full 12 bit resolution
raw = (raw & 0xFFF0) 12 - data[6];
}
} else {
byte cfg = (data[4] & 0x60);
if (cfg == 0x00) raw = raw << 3; // 9 bit resolution, 93.75 ms
else if (cfg == 0x20) raw = raw << 2; // 10 bit res, 187.5 ms
else if (cfg == 0x40) raw = raw << 1; // 11 bit res, 375 ms
// default is 12 bit resolution, 750 ms conversion time
}
celsius = (float)raw / 16.0;
fahrenheit = celsius * 1.8 32.0;
Serial.print(" Temperature = ");
Serial.print(celsius);
Serial.print(" Celsius, ");
Serial.print(fahrenheit);
Serial.println(" Fahrenheit");
}
程序还是蛮复杂的，不过我们有更简单的办法：使用DS18B20程序库：DallasTemperature。
#include <OneWire.h>
#include <DallasTemperature.h>
// 定义DS18B20数据口连接arduino的12号IO上
#define ONE_WIRE_BUS 12
// 初始连接在单总线上的单总线设备
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);
void setup(void)
{
// 设置串口通信波特率
Serial.begin(9600);
Serial.println("Dallas Temperature IC Control Library Demo");
// 初始库
sensors.begin();
}
void loop(void)
{
Serial.print("Requesting temperatures...");
sensors.requestTemperatures(); // 发送命令获取温度
Serial.println("DONE");
Serial.print("Temperature for the device 1 (index 0) is: ");
Serial.println(sensors.getTempCByIndex(0));
}
这样是不是简单多了呢，你可以接上数码管，液晶屏等显示设备，就完成一个温度计的制作了。
