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hello everyone welcome to controllers
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tech today in this tutorial we are going
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to see how to manage multiple you arts
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using head and tail method both the you
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arts would be able to receive and
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transmit data of unknown length and
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after this video you will be able to use
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all those sensors that require serial
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transmission to work the serial
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communication based sensors for example
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esp8266 GPS GSM etc need to have one
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dedicated you are --court to communicate
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with the center and another uart port
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should be connected to the computer
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that's why I am using to you arts in
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this video let's start the cube ID and
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create the stm32 project I am using f4
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give some name to this project and click
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Here I am enabling the external crystal
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next I am selecting usart one you can
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see the baud rate by default is 11 5 200
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I am going to keep all settings as it is
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and enable the interrupt for you Sark 1
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along with that I am using usart 2 with
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let's first take a look at the
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you can see how the devices are
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connected so the u r2 is connected to
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the computer and UART one is connected
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to the serial device I am using esp8266
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for this purpose in both the connections
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the TX pin of the controller must be
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connected to the Rx of the device and rx
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to TX of device let's go to the clock
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HSE means I want to take clock from
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external crystal which is of 8 megahertz
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check the PLL clock and I am typing in
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the maximum frequency possible and hit
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enter now the setup is done so just
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click Save and the project will be
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this is our main dot C file now first of
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all include the libraries for the UART
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ring buffer multi you will get these
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files in the source and the include
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folders after you download the code
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exactly where I am placing them let's
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open the header file first here I have
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written the description for all the
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functions available here you can change
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the default size of the buffer then we
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have UART read UART write send string
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functions same as the previous ring
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buffer tutorial I did note that all
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these functions now take UART as a
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parameter this is to make sure that we
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send the data to the respective UART
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so we have all the previous functions
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except this one get after this one here
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saves the entered number of characters
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into the provided buffer after some
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particular string is matched I will show
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you how to use it in a while let's see
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what changes have I made in the UART
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ring buffer dot C file
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here you can define the names for the to
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before proceeding any further let's copy
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this in the interrupt file
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so basically we are redirecting the
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interrupt to use the code written by us
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and not the default one let's go back to
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the ring buffer dot C file
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notice here that I have defined
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everything twice for the two you arts I
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let's see the UART read function the
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parameter is the UART type if the UART
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is the UART one which we have defined up
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here in the beginning every operation
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will be corresponding to the rx buffer
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and in case the UART is UART to the
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operations will be corresponding to the
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rx buffer - same things for the UART
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get position function gives the position
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of the string and the incoming data and
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the given UART I will show you how to
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and we have all these regular functions
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available let's go to the main dot C
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file and start programming this
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first of all include the header file for
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the UART ring buffer I am defining some
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new names to the you arts so it would be
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easier to remember them as I mentioned
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UART 2 is connected to the computer and
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UART 1 is connected to the Wi-Fi that's
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why I am naming them PC you are and
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Wi-Fi UART inside the main function
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first of all we need to initialize the
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ring buffer and then in the wild loop I
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am writing the condition that if the
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data is sent from computer receive it
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and then write to the Wi-Fi
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and if it is sent from the Wi-Fi then
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write it to the computer
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this is pretty much for now let's build
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this there are no errors in this let me
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connect my controller before debugging
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ok it's connected let's debug the code
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select the stm32 application here
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so the debugger is connected you can add
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these buffers to the live expression I
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will use real term for the serial
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the controller is connected to the port
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5 let's start the session I am sending
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the 80 command and the response is as
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expected you can check all these buffers
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to verify data so basically the computer
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sends the data which is received by
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microcontroller which send it to the
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Wi-Fi then Wi-Fi sends the response back
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which is received by controller and then
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sent to the computer again that is the
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response that you see on the terminal I
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am typing another command and you can
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see the data sent by the Wi-Fi is being
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displayed on the terminal
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this is the reset command and that's the
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response from the Wi-Fi I am NOT going
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to show you how to interface the esp8266
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in this video this is just to test if
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the multiple you arts are working
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alright or not so everything seems to be
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working good till now now the important
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part in all these situations either you
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use the Wi-Fi GPS or GSM devices we need
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some particular data from the incoming
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stream and we don't know when that data
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is going to show up for example suppose
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I want to know the SDK version as shown
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on the terminal here all I need to know
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is that it is going to be after SDK
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version and it's five characters in
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length to get those values I am going to
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use the get after function
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first I am defining a buffer which can
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hold those five characters as this data
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is sent from the Wi-Fi I am writing this
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inside the Wi-Fi part string is that
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string that you want to wait up to there
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are five characters I want to store them
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in the buffer and they are being
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received from the Wi-Fi you are this
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must be put in the if loop once the
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characters are received the function
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will return one and we can proceed with
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our code here I am writing the program
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to send the string to the computer and
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after that it will send the characters
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that are stored in the buffer
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let's build this and run
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I am sending the reset command first and
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as you can see nothing is being
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displayed on the terminal this is
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because the get after function is
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working in the blocking mode and it is
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waiting for the characters
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I will try sending a T command and
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nothing again although we don't see
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anything printed here but the data is
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still being saved in the rx buffer you
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can see the response from the Wi-Fi for
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the a T command now once I send the GMR
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command you can see some data printed on
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the terminal this is same what we would
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expect the string in the stored
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characters this number printed here is
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the position of the string in the rx
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buffer I was doing some debugging so I
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guess I forgot to remove the function
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let's test the function now
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it's working good now I will try to look
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for another string now
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this time I will print the 80 version
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the version number is of 8 characters so
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I am changing number of characters to 8
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also I am looking for a TV on in the
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data and edit buffer so it can store at
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least 8 characters as you can see it is
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displaying the version number as we were
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expecting it to display this is it for
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I hope you understood it and you will
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apply this in your projects I will just
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add an example here so that you guys
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remember about the usage this function
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is very important in terms of using any
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serial based sensor as the data length
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is unknown and what we want can come at
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you can get the header file in the C
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file inside the source and include
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folders after you download the code
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leave any comments in case you have
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doubts keep watching
