#Define Callback:
def on_wasPressed(p):
print("Button was pressed: ", p)
B_M5 = Pin(37, Pin.IN, handler=on_wasPressed, trigger=Pin.IRQ_FALLING, debounce= 500)

from machine import Pin
btna = Pin(37, Pin.IN)

Perfekt, thanks a lot! Thats exactly the piece of code which I needed now.
For the link: Thats also very helpful. I didn't took the time to port the complete AXP192 library and just added the commands I needed. I will use his full port. Additionally I have to check his port because of some LCD issues I have.

from machine import Pin
btna = Pin(37, Pin.IN)
btnb = Pin(39, Pin.IN)

#for a simple test we can use the button to turn on the led on pin 10

ledpin = Pin(10, Pin.OUT)

while True:
       if btna.value() == 1:
             ledpin.value(1)
       else:
             ledpin.value(0)

hope this helps

@forestrupicolous If you use UIFlow firmware 1.4.3 then the screen works fine however it is built on a slightly older version of Micropython.

Hi @ajb2k3, is the source code available somewhere? I wasn't able to find the code for the M5StickC anywhere on github. The only UIFlow code I was able to find (https://github.com/m5stack/UIFlow-Code) has gotten it's last commit in June and I think is missing the M5StickC libraries.

Here is my prototype code to enable the display and backlight. Please be aware that I haven't included everything from the cpp file so some functionality is missing:

from machine import I2C
i2c = I2C(freq=400000, sda=21, scl=22) #Enable I2C
i2c.scan()  #Check for devices
    [52, 81, 104] #52 is the adress of AXP192

i2c.writeto_mem(52, 0x28, b'\xcc') #Set TFT and TFT_LED to 3.0V
i2c.readfrom_mem(52, 0x12, 1) #Read Byte 12
  #returns  b'\x13' = 0b10011 -> DCDC enabled but LDO3/2 disabled
i2c.writeto_mem(52, 0x12, b'\x1f') # enable LDO3/2 (TFT and TFT_LED)

# other code parts:
i2c.writeto_mem(52, 0x12, b'\x13') #disable LDO3/2 (TFT and TFT_LED)
i2c.writeto_mem(52, 0x28, b'\x9c') #Dimm display by reducing the voltage

One important thing is that the register 0x12 is also responsible for powering the ESP32. Thats the reason why just setting the LDO3/2 bits alone isn't enough.