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STM32 Dual Core #4. Inter core comm || FreeRTOS || OpenAMP || IPC || Shared Memory
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May 27, 2023
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View Video Transcript
0:00
foreign
0:01
[Music]
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Tech
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this is yet another video covering the
0:15
inter-core communication between the
0:17
stm32 CPUs and today we will see how to
0:20
use the free rtos with the open amp
0:24
this is the continuation from the
0:26
previous video so if you haven't watched
0:28
it please watch the previous video first
0:32
I will continue from where I left off in
0:34
that video
0:36
we will basically do the same where the
0:39
M7 core which is the master will send
0:42
the data to the M4 core the slave
0:45
the data will be then sent to the UF by
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the M4 core
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the explanation has been covered in the
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previous video so I will just focus on
0:54
the rtos part
0:57
this is the previous project we covered
1:00
we need to enable the rtos so let's go
1:04
to the cube MX
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enable the free rtos for cortex M4
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go to the tasks and cues tab
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here the default task is already created
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so we will just change its name to the
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RX task
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the RX task will be used to receive the
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data from the master
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note that its priority is set to normal
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let's create one more task the TX task
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it will be used to send the data to the
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uart
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we will keep its priority lower than the
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RX task so I am setting it to below
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normal
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now add one binary semaphore so that we
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can restrict TX task from sending data
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continuously
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that's it for the cortex M4 enable the
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rtos for the cortex M7
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we will again create two tasks here one
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for sending the data to the slave and
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another one for receiving the data from
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the slave
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though we are not going to receive any
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data from the slave we still need to
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check for the message to know if the
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service has been destroyed by the slave
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we don't need any semaphore here as we
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will send the data periodically
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since we are using our TOS we need to
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use a Time base other than the systick
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so I am enabling the timer 6 for the
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cortex M7 and timer 7 for the cortex M4
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now select the appropriate time base
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source
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that's it for the configuration click
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save to generate the project
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there is a warning about the new library
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re-entrant but that's all right go ahead
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and generate the code
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let's build both the files once
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I will start with the cortex M4 first
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this part is used to initialize the open
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amp and create the endpoint
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we will put it inside the RX task and it
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will only run once in the beginning
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since the RX task has higher priority it
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will run first and initialize the open
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amp
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after the initialization is over it will
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acquire the semaphore so the TX task
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does not run
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the TX task is responsible for sending
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the data to the uart so this part goes
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there
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we will shield this with the semaphore
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so to send the data first it has to
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acquire the semaphore
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since we are using rtos we will use the
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Malik and free functions to create an
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array of characters
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so the TX task needs to acquire the
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semaphore before sending the data but
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the semaphore is already acquired by the
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RX task
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therefore once the message is received
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we will free the semaphore so that the
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TX task can acquire it and send the data
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now inside the RX task we will
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continuously check for the data sent by
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the master
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finally the RX task is as follows
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once the control enters it the open amp
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will be initialized
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then the end point is created and it
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will acquire the semaphore
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then it will continuously check for the
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data sent by the master every 10
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milliseconds
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once the data is received the data will
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save in the variable and the semaphore
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will be released
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after that the TX task will send the
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data to the uart and again try to
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acquire the semaphore
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let's delete this
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also the data is defined in the TX task
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itself
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that's all for the slave now we will
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write the code for the master
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here I am leaving the message as one
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we will again copy the initialization
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inside the RX task
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after the initialization is over the RX
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task will check for the message from the
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slave
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and now the transmission of data will
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take place in the TX task
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it will run every second
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as I mentioned the slave is not sending
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any data so the check for message is
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only used to check if the service is
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destroyed by the slave
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the master should only check for message
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if the service is created and if it is
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destroyed the open amp will
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de-initialize
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all right let's build and Flash the code
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I am using the same debug configuration
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from the previous project
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let's reset the board
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here you can see the message is being
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printed on the console every one second
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so our project is working fine so far
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now let's say I want to de-initialize
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the open amp after some time
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If the message value is equal to 15 the
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slave will de-initialize the open amp
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and also terminate the TX and RX tasks
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this will destroy the service and the
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master should also do the same
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when the tasks are terminated an ideal
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task should run in both the cores and we
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will see this while debugging the
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project
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terminating tasks is not the ideal
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solution
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rather you can just suspend them and
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write a separate task for initializing
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the open amp again and then resume the
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tasks to do their job
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I am just terminating them so that the
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TX task does not try to send data while
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the open amp is de-initialized
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for debugging we use the same
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configuration for M7 core but make sure
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the M4 file here is on the top
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then go to the cortexm4 main file and
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create a new debug configuration
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select none under the reset Behavior
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make sure the port number is at least 4
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higher than the M7
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go to the startup tab double-click on
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the configuration and uncheck the
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download option
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now debug using the M7 configuration
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when fully loaded again load the M4
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configuration
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all right now select both the main files
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using the control button and click run
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the message is being printed
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and it stopped at 14 because as soon as
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it reached 15 the open amp was
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de-initialized and the tasks were
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terminated
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hence the TX task could not send the
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message to the console
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if you pause the debugger now you can
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see the ideal tasks are running in both
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the cores
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so we saw how to de-initialize the open
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amp after a certain condition was met
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now let's quickly see how to transfer a
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string or some character data
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here I am creating another variable in
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the M4 core
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this is a character pointer
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inside the receive callback function we
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will simply type cast the data into the
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character pointer
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since we are receiving the data in the
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character form we will use the S format
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rather than U
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the rest of the code remains unchanged
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for the master I am first defining the
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string I am going to send
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and while sending the data I am using
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the string length function to calculate
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the length here
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make sure to add a 1 to the length
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it should be an array
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all right let's run the code again
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you can see the string is being
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displayed on the console
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so I hope you understood how to use the
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open amp with free rtos and how to send
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the string or characters between the
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cores
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I will make more videos covering more
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methods to do the same
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I will also make a video covering a
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practical application of inter-core
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communication
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that's it for this video
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the link to download the code is in the
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description below
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leave comments in case of any doubt
12:08
keep watching and have a nice day ahead
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