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hello everyone welcome to controllers
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tech today in this video I will show you
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guys some basic DAC working first I will
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show what digital to analog converters
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are used for and then we will create a
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sine wave using DAC in stm32 digital to
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analog converters are basically opposite
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to ADC they convert the digital signal
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to the analog signal and as the sine
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wave is the best representation of an
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analog signal that's what we will create
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today let's start with the cube ID first
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I am using stm32f4 for six ref1 zero 3 c
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8 don't of DAC so I have to use this one
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let's set up the cube mix first things
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first I am using the external crystal
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for the clock next select the DAC
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configuration as you can see here the
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pin pa4 is selected as DAC out pin by
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default output buffer is enabled and
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there is no trigger we will keep it like
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this for the first part of this video
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next setup the clock and once done click
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Save to generate the code
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here is the generated main.c file before
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starting let's see the document provided
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by st on DAC as you can see the formula
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here to calculate the DAC output the ref
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is 3.3 volts DOR is the value that we
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don't know max digital values are given
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depends on what resolution you use let's
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start programming now
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first of all I am creating a variable
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0.2 is going to be the output voltage
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that is DAC output value we need to
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create another variable to store the
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respective digital value inside the main
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function first start the DAC in this
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while loop I am going to do the
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conversion from voltage to the digital
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value to do so we need to make do R as
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the subject of this formula
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once done we need to set this value to
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and then increment the value this
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process will continue with some delay
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remember that the value can't be more
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than reference voltage and that is 3.3
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looks like we got some errors
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let's compile it again
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so the code compiled successfully time
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to flash it to the board just create a
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observe the reading on the voltmeter and
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on the oscilloscope the voltage output
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from the pin is changing every 750
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milliseconds and it doesn't go higher
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let's increase the time delay so that
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you can observe the change properly
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here we go the voltage is increasing
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every two seconds now so this was the
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basic idea about how to use the DAC in
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stm32 now we will create a sine wave
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using the same this process is mentioned
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in the same note but before this we need
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to make some changes to our setup
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first we need to select a trigger timer
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I am using timer 2 also we will use DMA
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for this entire process this will keep
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next go to the timer setting that you
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chose this setup will decide the
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frequency of the wave and therefore is
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critical I am using timer 2 which is
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connected to the a PB 1 o'clock and this
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is running at 90 megahertz I am
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selecting the prescaler as 90 this will
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reduce the timer clock to 1 megahertz
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using a RR as 100 will further divide
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the clock to 10 kilo Hertz I will
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explain this particular setup in a while
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select update events here this is it for
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the setup let's generate the code now
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include math.h so that we can use the
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I am creating an array to store the
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digital values of 100 samples of sine
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function we need pi value this function
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here will do the conversion let's take a
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look at the PDF again this is the
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formula that we are going to use number
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of samples is going to be 100 in our
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case f FF is for the 12 bit resolution
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now in the main function we first need
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to start the timer and then start the
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now let's talk about the frequency of
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as I mentioned the APB clock is at 90
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megahertz and using a pre scalar of 90
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will divide that clock by 90 making it
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one megahertz using the AR AR value 100
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will further divide the clock by 100
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making it 10,000 Hertz according to this
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application note the frequency of the
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sine wave is equal to time of frequency
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divided by number of samples in our case
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we have to further divide this value by
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100 because we are doing 100 samples
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which gives us a frequency of 100 Hertz
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this is the frequency that I am
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expecting for the sine wave to have
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oh sorry I forgot to include the
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function to convert the values to
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let's build and run the code
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you can see the sine-wave being produced
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with the frequency of 100 Hertz
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let's increase the frequency now
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I am dividing it by ten that will
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increase the frequency by multiple of
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ten now the frequency should be 1,000
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you can see the frequency is 1 kilo
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Hertz this is it guys I hope you
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understood the video I will do more
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tutorials on DAC in future we will
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generate the triangular waves and noise
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waves too you can download the code from
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the link in the description keep
