通过串行通讯,当主机向传感器发送请求时,输出口变输入口,向主机传送1byte数据。传送完毕后,输出口变输入口,再次等待主机发送请求。
读取 DHT11 温湿度传感器的值,然后发送给 PC 通过串口显示出来。
int DHpin = 2; byte dat[5]; byte read_data() { byte data; for(int i=0; i<8; i++) { if(digitalRead(DHpin) == LOW) { while(digitalRead(DHpin) == LOW); //等待50us; delayMicroseconds(30); //判断高电平的持续时间,以判定数据是‘0’还是‘1’; if(digitalRead(DHpin) == HIGH) data |= (1<<(7-i)); //高位在前,低位在后; while(digitalRead(DHpin) == HIGH); //数据‘1’,等待下一位的接收; } } return data; } void start_test() { digitalWrite(DHpin,LOW); //拉低总线,发开始信号; delay(30); //延时要大于18ms,以便DHT11 能检测到开始信号; digitalWrite(DHpin,HIGH); delayMicroseconds(40); //等待DHT11 响应; pinMode(DHpin,INPUT); while(digitalRead(DHpin) == HIGH); delayMicroseconds(80); //DHT11 发出响应,拉低总线80us; if(digitalRead(DHpin) == LOW); delayMicroseconds(80); //DHT11 拉高总线80us 后开始发送数据; for(int i=0;i<4;i++) //接收温湿度数据,校验位不考虑; dat[i] = read_data(); pinMode(DHpin,OUTPUT); digitalWrite(DHpin,HIGH); //发送完一次数据后释放总线,等待主机的下一次始信号; } void setup() { Serial.begin(9600); pinMode(DHpin,OUTPUT); } void loop() { start_test(); Serial.print("Current humdity = "); Serial.print(dat[0], DEC); //显示湿度的整数位; Serial.print('.'); Serial.print(dat[1],DEC); //显示湿度的小数位; Serial.println('%'); Serial.print("Current temperature = "); Serial.print(dat[2], DEC); //显示温度的整数位; Serial.print('.'); Serial.print(dat[3],DEC); //显示温度的小数位; Serial.println('C'); delay(700); }