Example changes to be made to use nvs example or read write to internal flash on STM32H750B-DK

[MaazSk]

I am using STM32H750B-DK board I want to run the nvs example on it and need help regarding setting up the overlay file for the board. I am new to zephyr and unable to figure out what changes are required to make it work

[nordicjm]

NVS will not work on that device due to the sector size

[MaazSk]

@Laczen it is working flash write erase is working I'll move forward now. What I am trying now is that I won't have the partition but will write a code to write and read from internal flash. Is there a way to get the device name directly. Sorry for asking so many questions but I am new to zephyr.

[nordicjm]

@MaazSk In theory your board should be capable of supporting nvs. However your board has some peculiarities that might make it challenging to support the flash API. Your board is using a "dual" external flash setup (at least the latest in tree dts) that has received little testing. While looking at the driver I think the page-layout is not correctly reflecting the "dual" flash (@FRASTM doesn't the erase-block needs to be doubled for "dual" flash). Next to that it is also not clear where to put the flash partition layout in the dts for a "dual" flash layout. I would advice to enable the flash shell (CONFIG_FLASH_SHELL=y) and to use the shell to test the flash (find out the flash device, test erase, test write, ...). You will need to be forgiving about a possible driver error (e.g. test with erase size = 8kB instead of the expected 4kB). Test writing/erasing somewhere at a 8kB border past your image size. Once you have some basic idea that the flash is working (and you know the device name) it is possible to look at partitioning the flash.

How will this work, the sector size is 128KiB? You set a maximum size of 64KiB

[Laczen]

What you have probably been testing is the internal flash (flash0). On your device the internal flash is very limited and meant to be used for a bootloader that starts a program from external flash. Although you could use a part of the internal flash for nvs it is better to focus on trying to add storage (either nvs or later littlefs) on the external device.
Using the shell you can find out which devices are available ("device list") that should allow retrieving the external flash device name. You can then test the read/write/erase on the external flash.

[Laczen]

How will this work, the sector size is 128KiB? You set a maximum size of 64KiB

The device/development kit has (dual) external flash. The external flash will allow a erase-block of 4kB (but as both flashes are used at the same time, even data stored in external flash1 odd data in external flash2) the "real" erase block will be 8kB. The 128kB internal flash seems to be indeed only 1 "sector" so it can't really be used for anything but a bootloader.
How to setup the dts with dual flash (partitioning) is not clear to me yet.

[MaazSk]

I am still not sure how to simply write and read from internal flash is there a sample code available that can be used?
zephyr/tests/drivers/flash/stm32 passes the test but how can I use it in my code the .dts file generated in the build folder is different from other .dts file specially the flash part is there a sample code to read and write in internal flash?

[FRASTM]

For the stm32h750 , the internal flash is 128KB containing one user sector fo 128KB
this sector size = 0x20000 exceeds the uint16_t sector_size; /** Number of sectors in the file system */
of the struct nvs_fs {

The samples/subsys/nvs/ cannot run on the internal flash memory since the (single) sector used for storage also contains the code. It cannot be erased !

[MaazSk]

Okay, is there a simple read and write to internal flash sample code available? I tried zephyr/tests/drivers/flash/stm32 passes the test but how can I use it in my code Also the .dts file generated for the test has a storage_partition whereas when I run a normal code it does not have a storage_partition in it.

Is there a sample code to read and write in internal flash?

[Laczen]

@MaazSk you should not look at the internal flash, it is unusable for storage as it only has 1 (large) sector. It is the external flash that can be used for storage. The storage_parttion should be defined on the external flash. The problem is that the external flash is made up of 2 (q)spi flashes and the partition needs to be added to one/both of these to allow flash_map to retrieve the device it is working on. Your dk is the first (AFAIK) that has this dual external flash setup so it is the first to have this problem.

[MaazSk]

@Laczen Currently what I am trying and want to do the POC is just to read and write to the internal flash. I have a small amount of data say an array of 50 bytes which I want to store in the internal flash and read it whenever necessary. So, that's the reason I am focusing on reading and writing to internal flash.
Also, my next step is to have flash protection feature

[Laczen]

@Laczen Currently what I am trying and want to do the POC is just to read and write to the internal flash. I have a small amount of data say an array of 50 bytes which I want to store in the internal flash and read it whenever necessary. So, that's the reason I am focusing on reading and writing to internal flash. Also, my next step is to have flash protection feature

You can do that, but... The internal flash is only 1 sector, if your firmware is running from this location the data will be removed everytime you update your firmware. If your firmware is running from external flash you can only use this with the flash interface, but not to create "persistent" storage because whenever you need to erase the flash block it will erase everything that is there. It should be straight forward to program this with the flash api, but it will have limitations as a result of the 1 sector.

[FRASTM]

write/reading the internal flash of the stm32h750b_dk out of the code area is still possible with the samples/drivers/flash_shell/
once the sector has been erased previously (it was during the west flash), but it is like an OTP

*** Booting Zephyr OS build v3.7.0-rc1-589-g85a0440af172 ***                                                          
uart:~$ flash write flash-controller@52002000 0x1f000 0x55555555                                                      
Write OK.                                                                                                             
Verified.    

[MaazSk]

I did this and was able to write, read and erase but how to do the same using code?

[FRASTM]

I did this and was able to write, read and erase but how to do the same using code?

I suggest to build a basic application (model could be tests/drivers/flash/common) with flash_write() and flash_read() on the flash_dev device

[MaazSk]

okay will try this just give me some time

[FRASTM]

take a look a this
flash_h7.zip
west build -p always -b stm32h750b_dk samples/boards/stm32/flash_h7/

*** Booting Zephyr OS build v3.7.0-rc1-588-g40810983ead2 ***

flash-controller@52002000 STM32H7 flash testing
==========================

Test 1: check Flash erased
Flash erase succeeded!

Test 2: Flash write
Attempting to write 16 bytes
Data read matches data written. Good!!

[MaazSk]

Hi @FRASTM,
Thank you! for the code it works fine and gives me a basic idea of how to read and write.
I have a small question when I reset the device it gives me an error that it is unable to write and the error code is -5. Can you please help me why is that so? Also, I made a minor change in the code attaching the same for your reference

Test 2: Flash write
Attempting to write 16 bytes
Flash write failed! -5

flash_h7.zip

[FRASTM]

Hi @FRASTM, Thank you! for the code it works fine and gives me a basic idea of how to read and write. I have a small question when I reset the device it gives me an error that it is unable to write and the error code is -5. Can you please help me why is that so? Also, I made a minor change in the code attaching the same for your reference

Test 2: Flash write
Attempting to write 16 bytes
Flash write failed! -5

flash_h7.zip

Resetting the board does not erase the flash. It can be written only one time after erasing.
So after flashing (which erases the sector) and first run, any next run or next tentative to write (like executing this sample) will fail.
As said this flash area is more an OTP.

[MaazSk]

Hi @FRASTM,

One last thing I want to confirm so I wanted a write protection so if it is something like an OTP do I need to implement a write protect?
I was trying to add

uintptr_t code = (uintptr_t)OB_WRPSTATE_ENABLE;
	rc = flash_ex_op(flash_dev, OPTIONBYTE_WRP, code, NULL);
	if (rc != 0)
	{
		printf(" Write Protection failed with error: %d", rc);
	}

But it failed everytime and gave me an error -88
Also, I tried to change it to

uintptr_t code = (uintptr_t)OB_WRPSTATE_ENABLE;
	rc = flash_ex_op(flash_dev, OPTIONBYTE_WRP, NULL, NULL);
	if (rc != 0)
	{
		printf(" Write Protection failed with error: %d", rc);
	}

But the output was same so I wanted to confirm do I need to implement a write protect or not?
Also, what is the correct way to implement the api flash_ex_op

Thank you in advance

[Laczen]

It is only a OTP because of your usage pattern (the image and data reside in the same flash erase block). When the image is updated the data that you have written is erased. There is no need to implement some write protection, it is not allowed to rewrite an already written location. You can check if an area is erased before writing any data to it.

Although you can use this for some storage over reboot it has very limited usability. It would be good to share the intended usage so we can help in giving the right solution direction.

[FRASTM]