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STM32 DHT11, DHT22 & DS18B20 with Timer‑Based Microsecond Delay (HAL + CubeMX)
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Mar 5, 2020
Learn how to interface DHT11, DHT22, and DS18B20 temperature/humidity sensors with an STM32 microcontroller, using precise microsecond delay via timer configured in STM32CubeMX and coding with HAL drivers. This tutorial demonstrates wiring, one-wire timing, sensor initialization, and reading of digital data from three popular sensors. Use of timer-based delay routines ensures accurate timing according to sensor datasheets. Perfect for embedded developers building environmental sensing projects on STM32. 🔧 Highlights: • Generating micro‑delay with TIM timers for reliable sensor communication • Reset/init sequence and data read for DHT11, DHT22, DS18B20 • Displaying temperature and humidity results (shown on UART or I2C LCD) • Works on Blue Pill, Nucleo, STM32F1/F4 families 📁 Read the full tutorial with code: 👉 https://controllerstech.com/using-dht11-sensor-with-stm32/ 👉 https://controllerstech.com/temperature-measurement-using-dht22-in-stm32/ 👉 https://controllerstech.com/ds18b20-and-stm32/ 📌 Subscribe for more STM32 sensor tutorials! #STM32 #DHT11 #DS18B20 #DHT22 #TimerDelay #CubeMX #EmbeddedSystems ________________________________________________________________________________________ ******* SUPPORT US BY DONATING******
View Video Transcript
0:07
hello everyone welcome to controllers
0:11
tech today in this video I am going to
0:15
show you how to work with the
0:16
temperature sensors that only uses one
0:19
wire to communicate in this video I will
0:23
cover two HD 11-day HD 22 and ds1 8b
0:27
$0.20 errs the first part of the video
0:30
will be common to all three sensors as I
0:33
am going to use the same pin for all
0:35
three of them let's start by creating a
0:39
project in stm32 cube ide i am using
0:44
stm32f4 for 6r ii controller give the
0:51
name to the project and click finish
0:58
in the cube MX first of all I am setting
1:01
external crystal for the clock I am
1:10
using timer six for creating delay in
1:12
microseconds pin pa1 will be the data
1:17
pin for the sensors and i2c is for
1:24
connecting the LCD 1602 let's set the
1:35
clock now I have eight megahertz
1:38
oscillator on board
1:40
I want the controller to run at fifty
1:43
megahertz
1:53
[Music]
1:55
8pv one clock is also running at 50
1:58
megahertz and that's where my timer 6 is
2:01
connected
2:02
I chose low frequency for the HCL K
2:06
because some of you complained that the
2:08
microsecond delay is not working at
2:10
lower frequencies I am setting timer to
2:16
create delay in microseconds if you
2:19
don't understand it check out the video
2:21
of the top right corner click Save to
2:24
generate the project
2:31
I am including i2c LCD related files in
2:40
the project
3:00
if you are not using stm32f4 you need to
3:05
change it accordingly if you are using
3:14
any other eye to see change it here I
3:23
will build this code once to check for
3:26
any errors
3:38
this is 4s print f function we need to
3:50
write some functions first delay is to
3:54
create delay in microseconds basically
3:58
set the counter to zero and then wait
4:01
for the counter to reach the entered
4:02
value these are some variables that we
4:13
are going to use throughout these are
4:16
functions to set the pin as input or
4:18
output based on the requirement you can
4:27
change to pull up or no pull if you are
4:30
not getting the data from the pin
4:46
now the DHD 11 specific cart starts
4:50
let's take a look at the datasheet
4:53
this is the overall communication of the
4:56
sensor
5:02
it starts with sending a start signal to
5:06
the day HD 11 MCU sends the start signal
5:10
by pulling the line low for 18
5:12
milliseconds and then high for 20 to 40
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microseconds
5:20
[Music]
5:27
I am defining the pin and the port for
5:31
the dht11 sensor this is the function to
5:39
send the start signal first the MCU
5:46
we'll pull the pin low and then keep it
5:49
low for 18 milliseconds then MCU will
5:53
pull the pin high and keep it high for
5:55
20 to 40 micro seconds after that MCU
6:03
will release the pin after receiving the
6:09
start signal dht11 will send a response
6:12
to the MCU to do so it will pull the
6:18
line low for 80 micro seconds and then
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high for 80 micro seconds this is the
6:29
function to check response we first wait
6:33
for 40 microseconds that means we are
6:39
here on the timeline then we check for
6:42
the pin to be low which is actually low
6:45
so we will wait for eighty microseconds
6:52
basically we reach here on the timeline
6:55
now we will check if the pin is high if
6:59
it is that means the sensor is present
7:02
or else the sensor is not present
7:12
finally we will wait for the pin to go
7:14
low again
7:24
now after transmitting the response the
7:27
dht11 will start transmitting data
7:30
before transmitting any bit
7:33
it keeps the line low for 50
7:35
microseconds which is followed by a high
7:38
for 26 to 28 microseconds if the bit is
7:42
a zero or a high for 70 microseconds if
7:45
the bit is a one
7:54
this is the function to read the data
7:56
from dht11 first we will wait for the
8:00
pin to go high which means we will be
8:07
here on the time line
8:15
now we will wait for 40 microseconds if
8:25
a zero was received we will be here on
8:27
the timeline and the pin would be low at
8:30
this point or if a one was received we
8:34
will be here and the pin would be high
8:37
based on the result we store the data at
8:40
the respective position let's start by
8:48
starting the timer first initialize the
8:52
LCD i am sending this string to the LCD
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wait for some time clear the display
9:10
now start the day HD 11 record the
9:14
response from the sensor sensor will
9:24
send 40 bits of data which includes
9:26
integral RH data decimal RH data
9:30
integral temperature data decimal
9:32
temperature data and the checksum so we
9:36
will read 5 bytes of this data
9:43
temperature data is from the integral
9:46
part and Rh data is also from the
9:49
integral part
9:59
also these are the functions to display
10:02
the temperature and humidity data on the
10:05
LCD
10:16
I am writing display functions in the
10:19
beginning so that they can be common to
10:21
all other sensors also
10:57
and in the end give some delay
11:01
[Music]
11:02
you
11:10
there is the floating point error
11:12
because I am trying to convert the float
11:14
into character go to project setting C++
11:22
build setting tool setting and select
11:25
you printf float
11:29
[Music]
11:41
the project builds successfully let's
11:45
debug the code
11:56
let's see the result on the LCD itself
11:59
you can see the data being displayed on
12:02
the LCD
12:06
[Music]
12:23
notice the increase in temperature when
12:26
I am touching the sensor this is it for
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the day HT 11 the next part of this
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video will cover the day HD 22 when than
12:37
dsb 1 8 b 20 you can download the code
12:41
from the link in the description
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[Music]
12:54
first we need to define the pin for the
12:57
day HD 22
13:07
eh t20 to start sends the start signal
13:11
to the sensor let's take a look at the
13:14
dht22 datasheet to transmit a start
13:18
signal the MCU needs to pull the data
13:21
line low for at least one milliseconds
13:23
and then it needs to pull the line high
13:26
for around twenty to forty microseconds
13:29
the pin must be released after that on
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receiving start signal sensor we'll send
13:48
the response it will pull the line low
13:55
for eighty microseconds and then high
13:57
for another eighty microseconds now we
14:12
will first wait for 40 microseconds
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which means that we are here on the time
14:17
line and the pin should read low here
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if it does we will wait for another 80
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microseconds that brings us here on the
14:35
timeline the pin should read high here
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and that indicate the sensors presence
14:51
after that we will wait for the pin to
14:54
go low
14:54
[Music]
15:03
to transmit data dht22 will pull the
15:08
line low for 50 microseconds followed by
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pulling it high for 26 to 28
15:12
microseconds in case the bit is zero to
15:21
transmit a one day HT 22 will pull the
15:24
line low for 50 microseconds followed by
15:27
pulling it high for 70 microseconds to
15:42
read the data we will wait for the pin
15:44
to go high this brings us here on the
15:51
time line
15:52
[Music]
16:00
[Music]
16:02
we will wait for 40 microseconds then if
16:12
the bit was a zero we would be here
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after 40 microseconds and the pin would
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read low if the bit was a 1 we would be
16:22
here and the pin would be high we will
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record the bit at the respective
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position and wait for the pin to go low
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before reading next bit
16:52
[Music]
16:54
inside the main function first start the
16:57
timer initialize the LCD i am sending
17:02
this string to the display wait for some
17:06
time and clear the display here are the
17:09
functions to display the temperature and
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humidity on the LCD first of all send
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the start signal to the sensor read the
17:29
response from the sensor sensor will
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send 40 bits of data which includes
17:35
integral RH data decimal RH data
17:38
integral temperature data decimal
17:41
temperature data and the checksum so we
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will read 5 bytes of this data
17:58
now we will combine the integral and
18:01
decimal part of the data finally convert
18:05
the values to the proper float
18:18
you
18:25
let's build and debug
18:42
as you can see here the values of
18:45
temperature and humidity are being
18:48
displayed this is it for the day HD 22
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sensor the next part of this video is
18:55
about ds1 8b 20 the code from the link
19:00
in the description here is the function
19:04
to create delay in microseconds these
19:08
functions are used to display
19:10
temperature and humidity values on the
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LCD functions to set the pin as output
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or input
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first of all I am defining the data pin
19:39
for the ds1 8b 28 is connected to pin
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pa1 start function is to send the start
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signal to the sensor it start by setting
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the pin in this output pull the pin low
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and hold it low for 480 microseconds as
20:10
you can see in the datasheet the master
20:14
have to pull the data line low for 480
20:17
microseconds after that we will release
20:21
the pin by setting it as input
20:31
on receiving the start signal sensor
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will send the response to indicate its
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presence so we will wait for eighty
20:40
microseconds we should be here on the
20:49
time line now we will read the pin if
20:53
the pin is low the sensor is present as
20:56
it's the one which pulled the line low
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now we will wait another 400 seconds to
21:02
complete the response cycle
21:14
this will complete the initialization of
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the sensor
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next is the right function to write data
21:35
to the sensor to write a one we must
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first set the pin as output then pull
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the pins low and hold it low for 1
21:46
microseconds you can see that here after
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1 microseconds we must release the pin
22:00
by setting it as input and wait for
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around 60 microseconds for this cycle to
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get over
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to write a zero we have to again set the
22:29
pin in his output then pull the pins low
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and hold it low for around 60 micro
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seconds and finally release the pin by
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setting it as input re function reads
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the data from the sensor to read the
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data we must set the pin as output first
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pull the pin low and hold it low for 2
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microseconds now we will set the pin as
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input and read the data pin the
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microcontroller is going to sample the
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data here and if the pin would be high
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which means that we are here on the time
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line and the data read would be a 1 if
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the pin would be low the data read must
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be a zero and at last we have to wait
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for 60 microseconds for the cycle to get
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over
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[Music]
23:49
inside the main function first start the
23:52
timer initialize the LCD display some
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string on the LCD wait for some time and
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clear the display now inside the while
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loop let's take an example from the
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datasheet
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[Music]
24:22
first send the start signal and look for
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the presence of the sensor next write
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the skip ROM command and write scratch
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pad with convert temperature command
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again send the start read the response
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and skip ROM command and read scratch
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pad command
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read the nine bits of data and here we
25:25
finally calculate the temperature
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let's build this and this time I am
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directly running it you can see the
25:43
temperature being displayed on the LCD
25:52
when I hold the sensor there is a rise
25:55
in the temperature
26:05
[Music]
26:16
if you are having issues with the
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temperature values for example if the
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value is 4095
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you can change this delay here don't
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decrease it too much I am reducing it to
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50 microseconds as the time for this
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cycle is 60 microseconds so try to keep
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the delay close to this value
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you can also change this pull-up - no
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Paul this is it guys I hope you
26:56
understood the video you can download
26:59
the code from the link in the
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description keep watching
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[Music]
27:10
[Music]