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hello everyone welcome to controllers
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tech today in this video we will see how
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to use USB mass-storage class with or
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without using SD card let's start by
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creating the project in cube ide i am
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using stm32f4 0 7 z ii give some name to
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the project and click finish here is our
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cube MX first of all i am enabling the
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external crystal for the clock now go to
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USB OTG FS and select device only in the
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USB device select the Mass Storage class
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you can change the device descriptor
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here in this first half I am going to
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show how to use mass storage without SD
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card and that's why I am not selecting
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SDIO go to the clock configuration now I
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have 8 megahertz crystal and I want the
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system to run at full 168 megahertz
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note that this 48 megahertz clock is
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also selected this is basically the
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clock for USB click Save to generate the
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project open USB D storage if dot C file
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this is the file where we are going to
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let me first build this project
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as you can see here the device of 123
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kilobytes of free RAM and I am going to
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use this RAM as the storage let's start
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then change the storage block number to
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twice the amount of RAM that you are
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going to use I want to use 100 kilobytes
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of this Ram now create a buffer which
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can hold this 100 kilobytes of data
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storage block size is 512 and that's
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make this buffer 100 kilobytes in size
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next in the storage reach function we
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will copy the data from our assigned
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same thing in the storage right function
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but this time copying will be the other
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let's build and debug this code let's
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run this as you can see there is no
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external drive here now I will connect
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the USB to the SDM 32 it's asking to
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format the disk so let's do that
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you can see here the size is 100
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this is our mass storage disk of 100
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we can create a file write data and save
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now I will remove the USB and connect it
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back and you can see the file is still
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available but this is not always true
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sometimes it asked me to format the disk
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again I am still working on how to solve
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this issue also see here that the RAM is
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almost full as we are using it as mass
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storage now I will show you how to use
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SD card as a mass storage let's go back
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to the cube M X leave USB configuration
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and select SD i/o 4-bit mode as you can
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see here these are the pins used for SD
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this is how the pins are connected to
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this is the time a diagram for stm32f4
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as you can see the SDIO is connected to
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and the APB two is running at eighty
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four megahertz now if you remembered the
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USB full-speed clock is twelve megahertz
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so we need to bring SDIO to the same
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as mentioned here SDIO CK is equal to
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the SDIO clock divided by divided factor
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plus 2 a PD clock is 84 megahertz so we
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need to divide it by 7 for the SDIO to
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become 12 therefore the divide factor
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will be 5 that's all for the setup now
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save to generate the project
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delete the USB D storage if dot C file
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and copy this USB storage file at the
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same position this file contains the
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functions needed for SD card to work
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I am commenting out the ramp related
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functions this function will get the
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this will be used to read the SD card
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and this one will be used to write the
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let's build this note that the RAM is
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again you can see there is no external
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storage right now when I connect the USB
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the SD card is detected as the mass
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storage device the card is one gigabyte
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in size these are some contents
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I was testing with initially I will copy
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this folder now let's see how much time
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you can see this is only two point three
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megabytes folder I have removed the USB
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when connected back you can see the
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files are still present this sums up
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everything for this video you can use
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the mass storage with or without sdcard
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speed is slow right now but I will work
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on it maybe DMA can make it a bit faster
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I will update you guys if there are any
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changes made in the code in future you
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can download the code from the link in
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the description stay safe and good bye
