Control backlight from GPIO

[jemarro12]

I´d like to turn off G9CA01 based LCD display with ESP32 GPIO. i´d like to switch on/off display with GPIO, don't know if better turn off only backlight or if better turn off all vcc line. Attach Schematic of display. Wich kind of transistor should i use for the job? Consumption about 50mA at 3.3V
In addition i´m using powerboost 1000C as battery charger which provides LBO pin (normally at BAT level and when BAT<3V LBO pulled to GND). I´d like to detect this LBO pulled to GND in a GPIO. Maybe compare LBO pin (adapted to be 3.3vmax) with VCC/2 V??

[jpanhalt]

Turning off the backlight (BL) will save almost all of the current drain and will not require going through re-initialization like turning off VCC will require.  I control the BL with a moderate frequency PWM and a small, logic-level mosfet driven by a GPIO pin.  I just use 3 levels.  You can still read the display in decent light.

[Shonky]

Just turn off backlight. Rest of the LCD won't use much power. I would suggest that the 10k pull up to 3v3 be switched to a pull down to ground if anything. Do you really want the back light on by default when the unit starts before your ESP32 enables the output? As is it will also not pull the transistor base to 0V. With your GPIO low you'll still see about 0.3V on the base.

As for detecting the LBO pin you should understand what kind of output it is. If open collector a simple pull up on an input GPIO could be enough.

[DavidAlfa]

Also send "turn off" cmd to the lcd, so it enters deep sleep while keeping the configuration and framebuffer data.