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hello everyone welcome to controllers
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Tech many of you guys requested this so
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today we will see how to program the
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flash memory in stm32 this video only
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cover those microcontrollers whose
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memory is organized in pages for example
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cortex m3 series or m0 series I will
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make another video about the controllers
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whose memory is distributed in sectors
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like in cortex m4 or m7 devices I am
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and it's a medium density controller as
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mentioned here there is not much to do
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in the setup I am enabling the external
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crystal and setting the clock to run at
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save this to generate the code here is
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our main file let's include the library
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first put the C file in source directory
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and header file in the include
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include the flash page dot H in the main
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let's take a look at the reference
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is a medium density device
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as you can see the main memory is
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divided into 128 pages each page is one
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kilobyte and have a range of addresses
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associated with it now we are going to
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program this page you should always
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start as lower in the memory as possible
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I will tell you the reason for choosing
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this later in the code itself let's open
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the see file that we included flash
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write data will write the data to the
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memory it takes the start page address
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as the parameter and also appointed a
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32-bit variable that you want to store
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first of all it will calculate how many
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32-bit variables you want to write then
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it will calculate the number of pages
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needed to store the data flash page size
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varies according to the controller in my
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case it is 1024 bytes like it said in
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the datasheet after calculating the
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number of pages it will erase that many
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pages starting from the start page
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entered in the parameter now it will
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start writing data each word takes 4
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bytes so we have to increment the
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address by 4 you can also write in half
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word or double word but then the
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increment will also change I have
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commented it out here and finally the
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flash will be locked again
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to read the data we just need to access
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the memory the data will be saved in
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this variable let's start now I will
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write the data first the memory location
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that I copied from the data sheet I need
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to define this variable first Here I am
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defining an array which can hold two
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32-bit variables and we will pass the
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address of this array to the flash right
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let's build this there is some warning
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it's fine let's go ahead and debug the
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here is the memory tab let's enter the
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memory address that we want to observe
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you can see it's all clean here I also
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want to show you another memory address
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this is the start of flash memory for
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f103 controller and you can see it's not
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empty that's why I did not program the
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start of flash memory it is already
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programmed to run this code that we are
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using right now I will explain this in a
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while that what happens if we try to
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overwrite this part of the flash
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you can see it's occupied up to this
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address and therefore we should only
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program after this part that's why I
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chose the lowest part of the flash
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memory let's run this now we hit the
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break point note that the memory
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location is empty right now now let's
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step over this and you can see the data
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being stored in the flash memory other
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than in writing the 32-bit numbers we
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can also write some string to this
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memory we will write hello world in the
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let's build and debug this
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you can see right now the previous data
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is stored in the memory and as we run
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this function the data corresponding to
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hello world is stored in the flash
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I am creating another variable to store
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the data that is read from the memory
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this variable can hold forwards we will
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read from the same memory address
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I am putting our X data in the live
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we can see the data here let's see if it
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is the same data our X data is in the
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integer format so we need to select the
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same here and yes we have the same data
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present in the memory and in our X data
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now I will show you what happens when we
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try to write from the beginning in the
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flash memory I will try to write the
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same data that is hello world
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let's open the disassembly tap here you
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can see the instructions are being
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stored in the same address that we want
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to program with hello world let's enter
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inside this function I will put another
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breakpoint at the arrays function let's
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enter inside the arrays function I am
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stepping over now just to show you guys
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where the problem occurs
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now once we call this function the
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entire page will be erased and all the
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instructions will be arrays DeLonge with
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and that's where the error occurs as the
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instruction that was supposed to execute
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is not present in the memory you can see
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the memory details here this entire page
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is erased the next instruction that was
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supposed to execute was present in that
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page and is not there anymore that's why
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I advised in the beginning that we
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shouldn't write first few pages next I
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will show you how to use st-link utility
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to see the memory details
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see this the beginning of the flash
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memory is again occupied by the
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instructions we will go to the address
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that we have programmed you can see the
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hello world written to the location this
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is it guys in the final code I will
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include a function to convert the
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received data into the string format you
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can download the code from the link in
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the description keep watching be safe
