ESP32-P4 eval board: Sleep with low power, but keep touch (of screen) active

[Maximilian22]

Hi there,

I've managed so far to program an SSE client with lvgl ui, which works fine, but draws ca. 780 mA of current from a 5V source. I'd like to realize a power save mode for this, meaning the screen is dark, all peripherals are powered down _except_ the touch function of the screen, i.e. the int_tp signal from it, to be then used as a wake-up source.

Only switching off the LCD backlight leads to 270 mA, but powering down some more parts would be nice.
However, if I enter light sleep (not even deep sleep), the int_tp signal stops functioning. There is some reaction, but the pin level is 0V (instead of 3V when functioning) , with 0.2uS Spikes of 3V.

Looking at the board schematics hasn't helped me - I don't understand how I could keep the capacitive touch (interrupt) working or powered up. Would it be sufficient to keep the I2C bus running in sleep mode? Or can I somehow keep the power supply for the touch part active and it would work?

Any hints or help would be appreciated!
Thanks,
Max

[chegewara]

b) Green Mode
In Green mode, the scanning cycle for GT911 is about 40ms. It automatically enters Normal mode ifany touch is detected.
c) Gesture Mode
After the host enables GT911 to enter Gesture mode by sending I2C command 8 to 0x8046 and thento 0x8040, wake-up can be achieved by swipe, double-tap, or writing of specified letters on TP.
In Gesture mode, when GT911 detects any finger swipe on TP for a sufficiently long distance, INT will
output a pulse for longer than 250us or a high level causing the host to wake up and turn on thescreen.
In Gesture mode, when GT911 detects any double-tap on TP, INT will output a pulse for longer than250us or a high level causing the host to wake up and turn on the screen.
In Gesture mode, when GT911 detects any writing of specified letters on the TP, INT will output apulse for longer than 250us or a high level causing the host to wake up and turn on the screen.
d) Sleep Mode
GT911 enters Sleep mode if it receives corresponding I2C command from the host (requires INToutput low before the command). GT911 exits Sleep mode and enters Normal mode when hostoutputs a high level to INT pin for 2ms to 5ms. The interval between sending screen-off commandand wake-up should be longer than 58ms.

Chapter 8.1
https://www.fortec-integrated.de/filead ... asheet.pdf

[Maximilian22]

Thanks chegewara, I didn't know that!

I'm still a bit at sea: What happens, when I send the ESP32-p4 to light (or better deep) sleep with the GT911? Does it get a sleep command (i.e. variant d sleep mode) as well and needs to be waken up sperately again before I can use its int-pin to trigger a wake-up interrupt at the esp32-P4? How would I do that?
In summary I'd like to send everything to sleep _except_ the touch part, which then should be able to wake the whole system by a simple touch.

Max (-:

[chegewara]

Sorry, but this is something i didnt test yet and i dont plan to do for now.
My suggestion is to connect logic analyzer to INT pin and then make some experiments with GT911 by changing setting with I2C.
Documentation i sent above should be enough to do it.
When you see how INT pin behaves you can start fiddling with sleep modes on P4.