how to let screen off with STM32MP15X-EVAL

Spaik.1 · ‎2021-07-16

Hi,

The display is always on with the eval-board. I would like to know how to let it off.

Kernel Version : openstlinux-5.10-dunfell-mp1-21-03-31

Best Regards,

Sun

PatrickF · ‎2021-07-19

Hi,

I assume you talk about backlight control ?

#turn off backlight
echo 0 > /sys/class/backlight/panel-backlight/brightness
#turn on backlight
echo 1 > /sys/class/backlight/panel-backlight/brightness

Note that this does not stop the display itself (LTDC/DSI) nor it's power (which are directly from VIN 5V and STPMIC1 Buck4 3V3).

Regards.

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Spaik.1 · ‎2021-07-19

Hi,

Can I turn off the display itself and power as well?

Best Regards,

Sun

PatrickF · ‎2021-07-19

I don't think it is possible to shutdown the display supply.

VIN 5V is always ON and 3V3 supply is shared with other platform components.

Could you share the goal to get the display in power down?

Notice that if you don't use the display, you could simply remove it from the board.

EV1 is not optimized for power, but rather defined to provided as many interface flexibility as possible for MPU STM32MP15 Series evaluation purposes.

Maybe you could do some HW hack on this board or wait to use your own HW.

For stop display (LTDC/DSI), you probably have to remove the related definition in board Device Tree. See https://wiki.st.com/stm32mpu/wiki/Main_Page

Regards.

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Spaik.1 · ‎2021-07-20

Hi,

Thank you for your warm support.

Actually, I would like to know how to set the board to low power mode. I thought the board does not go to low power mode because the display is always on. That's why I asked it. Please let me know how to address it if you knew it.

Best Regards,

Sun

PatrickF · ‎2021-07-20

Hi,

Maybe have a look to AN5284, (note that this AN was using old ecosystem SW, so Linux commands might have evolved, as well as power results which has sometimes been optimized on latest Ecosystem).

I repeat that EV1 board is not optimized for good power consumption, so values in AN5284 does not reflect best you can get.

To get rid of many platform components of the MotherBoard, you might try to use the EV1 MB1263 Daughter Board in standalone (you could use UART console thru STLINK with some jumper settings). Obviously, this limit the scope to SD-Card or eMMC flash, no USB, no display, no ethernet, no audio, etc...

For a quick idea of STM32MP15 power (product datasheet remain the main source of data), see https://wiki.st.com/stm32mpu/wiki/How_to_define_your_low-power_strategy#Overview.

Then to estimate your platform overall power, you should add power of external components (in low-power modes, usually only the DDR3L or LPDDR2/3 in Self-Refresh are needed), not forgetting to take into account platform power supplies efficiencies (LDO quiescent or SMPS efficiency).

Regards.

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PatrickF · ‎2021-07-20

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