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Cache memory seems to crash?

Associate III



I am creating a scrollable list of items, and we want have an image for each one of the items in the list, I have created a code that always prints 12 images depending on the scrollContainer.getScrolledY() value. This is for memory saving.


To display the image i use BMPFileLoader.cpp from the touchGFX documentation.

And i have created a 6MB cache in FrontedAplication.cpp which can print my image like 21 times.(I use the same image for debugging but later on they will have different images)

This is how I update the images:


I call lthis code every 50 ticks.

And everything works perfectly but once a amount of ticks has passed, this is what happens to the images:


They dissappear, and i don't know what is causing this. I'd like to debug or be able to see whats being stored in the cache or if clearCache() is really removing the images from the cache, but I have no way to do this right?


As I said before, this happens after an amount of ticks have happened as if i call this every 5 ticks for example, the crash happens much faster.




Accepted Solutions
ST Employee

Hello @I_ve_got_a_problem ,


@JTP1 have mentioned to me that you are not closing your file after reading it.
I have tried to close it in the project you sent and it does solve the problem for me.
All I did was adding 


at the end of your createBitmap function.


I the solves your issue, I invite you to select this message as "best solution".



Gaetan Godart
Software engineer at ST (TouchGFX)

View solution in original post



to check , cache doing something here or not , simple way: disable (not enable) D-cache at all.

Then you see : cache problem or your code (memory overflow, ..etc.) has a problem.

(maybe then also wrong cache management..).

If you feel a post has answered your question, please click "Accept as Solution".

This is a simulator project so i don't really know how I can enable or disable D-Cache, but until I declared this in the FrontedAplication.cpp the images wouldn't show, so it must be storing them in this cache:


Also if I try to print all of them i only see like 20-22 of the images, and if i reduce the cache declared in there it does show less images, so it's storing them there


Oo, so i got it wrong. (I was thinking : real cache in a complex cpu ...)

You have a "cache" memory area, to buffer the images - right ?

So you have to free some memory, not overflow the area.

Or limit what you put in, to the available size of 6MB - or what you can use.

If you feel a post has answered your question, please click "Accept as Solution".

Yeah but how do I do that, i thought the clearCache function would do that, but it looks like it's not doing anything.

Here is some data i collected:

      If I execute updateList() every 50 ticks, it takes 36 segs to crash

      If I execute updateList() every 25 ticks, it takes 18 secs

Both this tests were done with 3MB declared in frontedAplication.cpp

      I tried the once every 25 ticks test but with 6MB and it crashed in 18 seconds too.

There is some concept that i'm missing here, because this suggests that the memory assigned in frontedAplication.cpp isn't doing anything at all, but if i coment whats inside it, no image appears, at all, which says that somehow it's storing them there in the first place.

And same with the function clearCache() it seems that it's not doing anything, but if dont call it where I do in the updateList() function (image from my first post) it takes only 1 sec to crash.

ST Employee

Hello @I_ve_got_a_problem ,


What board are you using? Did you select a board when creating the TouchGFX project in Designer or did you select simulator?


Try to isolate the issue. 


Try to import your GUI into a simulator project, see if the issue still happens and share the project here.


You can disable cache in the ioc file (STM32CubeMX) here :

I assumes you were using a H735 as you said you used this MCU in previous posts.

Do you ever get into your catch?
What does populateList do?


What have you tried debugging?
Put a print at the end of your try to see if you finished everything you want to.
Print the address of the bitmap you are copying from so you know if you are getting out range without an error (and therefore copying only zeros).


You issue doesn't seems to be linked to the size of your virtual cache because when increasing it you still get 18 seconds.


With your measured timings, it seems you enter your functions 43,2 times, so probably 43 or 42 times).


Try to print your bitmap ID without scrolling, you should get the same IDs since you don't change what you display.


What does "createBitmap" does? It seems to be a function that you created.


Please share a picture of the project before it stops displaying so we know what it should look like.



Gaetan Godart
Software engineer at ST (TouchGFX)


All these was done in the simulator so far. 

The createBitmap function just creates a dynamic bitmap and then returns its id.


If i print the bitmapId's i can see that it creates and deletes the 12 images in every loop, basically it prints bitmap ids from 58 to 70, and when it crashes it displays bitmapId: 65535 which if i'm not wrong is just the bitmap invalid id.


When its working we can just see the images that we are telling it to load to the ram on runtime



Yesterday I tried adding 100 images to the cache on a separate function that is not a loop, and only draw the 12 images on the screen using the loop and it wouldnt crash(this is not a good solution for us, we want to only have 12 images in ram in every time). So it must be something related to the create bitmap action. I do Bitmap::clearCache() in every tick but i dont know if this is really reseting the cache, or if the images are leaving some leftover that ends up overflowing the cache, even though that wouldnt make much sense as the size of the cache I set doesnt affect the time it takes it to crash.



ST Employee

Hello @I_ve_got_a_problem ,


Since this is only a simulator project, can you share it so I can see it all?



Gaetan Godart
Software engineer at ST (TouchGFX)

Hi sorry for not replying faster

I have isolated the problem in a new project and exported the custom container to it so you can see, the behaviour of the problem is exactly the same as in my main project, 

I don't know if it's a problem with my code, or that your approach on how to cache images is not suitable for my case in which i need to load and delete images infinetly so that we can add images on runtime but always only having 12 or so in the ram.


I have attatched the project below.

Hello @I_ve_got_a_problem ,


No problem!

I have looked at your shared project.
The 43th call is having a problem, the 5 first image load work but the 6th fails.
I have tried updating only 6 images (inside updateList) at a time and by doing this, I was able to call the function 84 times successfully but fail at the 85th call.
So the 509th read always fails.

I figured that the size of the 509 call was wrong (value width and height in the getBMP24Dimensions function).
By manually changing those values to the pixel size of your image (240 x 240) I am not encountering any error anymore.

	width = 240;
	height = 240;

This is just a quick walk around that would work if all of your images are the same size.



Gaetan Godart
Software engineer at ST (TouchGFX)