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STM32 Timers #1 – Generate PWM Output with DMA (Beginner-Friendly HAL + CubeMX Tutorial)
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Jul 11, 2021
Master STM32 PWM generation using CubeMX, HAL, and DMA in this comprehensive tutorial. Learn how to configure timers in STM32CubeMX, set up PWM channels, and leverage DMA for efficient signal output. Perfect for both beginners and embedded developers, this video walks through live examples and register-level explanations to control PWM signals with precision. 🔧 Key topics covered: • Configuring timer parameters in CubeMX • Initializing PWM via STM32 HAL • Using DMA to automate PWM updates • Real-time test signal generation and troubleshooting 📁 Download the code and follow along: https://controllerstech.com/pwm-in-stm32/ 📌 Don’t forget to like, comment, and subscribe for more STM32 tutorials! #STM32 #PWM #CubeMX #EmbeddedSystems #DMA ________________________________________________________________________________________ ******* SUPPORT US BY DONATING****** https://paypal.me/controllertech *******Join the Membership******* https://www.youtube.com/channel/UCkdqtSMnhYuMsJkyHOxiPZQ/join
View Video Transcript
0:00
[Music]
0:09
hello everyone
0:11
welcome to controllers tech this video
0:14
series will be dedicated to the timers
0:16
in stm32
0:18
we will cover all different kind of
0:20
functions that the timers can be used
0:23
for
0:24
starting today we will see how to use
0:26
the pulse width modulation
0:29
this video will cover the pwm output how
0:32
to generate the pwm
0:33
signal how to change the duty cycle or
0:36
frequency
0:37
and how to use dma with pwm
0:41
so let's start by creating the project
0:43
in cube id
0:45
i am using f103c8mcu
0:49
[Music]
0:52
give some name to the project and click
0:56
finish
1:00
first thing we are going to do is set
1:02
the clocks
1:03
this part seems to be confusing for few
1:06
people so pay attention
1:08
i am selecting the hse high speed
1:11
external crystal to provide the clock
1:15
don't randomly use the values i use in
1:17
the videos
1:19
you need to know the crystal frequency
1:21
for your board
1:23
for example you can see in this nucleo
1:26
board
1:26
here is the crystal with eight megahertz
1:29
frequency
1:31
in some nuclear boards this one is not
1:33
present
1:34
but there is another one shared between
1:36
the st link
1:38
and the mcu you can use this one
1:41
also here is another board
1:45
which is comparatively newer and this
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one have the 24 megahertz crystal on
1:50
board
1:51
there is another one right beside it but
1:54
it's 32 kilohertz
1:55
and it's used for the real-time clock
1:57
operations
1:59
so hse in this particular board
2:02
is 24 megahertz
2:04
[Music]
2:06
input the proper crystal value here
2:09
now choose the pll source as hse
2:13
choose the pclk and type in the
2:16
frequency you want
2:19
hit enter and the clocks will be
2:21
configured automatically
2:23
that's it about the clock configuration
2:27
now let's do the rest of the setup
2:30
select the serial wire debug
2:33
i am going to use the timer one for the
2:35
pwm
2:37
there are four channels here and since i
2:40
only need one signal
2:41
i am choosing only channel one you can
2:45
see the pin
2:45
pa8 got selected as the timer one
2:48
channel 1.
2:50
this will be our pin for the pwm output
2:53
signal
2:54
select the clock source as the internal
2:57
clock
2:58
now we need to configure the timer
3:09
here are three formulas that you are
3:11
going to need for the pwm
3:14
first we need to set the proper timer
3:16
clock and that can be done
3:18
with prescaler then the frequency can be
3:21
set using the timer clock
3:23
and the auto reload register the width
3:26
of the signal can be varied using the
3:28
capture compare register
3:30
and the auto reload register
3:33
let's start with the timer clock and the
3:36
prescaler
3:38
first of all we need to know where the
3:40
respective timer is connected to
3:43
this information is provided in the data
3:45
sheet of your mcu
3:48
here is the clock diagram for f103
3:51
and it describes the connection between
3:53
the peripherals and the buses
3:56
here we are looking for the timer 1 and
3:58
you can see that it is connected
4:00
to the ap b2
4:05
now we will check the clock setup we did
4:08
and here you can see the ap b2 timer
4:10
clock is running at 72 megahertz
4:13
remember one thing
4:15
since we are using timer we are
4:17
concerned about the timer clock
4:19
not the peripheral clock since the timer
4:22
1 is connected to apb2
4:24
the timer 1 clock is also 72 megahertz
4:27
right now
4:29
so we need to bring this clock down to
4:31
our workable range
4:33
and that's where the prescaler comes in
4:36
timer clock is equal to abp timer clock
4:40
divided by the prescaler
4:42
apd timer clock is at 72 megahertz
4:46
so if we use the prescaler of 72 the
4:49
timer clock would come down to 1
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megahertz
4:52
the prescaler value must be 1 less than
4:55
the actual
4:56
value this is explained in the prescaler
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register
5:00
as you can see this one here gets added
5:03
with the value we input
5:05
so make sure the value should be 1 less
5:07
than the desired value
5:09
so if you keep the prescaler 0 it would
5:12
mean the actual prescaler is 1.
5:15
now our timer clock is at 1 megahertz
5:19
remember that frequency is equal to
5:21
timer clock divided by auto reload value
5:24
so if i choose the auto reload value of
5:27
100
5:28
the frequency will be 10 000 hertz
5:31
the value for the arr should also be one
5:34
less than the actual value
5:36
these registers are set up in this way
5:39
and that's how we should use them
5:41
so our timer clock is running at 1
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megahertz and using the auto reload of
5:46
100 will bring the frequency to 10
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kilohertz
5:55
that's all we need to set up here and
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the rest we will take
5:58
care in the code let's enable the dma
6:02
also
6:02
[Music]
6:04
here we are going to send the data to
6:06
the pwm
6:08
so the direction will be memory to
6:10
peripheral
6:11
keep the dma mode normal so that we can
6:14
control when to send the data
6:16
and the data width must be half word as
6:19
we will be sending 16 bit values
6:22
that's all the setup we need let's click
6:25
save to generate the project
6:28
we will start with the simple pwm signal
6:32
load the value in capture compare
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register
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i am using ccr1 because i have selected
6:39
channel 1.
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if you are using any other channel use
6:43
the respective ccr register
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i will explain this 50 in a while
6:49
and start the timer in pwm mode
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let's build and run this for now
6:59
all right let's see the output
7:08
you can see the frequency is 10
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kilohertz and the duty is 50 percent
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let's see some calculations
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the frequency is equal to 10 kilohertz
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and we know that the duty is equal to
7:24
ccr divided by the auto reload value
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i have used the ccr of 50 and the auto
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reload is 100
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so the duty percentage is 50
7:36
let me explain you how this works the
7:39
timer clock is set at 1 megahertz
7:42
so each count in the counter will take 1
7:45
microsecond
7:46
the auto reload is set at 100 so the
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total counts the counter can count are
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100
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after 100 the counter will overflow and
7:58
start from zero again
8:00
also remember that we have set the
8:02
capture compare value to 50.
8:05
so the pulse will remain high until the
8:08
counter reach this value
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50. once the counter hit this value
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the pulse will go low for rest of the
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counts
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so this make the pulse high for 50
8:18
microseconds
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and low for 50 microseconds
8:21
[Music]
8:24
now let's change the ccr to 30.
8:42
the duty cycle is 30 percent now
8:46
also note that the pulse is high for 30
8:48
microseconds
8:49
and the low for 70. this is because the
8:52
capture compare value
8:54
is set to 30. let's change the auto
8:57
reload period to 10.
9:05
also change the ccr to 4.
9:12
now our frequency is 1 megahertz by 10
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that is 100 kilohertz and
9:19
duty cycle will be 40 percent
9:23
let's test it
9:24
[Music]
9:30
you see the frequency is around 100
9:33
kilohertz
9:34
and the duty is 40
9:39
so this is how we send the pwm signal
9:43
now we will use the dma with the pwm
9:47
let's define an array to hold 10 values
9:50
that we are going to send to pwm
9:53
[Music]
9:54
now we will set the values the values we
9:57
are going to send
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are for the ccr register
10:07
these values are the duty cycles and
10:09
they will change with every pulse
10:12
start the timer in the pwm and dma
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the data is the pwm data and the length
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is 10.
10:39
also i am changing this back to 100 as i
10:43
have used the ccr of 10 to 100
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let's run this
11:04
here we have the pulse with different
11:06
widths
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it starts with 10 percent duty and goes
11:10
all the way to 100
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duty cycle since we have used the normal
11:15
mode
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the dma will only run once and after the
11:18
transfer is complete
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it will stop the dma can be used in the
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situation
11:24
where the pulse needs to be changed very
11:26
frequently
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one of such examples are while using the
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addressable rgb
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leds there is already a tutorial on it
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you can find the link in the description
11:39
if you don't want to keep the pulse high
11:41
in the end you can send a zero in the
11:43
end
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to indicate the end of transfer or
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something like that
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so we saw how to use pwm output how to
11:51
change the duty cycle and frequency
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and how to use the dma with pwm
11:57
this is it for this video the next video
12:00
will cover the pwm
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input where we can measure pretty high
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frequencies
12:06
later i will cover other functions of
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the timers
12:09
that's it for today you can download the
12:12
code form the link in the description
12:16
keep watching be safe and have a nice
12:18
day ahead
12:25
[Music]
12:35
you
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