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welcome to controllers tech few months
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ago I did a video on how to create delay
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in microseconds using DWT although it
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worked perfectly there were some
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microcontrollers which does not support
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DWT especially the f0 series and the F 3
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series microcontrollers so today in this
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video I will show you how to generate
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delay in microseconds and nanoseconds
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across all the stm32 controllers and to
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do so I am going to use the timers let's
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start with the cube MX first I am using
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okay now the clock is set to the maximum
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note that the APB to clock is at 180
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megahertz and the APB 1 clock is at 90
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megahertz now let's take a look at the
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timers in the datasheet note that time
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of 1 is connected to the APB - so I am
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going to use that for the delay because
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in order to create delay in nanoseconds
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I need at least hundred megahertz clock
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frequency for the timer set the timer at
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now like I said I need hundred megahertz
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for the delay in nanoseconds and it will
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give me a delay of 10 nanoseconds
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unfortunately I cannot go lower than
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so the prescaler value is going to be
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zero because we cannot divide the APB
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clock any further I am writing one one
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minus one just to indicate that whatever
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value is input here the microcontroller
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is going to add one to it so our actual
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value is 1 and we are subtracting one
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for the microcontroller to add it later
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the auto reload register for timer 1 is
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16-bit so I will input the maximum value
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here and that is 0 cross F F F F which
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turns out to be 65,536 in decimals also
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I am setting pin p1 as output so that we
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can measure the frequency in an
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let's write the code now okay
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first of all I will create a function
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for the delay whose parameter is going
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to be the delay we want remember that if
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you input value one here that's going to
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be a ten nanoseconds delay because our
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clock is at 100 megahertz inside this
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function we will set the counter to zero
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and then let the counter increment until
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it reaches the input value that we have
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provided each count takes ten
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nanoseconds in this case once it does
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the control will come out from the loop
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also remember that we cannot use the
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delay higher than 65,536
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because that's the limit for our counter
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as it is only 16 bits if you want higher
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values you have to use a 32 bit timer
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but in my case the maximum clock to the
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32 bit timers is 90 megahertz so I
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inside the main function let's toggle
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the pin after some delay
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so if the delay is one that's going to
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be ten nanoseconds now 100 nanoseconds
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1000 900 second 10 microseconds 100
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microseconds I am using this higher
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delay because I don't have means to
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measure the high frequencies so this
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hundred microseconds is going to give me
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a frequency of 10 kilohertz which I can
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measure but as the pin will toggle after
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every 100 microseconds the oscilloscope
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is going to read it as 5 kilohertz
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because this one reads the frequency off
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pin toggling make sure you initialize
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the timer in its normal mode let's build
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this code and test it if you want one
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nanoseconds delay your controller
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frequency should be at least 1 gigahertz
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similarly if you want the delay in
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microseconds all you have to do is use
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the pre scalar to divide the main time a
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clock to get a 1 megahertz frequency so
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the pre scalar value in that case would
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as you can see here the frequency is 5
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that means the nanosecond delay is
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let me reduce the delay a little so that
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we can increase the frequency now I am
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using 50 microseconds delay technically
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this should give me the frequency of 20
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kilohertz but like I said the
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oscilloscope is going to read the
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frequency of pin toggling it is going to
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read it as 10 kilohertz
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as you can see it's reading 10 kilohertz
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I hope you understood this guy's this
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should work across all stm32 devices if
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you choose the timer's properly by
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taking a look at the datasheet this is
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keep watching have a nice day
