Files
file	dht11-sensor.c
	DHT 11 sensor implementation.

file	dht11-sensor.h
	DHT 11 sensor header file.

Macros
#define	DHT11_SIGNAL_HIGH (1)
	GPIO High.

#define	DHT11_SIGNAL_LOW (0)
	GPIO Low.

#define	DHT11_SIGNAL_START_PHASE1_DURATION (40)
	Duration of signal start phase 1 according to data sheet.

#define	DHT11_SIGNAL_START_PHASE2_DURATION (80)
	Duration of signal start phase 2 according to data sheet.

#define	DHT11_SIGNAL_START_PHASE3_DURATION (80)
	Duration of signal start phase 3 according to data sheet.

#define	DHT11_SIGNAL_RESPONSE_PHASE1_DURATION (50)
	Duration of signal response phase 1 according to data sheet.

#define	DHT11_SIGNAL_RESPONSE_BIT_0_DURATION (28)
	Duration of signal response if bit is set to 0, according to data sheet.

#define	DHT11_SIGNAL_RESPONSE_BIT_1_DURATION (70)
	Duration of signal response if bit is set to 1, according to data sheet.

#define	DHT11_TICKS_GUARD (1)
	Sensor timer drift in ticks.

#define	DHT11_US_GUARD RTIMERTICKS_TO_US(1)
	Sensor timer drift in us from rtimer.

#define	DHT11_DATA_SAMPLES (40)
	Number of data requests.

#define	DHT11_DATA_SIZE (5)
	Number of bytes in data.

#define	DHT11_SAMPLING_RATE_SECONDS (1)
	DHT11 maximum sample rate is 1 Hz (1 second)

#define	DHT11_CONFIGURE_GPIO_PORT (0)
	DHT11 Configuration type for GPIO Port.

#define	DHT11_CONFIGURE_GPIO_PIN (1)
	DHT11 Configuration type for GPIO Pin.

#define	DHT11_VALUE_HUMIDITY_INTEGER (0)
	DHT11 value type for humidity integer part.

#define	DHT11_VALUE_HUMIDITY_DECIMAL (1)
	DHT11 value type for humidity decimal part.

#define	DHT11_VALUE_TEMPERATURE_INTEGER (2)
	DHT11 value type for temperature integer part.

#define	DHT11_VALUE_TEMPERATURE_DECIMAL (3)
	DHT11 value type for temperature decimal part.

#define	DHT11_STATUS_OKAY (0)
	DHT11 status okay.

#define	DHT11_STATUS_TIMEOUT (1)
	DHT11 status timeout.

#define	DHT11_STATUS_CHECKSUM_FAILED (2)
	DHT11 status checksum failed.

Functions
static uint8_t	dht_read (void)

Variables
static dht_t	dht
	DHT struct.

Detailed Description

Macro Definition Documentation

◆ DHT11_TICKS_GUARD

#define DHT11_TICKS_GUARD (1)

Sensor timer drift in ticks.

DHT uses 1us granularity and rtimer granularity is higher. So, allow the reading to drift by 1 tick

Definition at line 106 of file dht11-sensor.c.

◆ DHT11_US_GUARD

#define DHT11_US_GUARD RTIMERTICKS_TO_US(1)

Sensor timer drift in us from rtimer.

DHT uses 1us granularity and rtimer granularity is higher. So, allow the reading to drift by 1 tick in us

Definition at line 115 of file dht11-sensor.c.

Referenced by dht_read().

Function Documentation

◆ dht_read()

static uint8_t dht_read ( void )

static

Data Single-bus free status is at high voltage level. When the communication between MCU and DHT11 begins, the programme of MCU will set Data Single-bus voltage level from high to low and this process must take at least 18ms to ensure DHT’s detection of MCU's signal, then MCU will pull up voltage and wait 20-40us for DHT’s response.

Once DHT detects the start signal,it will send out a low-voltage-level response signal, which lasts 80us. Then the programme of DHT sets Data Single-bus voltage level from low to high and keeps it for 80us for DHT’s preparation for sending data.

When DHT is sending data to MCU, every bit of data begins with the 50us low-voltage-level and the length of the following high-voltage-level signal determines whether data bit is "0" or "1"

26-28us voltage-length means data "0" 70us voltage-length means 1 bit data "1"

Definition at line 229 of file dht11-sensor.c.

References dht, DHT11_DATA_SAMPLES, DHT11_DATA_SIZE, DHT11_SIGNAL_HIGH, DHT11_SIGNAL_LOW, DHT11_SIGNAL_RESPONSE_BIT_0_DURATION, DHT11_SIGNAL_RESPONSE_BIT_1_DURATION, DHT11_SIGNAL_RESPONSE_PHASE1_DURATION, DHT11_SIGNAL_START_PHASE1_DURATION, DHT11_SIGNAL_START_PHASE2_DURATION, DHT11_SIGNAL_START_PHASE3_DURATION, DHT11_STATUS_CHECKSUM_FAILED, DHT11_STATUS_OKAY, DHT11_STATUS_TIMEOUT, DHT11_US_GUARD, and RTIMER_BUSYWAIT.

Files

Macros