Why less current with more redraw activity?

[wired]

Doing some current consumption research.

I have a TouchGFX application running on the STM32F469I-DISCO board in portrait mode It is primarily doing just GUI activities, to simulate the GUI screens and transitions, etc. for GUI design and usability evaluation.

I have a 72-pixel high status bar at the top of the screen, and the remainder of the screen is the screen-specific stuff. My background does not overlap between the two areas.

In my status area, I have a 48x48 pixel icon fading in and out continuously. On my main screen, I have a larger image (240x250px) that is not moving until I press a GUI button on the main screen. Once I do that, using the Move Animator the image starts moving downward until it reaches its bottom point, then repeats the move from the starting position. It does this continuously until I press another button.

So, my Joulescope is indicating that my average current is 195mA when only the small image in the status bar is fading in and out, but when I start the image moving on the main screen, my average current drops to 188 mA. This doesn't seem logical to me, since I am interacting with the display more when both images need updating.

Can anyone think of possible reasons for this? Thanks for any help.

[MM..1 · Accepted solution]

Simply you dont info refresh rate / tick. I mean your fade and move is based on tick.

Situation 1 fade only cant be accelerated then every your tick need recalculate and rewrite full faded icon. Icon is small then no "dropped" not calculated frames occurs. Result more power as

Situation 2 fade plus move can overtime one refresh cycle then calculations is less often and too move can be accel D2DMA result less current.

[wired]

Thank you very much for taking the time to provide your input, MM. After I read your comment, I went to another screen where I am fading a much larger version of the symbol in and out on the main area of the screen, while simultaneously fading the small icon in the status area. The current dropped to 167 mA. Then, when I turn off the fading of the status bar icon, the current dropped further, to 166 mA. I then went to a different screen where there were no animations, and the current dropped to 160 mA. This seems to confirm your assertion that the most current is due to calculations being performed.

Also I'm curious, would you be able to confirm based on your experience that a scalable image will not draw more power than a fixed image as long as it is not being resized?