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this is the 10th video in the SDM 32
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timer series and today we will see
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another application of the timer in
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we will see how to use the timer in the
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you can use this application note
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an4013 to see the timer applications
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we have already covered other slave
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modes which includes reset mode trigger
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mode and combined reset and Trigger mode
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so today we will finally see the Gated
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as mentioned here in gated mode the
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counter clock can be controlled by the
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also both the start and stop of the
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counter can be controlled
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basically I am going to use a button to
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control the trigger signal and the timer
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will output a pwm wave
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when the button is pressed the trigger
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will go low this should enable the
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counter and the timer will output a pwm
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when the button is released the trigger
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goes High the counter clock will be
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disabled and so does the pwm output of
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I will also cover how to automate this
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process where a fixed pwm signal will be
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generated at a fixed rate
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we will see the connection diagram in a
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while let's start the cube IDE and
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stm32f446re nucleo board
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give some name to the project and click
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we will start with the clock first
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I am selecting the external Crystal to
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provide the clock for the controller
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the board has 8 megahertz Crystal and I
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want to run the system at maximum 180
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now let's configure the timer 1 in the
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select the Gated mode under the slave
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since I want to use the button for the
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trigger the trigger source is set to ti1
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this will enable Channel 1 for the
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trigger and here you can see the pin p8
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has been enabled where we will connect
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I am setting the trigger polarity to the
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now let's configure Channel 2 for the
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timer 1 is connected to apb2 bus which
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is running at 180 megahertz right now
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using a prescaler of 180 will bring down
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the clock to 1 megahertz
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the counter value of 1000 will further
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reduce the clock to 1 kilohertz and this
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will be the output frequency of the pwm
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I am using the pwm mode 2 and I am
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setting the pulse at 500 which is 50 of
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the auto reload value therefore the pwm
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duty cycle will be 50 percent
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if you don't understand the pwm
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configuration watch the pwm video in the
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so this is it click save to generate the
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let City Connection now
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I have connected the button between the
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ground pin and the pa8
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the pin pa9 is connected to the logic
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analyzer where we will see the pwm
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let's write the code now
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in the main function we will simply
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start the timer in the pwm mode
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I am using timer 1 and channel 2.
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let's build and run the code now
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we will see the output in the logic
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I have connected the output of the
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button to channel 1 and the pwm output
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here you can see whenever the button is
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pressed the output on Channel 1 goes low
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and along with it we see the wave being
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generated on Channel 2.
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the pwm signal continues as long as the
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button is pressed and when it is
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released the signal also stops
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if you zoom in here you can see the pwm
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signal has a frequency of one kilohertz
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and the duty cycle is 50 percent
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this is as per the setup we did for the
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so this is working well with the pwm
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signal being controlled by the button
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now let's say we want to automate this
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process where we want to generate the
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pwm signal of the same one kilohertz
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frequency at some fixed rate
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before we use another timer for this
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let's see the MCU reference manual
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here if you look for the internal
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trigger connection you will find a table
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I have already explained this in the
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previous time of videos
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here you can see that the timer 1 is a
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slave to the timer 2 and it can be
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controlled via the signal itr1
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so we will change the trigger Source
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the channel 1 pin has been disabled
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since we are using the internal trigger
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we will use the timer 2 to generate the
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trigger signal at some fixed rate
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here we will generate the pwm signal
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this is because the output will be used
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for the trigger signal
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timer 2 is connected to the apb1 bus
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which is running at 90 megahertz right
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using the prescaler of 90 will bring
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down the clock to 1 megahertz
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the auto reload value of 100 000 will
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further reduce the clock to 10 Hertz
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this is the rate at which the pwm will
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the trigger event is set to Output
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compare of Channel 1.
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I am using the pulse value of 50 000
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which is half the auto reload value and
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this will make the duty cycle 50 percent
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this will keep the trigger signal high
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and low for an equal amount of time
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this is it for the setup let's generate
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here in the main function we will start
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the timer in pwm mode
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we are using channel one of the timer 2.
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let's build and Flash the code to the
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here you can see the pwm being generated
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the time difference between two signals
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is 100 milliseconds which corresponds to
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the pwm signal is still one kilohertz
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that we set in the timer 1. so we
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finally have a pwm signal of one
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kilohertz being generated at a rate of
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this is it for the video
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I hope you understood how to use the
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Gated mode in the timer
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you can download the code from the link
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leave comments in case of any doubt
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keep watching and have a nice day ahead
