[STM32F042 NucLeo] Mbed+DHT11温湿度

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leo121_3006061 提问时间：2016-12-5 12:17 /

正好手头上有个DHT11温湿度传感器,在Mbed下初步试着用了一下,代码相当简单

include "mbed.h"
//------------------------------------
// Hyperterminal configuration
// 115200 bauds, 8-bit data, no parity
//------------------------------------
Serial pc(SERIAL_TX, SERIAL_RX);
DigitalOut myled(LED1);
DigitalInOut data_pin(A0); // Activate digital in as dht11 Pin
Timer tmr; //initialize timer
uint64_t adat; // 64 bit variable for temporary data
int i;
void dht_read(void) {
data_pin.output(); // Set A0 as output
// Initialize measurement > 18 ms low
data_pin = 0;
wait_ms(20);
// After high and release the pin switch input mode
data_pin = 1;
data_pin.input();
// Wait until the end of 80 us low
while(!data_pin.read()) {}
// Wait until end of 80 us high
while(data_pin.read()) {}
// 40 bit, 40 read out cycle
for(i=0; i<40; i++) {
adat = adat << 1; // Shift for new number
tmr.stop(); // Stop timer if runs
tmr.reset(); // Reset timer
// Wait until pin
while(!data_pin.read()) {}
tmr.start();
while(data_pin.read()) {}
// If DHT11 HIGH longer than 40 micro seconds (hopefully 70 us)
if(tmr.read_us() > 40) {
// bit is 1
adat++;
}
}
}
int main() {
pc.printf("Hello World !\r\n");
pc.baud(115200);
pc.printf("Read the DHT11 temperature and humidity sensor!\r\n"); //Welcome message
while(1) {
adat = 0;
myled = !myled; // LED is ON/OFF
dht_read(); // Call the function
// Send result through UART result
pc.printf("Humidity: ");
pc.printf("%d", (adat & 0x000000ff00000000) >> 32); // Humidity
pc.printf("\n\r"); // Send a new line and carriage return.
pc.printf("Temperature: ");
pc.printf("%d", (adat & 0x0000000000ff0000) >> 16 ); // Temperature
pc.printf("\n\r");
pc.printf("Checksum: ");
pc.printf("%d", adat & 0x00000000000000ff); // Checksum.
pc.printf("\n\r");
wait(2); // Wait 2 sec till continue.
}
}