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STM32 TIMERS #9. One Pulse Mode
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Mar 4, 2023
Purchase the Products shown in this video from :: https://controllerstech.store ________________________________________________________________________________________ STM32 Timers PART8 :::: https://youtu.be/gfSWsqHdyQA STM32 Timers PART10 :::: https://youtu.be/0RsL_F3Nxn0 STM32 TIMERS Playlist:::: https://www.youtube.com/playlist?list=PLfIJKC1ud8gjLZBzjE3kKBMDEH_lUc428 PDF shown in the video :::: https://www.st.com/resource/en/product_training/STM32L4_WDG_TIMERS_GPTIM.pdf STM32 Playlist :::: https://www.youtube.com/playlist?list=PLfIJKC1ud8gga7xeUUJ-bRUbeChfTOOBd DOWNLOAD THIS PROJECT FROM :::: https://controllerstech.com/stm32-timers-9-one-pulse-mode/ ________________________________________________________________________________________ ******* SUPPORT US BY DONATING****** https://paypal.me/controllertech *******Join the Membership*******
View Video Transcript
0:00
foreign
0:01
[Music]
0:04
Tech
0:06
[Music]
0:12
this is the ninth video in the SDM 32
0:15
timer series and today we will cover the
0:18
one pulse mode
0:20
one pulse mode is used to generate a
0:22
pulse of a programmable length in
0:24
response to an external event
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the pulse can start as soon as the input
0:29
trigger arrives or after a programmable
0:32
delay
0:33
I have here a PDF explaining the
0:35
different modes of stm32 timers and here
0:39
is the one pulse mode
0:41
I will leave the link to the PDF in the
0:43
description of the video
0:45
as mentioned here the capture compare
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registers value defines the pulse start
0:50
time and the auto reload value defines
0:53
the end of the pulse
0:55
so basically the effective pulse width
0:58
is the difference between the auto
1:00
reload and the CCR values
1:03
we can also program the output to be a
1:06
single pulse or a continuous pulse train
1:09
started by a single trigger
1:11
there is also a retricorable option
1:14
where the pulse width will simply extend
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if a new trigger arrives before the
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output pulse goes low
1:20
we will cover everything shown here in
1:22
this video
1:24
let's see this in working and we will
1:26
start by creating a new project in the
1:29
cube IDE
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I am using stm32f446re
1:36
give some name to the project and click
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finish
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first of all I am selecting the external
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Crystal for the clock
1:45
the board has 8 megahertz Crystal on it
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and let's run the system at 90 megahertz
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clock
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this will keep both the APB clocks at
1:54
the same 90 megahertz frequency and we
1:57
don't have to worry about which timer is
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connected to which APB bus
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let's configure the timer now
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I am using timer 1 for this application
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select the slave mode as the trigger
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mode
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in trigger mode the counter starts at a
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rising edge of the trigger but it does
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not reset
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the trigger source is set to
2:20
ti2fp2 that is the channel 2 of the
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timer
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I am selecting Channel 2 for the trigger
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because I am going to use Channel 1 for
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the output
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you can see the pin pa9 has been
2:32
selected as the channel 2 pin and this
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pin will be used as the input signal
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set Channel 1 in the output compare mode
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the pin pa8 will be used as the output
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pin for the timer and here we will
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measure the one pulse generated by the
2:50
timer
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make sure to enable the one pulse mode
2:55
now we will configure the timer's
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parameters
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since the APB timer clock is at 90
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megahertz a prescaler of 90 will bring
3:04
the clock down to 1 megahertz
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now the counter is counting at 1
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megahertz so each count will take one
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microsecond
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I am setting the auto reload to 50 000
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so the counter period will be 50
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milliseconds
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this is also going to be the maximum
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pulse width if we keep the capture
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compare register at minimum
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the trigger polarity for the input
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signal is set to a rising Edge
3:32
we will change the mode of the output
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compare later in the code the pulse is
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basically the start time for the
3:39
generated pulse and I am keeping it at
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10 000 that means 10 milliseconds
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I have set the auto reload value to 50
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000 which represents 50 milliseconds
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this makes the effective pulse width of
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40 milliseconds for the output signal
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that's all we need to set up in the cube
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MX click save to generate the project
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let's see the connection first
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here the black wire is connected to the
4:09
pin pa9 which is the input pin and is
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connected to the button
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the other end of the button is connected
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to the 3.3 volt pin on the board
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so if I press the button the pin pa9
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will be pulled High to 3.3 volt and the
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timer will recognize this as the trigger
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signal the blue wire is connected to the
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pin pa8 which is the output pin on
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Channel 1 and is connected to the logic
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analyzer where we will monitor the
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output signal
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go to the timer initialization function
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here in the output compare mode open the
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Declaration of the predefined mode
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out of the listed modes choose the pwm2
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mode
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this configuration is not available in
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Cube MX so we need to manually do it
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here
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now in the main function start the timer
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in the one pulse mode
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I am using timer 1 channel 1.
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let's build and run the code now
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we will see the result in the logic
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analyzer
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you can see whenever I am pressing the
5:40
button there is a pulse being generated
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in the output
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if you see the pulse width it is
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approximately 40 milliseconds
5:50
this is as per the setup we did for the
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timer
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we set the pulse start to 10
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milliseconds and auto reload to 50
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milliseconds and the width is the
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difference between them that is 40
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milliseconds
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now let's see how to generate multiple
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pulses with a single trigger
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here in the timer configuration the
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repetition counter was zero and this
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would generate only one pulse
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now let's assume that I want to generate
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eight pulses
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to do that I need to update the value 7
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here
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let's see how this is working
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you can see when I am pressing the
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button multiple pulses are being
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generated
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there are a total of eight pulses each
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having the width of 40 milliseconds
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let's say if we want to generate the
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pulse with a software trigger instead of
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an external signal
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for this purpose we will use the
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internal trigger mechanism between the
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timers in stm32
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open the reference Manual of your
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controller and search for the internal
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trigger connection
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here you can see the timer 1 can be the
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slave to all these timers
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and if I want to use the timer 2 as the
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master I have to use the itr1 signal to
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trigger the timer 1.
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let's configure the timer too now
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here I am selecting the clock source as
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the internal clock
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the timer 2 is also running at 90
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megahertz and using the prescaler of 90
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will bring down its clock to 1 megahertz
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since the pulse width is set to 40
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milliseconds in timer 1 I am going to
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choose the trigger period higher than
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that
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the auto reload value of 60 000 will
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generate the trigger every 60
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milliseconds
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set the trigger event selection to
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update event
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now in the timer 1 we will set the
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trigger source to itr1
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you can see the channel 2 pin pa9 has
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been disabled since the trigger has been
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changed to internal now
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the rest of the configuration is
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unchanged
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let's generate the project now
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here the repetition counter has been
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changed back to zero
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and let's change this to the pwm2 mode
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we also need to start the timer too so
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that it can generate the trigger
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let's build and run the project now
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here you can see the pulse is high for
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40 milliseconds and then low for 20
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milliseconds
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the timer 2 is generating the trigger
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every 60 milliseconds and therefore we
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see the pulse being low for 20
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milliseconds
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so we saw how to use the one pulse mode
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with single and multiple pulses and also
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how to use the software trigger to
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generate the pulse now we will see the
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retriguable one pulse mode
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in order to use the retreigurable mode
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the timer must be set in the reset and
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Trigger mode combined
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but this option is not available in the
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f446re
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actually the retriggerable mode is not
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available in many controllers and
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therefore I am going to use the F750
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Discovery board for this purpose
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I am going to use the same clock here so
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that the configuration would remain the
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same
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I am using timer 3.
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here you see the combined reset trigger
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mode it is available
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the trigger source is selected as
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Channel 2.
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the channel 1 is being used as the
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output compare mode
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enable the one pulse mode
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here you can see the two pins for timer
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3.
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I am going to use another pin for
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channel 2 that is the PIN pc7
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this is because I have this pin
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available for connection
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here pc7 is going to be the input pin
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for channel 2 and pb4 is going to be the
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output pin
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since the clock is the same I am keeping
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the same configuration
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make sure to keep the pulse 0 for a
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triggerable mode to work
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for the output compare select the mode
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as retriguable one pulse mode 2.
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that's it for the configuration click
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save to generate the project
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I forgot to select an output pin so
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let's select the pin PA 0.
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the trigger signal will be provided by
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this pin pa0
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let's see the connection I made for this
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board
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the black wire is connected between the
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pin PA 0 and the timer input pin pc7
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the blue wire is connected to the timer
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output pin pb4 and to the logic analyzer
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in the main function start the timer in
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one pulse mode
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now in the while loop we will toggle the
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PIN pa0
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the total time before the pin goes high
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again is 40 milliseconds also keep in
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mind that the pulse width is set to 50
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milliseconds so the trigger will happen
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before the pulse goes low
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and if the retriggerable mode works the
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pulse width will be extended
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let's build and run this
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here you can see the pulse remain high
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and never goes back to low
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this means the retreigurable mode is
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indeed working
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let's change this delay so that the
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trigger will take place every 60
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milliseconds
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our pulse width is 50 milliseconds so
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now we should see the pulse going low
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here you can see the pulse is high for
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50 milliseconds and low for 12
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milliseconds
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the extra two milliseconds could be due
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to whole processing time
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let's change this to a total of 45
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milliseconds delay
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now the pulse is again being extended
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because the trigger is happening before
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the pulse goes low
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if we try something similar without the
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retriguable option being selected this
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won't work
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the pulse extends only when the
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retriguable option is enabled
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this is it for the video
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I hope you understood the different
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configuration is the one pulse mode
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I will continue the timer series with
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other modes in the upcoming videos
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you can download the code from the link
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in the description
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leave comments in case of any doubt
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keep watching and have a nice day ahead