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Interface WS2812 LEDs with STM32 || SPI 8bit
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Sep 9, 2023
Purchase the Products shown in this video from :: https://controllerstech.store ________________________________________________________________________________________ Original Article :::: https://www.newinnovations.nl/post/controlling-ws2812-and-ws2812b-using-only-stm32-spi/ STM32 Playlist :::: https://www.youtube.com/playlist?list=PLfIJKC1ud8gga7xeUUJ-bRUbeChfTOOBd DOWNLOAD THIS PROJECT FROM :::: https://controllerstech.com/ws2812-leds-using-spi/ ________________________________________________________________________________________ ******* SUPPORT US BY DONATING****** https://paypal.me/controllertech *******Join the Membership******* https://www.youtube.com/channel/UCkdqtSMnhYuMsJkyHOxiPZQ/join Join the Discord Server https://discord.gg/D32JE5wKyD Join the Telegram Group https://t.me/controllerstechdiscuss
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0:01
[Music]
0:08
hello and welcome to controllers Tech
0:12
few months ago I made a video covering
0:15
ws2812 addressable LEDs
0:18
we used the timer pwm with dma to send
0:22
the data to the LEDs
0:24
that video is still one of the most
0:26
appreciated videos I ever uploaded
0:29
while many of you made it work using
0:32
that method some of you still had
0:34
problems with it
0:35
while for some the dma Callback wasn't
0:38
being called for others one or two LEDs
0:41
were behaving inappropriately
0:43
today we will cover yet another method
0:45
of interfacing these addressable LEDs
0:49
instead of pwm we will use the SBI
0:53
we can achieve High board rates with SBI
0:55
and therefore we can match the bit
0:57
timing required for the LEDs
1:00
here is the original article that I took
1:03
the reference from
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you can read this I will leave the link
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in the description
1:09
here is the data sheet of the
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ws2812 addressable LED driver
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we will directly jumped to the timing
1:17
section
1:18
here are the big timings for zero and
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one
1:22
to send a zero we need to keep the
1:24
signal high for 0.35 microseconds and
1:28
then low for 0.8 microseconds
1:31
and to Sender one we need to keep it
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high for 0.7 microseconds and low for
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0.6 microseconds
1:40
the timing is flexible and an error of
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150 nanoseconds is acceptable here
1:46
the total time for a pulse should be
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around 1.25 microseconds with an error
1:52
of 600 nanoseconds
1:54
we will use the SBI peripheral with the
1:57
board rate of 2.5 megabits per second
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this means that each bit will be
2:03
transferred in 0.4 microseconds
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if we want to transfer a zero we can
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send a 1 followed by two zero bits
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we know that each bit is equivalent to
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0.4 microseconds so this bit sequence
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will keep the signal high for 0.4
2:22
microseconds and then low for 0.8
2:25
microseconds
2:29
this is exactly what the requirement is
2:32
the
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ws2812 driver will see these three bits
2:37
as a single zero bit
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similarly to Sender one we will send two
2:42
one bits followed by a zero bit
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this will keep the signal high for 0.8
2:48
microseconds and then low for 0.4
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microseconds
2:53
this is not the exact but an acceptable
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timing for the one
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the
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ws2812 driver will see these three bits
3:02
as a single one bit
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the period for the three bits is 1.2
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microseconds which is as per the
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requirement in the data sheet
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we will discuss more things in this data
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sheet later let's first open the IDE and
3:20
create a new project
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I am using the
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f446re controller
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give some name to the project and click
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finish
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let's start with the clock
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bypass the clock as it is provided by
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the St link itself
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the board has 8 megahertz Crystal and I
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am running it as the maximum possible
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180 megahertz clock
3:47
now go to the connectivity and enable
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the SPI in half duplex mode
3:53
we only need to send the data so half
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duplex mode is fine for us
3:58
let's keep the data size as 8 Bits as we
4:01
only need to send three bits
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the data should be transferred as MSB
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first
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now we need to bring the board rate to
4:10
2.5 megabits per second
4:13
this setup doesn't allow me to do that
4:16
let me reduce the main clock to 160
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megahertz
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all right here we have the 2.5 megabits
4:25
make sure the clock polarity is low and
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the clock phase is one Edge
4:30
this is basically the SPI mode 0. two
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pins got selected for the half duplex
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mode
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we have the pin pa5 as the clock and the
4:41
pin pa7 as the data pin
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we will connect the PIN pa7 to the LED
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input
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this is all the setup we need click save
4:51
to generate the project
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we will create separate Library files
4:56
for the LED driver
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so create
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aws2812 header file in the include
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directory and see file in the source
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directory
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let's start writing the code in the
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source file
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include the main file and the
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ws2812 header file also
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Define the number of LEDs being used
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also Define an array to store the color
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data here I am defining a matrix array
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which will store the three colors for
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the respective LED
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let's write a function to set the colors
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for the respective LED
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the parameters of this function are the
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LED number the red color code the green
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code and the blue code
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these color codes should be in the RGB
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format
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here we will store the LED number in the
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first element of The Matrix
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then store the green color in the second
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element the red in the third and the
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blue in the fourth I am storing the
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green color first this is because as per
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the datasheet the green color byte is
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the most significant byte then we have
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the red and at last the blue
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therefore it will be easier to extract
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the data later in the code
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now let's write another function to send
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the data through the SPI
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the parameters are the color codes
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here we will first combine the three
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color bytes and make a single 24-bit
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color data
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in the beginning we discussed that each
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color bit will be equivalent of three
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SBI bits
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we will store these three SPI bits in a
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single byte element
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since there are 24 color bits in total
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let's create an array of 24 bytes
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also Define an index variable to keep
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track of how many bytes have been
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occupied in the array
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now we will assign the SBI bits for each
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color bit and store them in the array
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we have to send the MSB first therefore
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the extraction should start from the
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most significant position of the color
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data
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we will first shift the color data by 23
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places to the right and extract the bit
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at that position
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if the bit is a 1 we will store 1 1 0 in
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the first element of the array
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otherwise if the bit is a zero we will
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store 1 0 0 in the array
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then the color data will be shifted by
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22 places and we will extract the second
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bit from the end
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once all the bits from the color data
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have been extracted we will send the
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array to the SBI
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you can use interrupt dma or the normal
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mode to send this data it should work
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fine with all the methods
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we need to define the SPI Handler as an
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external variable
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let's write one more function which we
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will call from the main file to send the
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data to the LEDs
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here we will call the for loop as many
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times as the number of LEDs we have and
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each time we will send the data to the
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respective LED
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the LED data array ensures that the
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previous data for the LEDs is saved and
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if a single LED is updated it doesn't
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affect the rest of them
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every time we update even a single LED
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we have to send the data for all the
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LEDs
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also note that unlike what we did during
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the pwm tutorial here we are sending the
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data for individual LEDs
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this structure also reduces the memory
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requirement for the data array and hence
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the code can be used on the lower end
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microcontrollers also
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all right let's define these functions
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in the
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ws2812 header file
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we will Define the set LED function and
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the send function
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let's write the main file now
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include the
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ws2812 header file
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in the main function we will set all the
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LEDs to zero to make sure they are off
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in the while loop let's set all of them
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to red and send the data to the LEDs
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give a delay of one second
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Now set all LEDs to green and send the
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data
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let's build and debug the code
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here you can see all the LEDs showing
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three colors after every one second
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let me add a break point here
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all right we have hit the break point
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let's step over the send function
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you can see all the leads are red
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let's put breakpoints after every send
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function
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all the LEDs are green now
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and now they are blue
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so the code is working fine
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I have already covered this topic where
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we sent the data using the pwm
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you can simply search for
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ws2812 on the website and you can find
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it easily
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this code also has the brightness
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feature which you can Implement in the
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similar manner
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anyway I will include the brightness in
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the final code before I upload it on the
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website
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one more thing we don't necessarily need
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to set all the LEDs every time
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but we do need to send the data for all
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the LEDs
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this is how the data gets shifted the
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first 24 bits are used by the first led
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then the rest of the data is shifted to
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the next LED
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this process goes as long as there is
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data remaining
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to indicate that the data is finished we
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need to pull the data line low for more
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than 50 microseconds
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we haven't implemented this part yet
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so after the data has been sent to all
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the LEDs let's give a delay of one
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millisecond
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to display some random color we can use
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the RGB color code
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let me copy the RGB code of this color
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and now I am setting the LED 0 with this
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code
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after setting the old send the data to
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the driver
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let's comment out this part
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let's build and run this now
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here you can see the LED shows the same
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color
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it might not be accurately visible in
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the camera
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here first we set all the LEDs to off
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and then display single color on the LED
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zero
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let's set another color now
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I am setting this to the LED one
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let's build and run this now
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here you can see both the colors are
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being shown on the LED zero and led1
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respectively
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so we were able to send the data to the
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LEDs using the SBI
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I hope you understood the process
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I will add the brightness to the library
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before uploading it
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the details will be updated in the
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article as well
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this is it for today
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you can download the code from the link
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in the description
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leave comments in case of any doubt
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keep watching and have a nice day ahead
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