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welcome to controllers tech today in
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we will see how can we send and receive
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data from the computer
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without using uart i will use the usb to
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i have already made a video on it but
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that video only covers the sending part
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and this video will cover both the
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sending and the receiving parts
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let's start by creating the project in
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first i am using stm32f103c8 controller
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give some name to the project and click
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here is our cube mx i am selecting the
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external crystal for the clock first
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select serial wire here now
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in the usb select the device
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in the usb device settings select the
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class as communication device class
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leave everything to default here i will
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change this name to see if it shows up
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that's all here now go to clock setup
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i will set the clock manually i have
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eight megahertz crystal
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and i want the system to run at maximum
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note here that usb clock is
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automatically set to 48 megahertz
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that's all for the setup click save to
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the functions used to send or receive
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data can be found in usbd
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but if you look into the header file
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there is only a function available
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and that is to transmit data we will
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modify the receive function in a while
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here is the limit for the send and
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receive buffer you can change them
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if the data is quite big let's try to
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some data to the computer first
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this is the data i am going to send
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we also need to include usbd cdc
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if dot h as the function is available in
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include string dot h also
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now in the while loop we will transmit
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the first parameter is the buffer to
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and second is the length of the data
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let's add some delay here build it and
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it flashed successfully now before
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connecting the controller
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i am going to open the devices
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and now as i connect it a new serial
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it's not showing the name that i entered
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that might be due to drivers in windows
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10 it might show for you though
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anyway the device is connected to com5
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and i will open a serial port there
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you can choose any board rate it works
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for everything pretty much
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you can see the data is being received
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by the computer every one second
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so the transmit function is working
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now let's see how to receive data from
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as i mentioned the function to receive
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data is not available globally
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so here i am defining an array of 64
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bytes to store the data into
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now i am going to give a reference of
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this variable in the cdc
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if dot c file so that we can use it here
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in the cdc receive function i am going
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to copy the data from the incoming
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here the arguments are the buffer to
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the buffer to copy from and the size of
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mem copy takes size t as the parameter
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so we need to do the conversion here
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we are ready to receive the data now
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i should use the debugger here since i
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want to see the buffer
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i have added the buffer in the live
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as you can see the transmission is
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working all right and the controller is
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transmitting every second
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when i send some data to the controller
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it gets saved in the buffer
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i will try transmitting something else
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you can see the new data but there is a
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the data is again received successfully
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if i send this smaller data again you
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see the buffer still have the data from
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the previous transmission
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to handle this situation i am going to
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clear the buffer before receiving any
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mem set can be used for it also make
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sure you clear buff too
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i have noticed that it also keeps the
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old data stored in it
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let's run the code again
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i will add the buffer again
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this time you can see the buffer only
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contains the data we are sending
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you can later parse this buffer
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according to your requirement
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since it can be accessed from the main
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file itself there shouldn't be any
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this video can be useful if you are
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or any discovery board it can save you
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the hectic of connecting the ttl device
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for transferring data using uart
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this is it for this video i hope you
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understood the process
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you can download the code from the link
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keep watching and have a nice day ahead
