M5StickC: turn off screen completely



  • @dda Thanks! @ricardocosta can probably check to see how much current is used when backlight is off.



  • While I'm at it, an explanation about M5.Axp.ScreenBreath(x);. The code is:

    void AXP192::ScreenBreath(uint8_t brightness) {
      Wire1.beginTransmission(0x34);
      Wire1.write(0x28);
      Wire1.write(((brightness & 0x0f) << 4)); //Enable LDO2&LDO3, LED&TFT 3.3V
      Wire1.endTransmission();
    }
    

    What it does is it takes the value you passed, cuts it to 4 bits (0-15) and moves those 4 bits to bits 4-7. Register 28H is voltage control for LDO2 (bits 4-7) and LDO3 (bits 0-3). So the OLED is connected to LDO2.

    What that 0-15 value represents is a voltage of 1.8 to 3.3V, in 100mV/steps. So M5.Axp.ScreenBreath(0); sets voltage to 1.8V, and M5.Axp.ScreenBreath(15); to 3.3V. Not what we really want – as the goal was to set voltage to zero... :-)

    0_1564416322717_e7e8bf46-cea3-41c2-bed7-1869e4cb9146-image.png

    Whereas register 12H controls the state (ON/OFF) of a bunch of wires, including LDO2 (bit 2). Hence the code above.

    0_1564416423649_0222b6b2-3ed3-473a-9669-0020509cb215-image.png



  • Does your code cut the voltage to the backlight only? or to the screen as well?



  • To be tested but I think this turns off OLED_VDD, ie the current to the OLED. Register 10H is said to be for OLED_VPP so setting it to zero could help too.



  • I did a simple test: with only REG 28H the screen stays slightly warm. With both 28H and 10H, the screen cools off after a while. Hardly a scientific test, I know, but seems to point to the need to set both registers.



  • @dda what a wonderful work you have done! I hope this will enable @Multihelix to use M5StickC as a watch (turn off OLED after a timeout and turn on OLED on button press or accelerometer)



  • @multihelix

    How are you getting 5 hours of life? it seems you would need <16 ma total drain

    Are you sleeping the ESP32?



  • @ws1088 Funny enough I bought my M5StickC with the watch strap and all, but not because I wanted a watch – I don't wear them – but because it enables me to tie it up to my backpack when I do LoRa range tests :-)



  • @dda said in M5StickC: turn off screen completely:

    @ws1088 Funny enough I bought my M5StickC with the watch strap and all, but not because I wanted a watch – I don't wear them – but because it enables me to tie it up to my backpack when I do LoRa range tests :-)

    why would you use m5stickc to do LoRa range tests? You can get LoRa chip with OLED screen. Do you connect m5stickc to a LoRa chip via I2C? or WiFi AP?



  • I have a lot of different LoRa chips and setups. I have one board, at 230 MHz, that I can connect through the hat connector (I need 3 pins + Vcc/GND). I have transceivers, both at 230 and 433 MHz, I connect to via RS485 (I bought a hat for that, and also some RS485 for my M5Stack cores). etc etc. The smaller the better :-)



  • @maxstack - Yes, I used ESP DeepSleep set to wake on Button A being pressed, but I would say that the 5 hour time was not under ideal conditions, as I occasionally woke up the device to confirm it was still working and to check the time - a resonable activity for a watch.



  • @multihelix Can you post a link to your watch code?



  • @dda said in M5StickC: turn off screen completely:

    I did a simple test: with only REG 28H the screen stays slightly warm. With both 28H and 10H, the screen cools off after a while. Hardly a scientific test, I know, but seems to point to the need to set both registers.

    I'm looking at this thread to hopefully implement a complete screen turn off, but am not sure what register mask to use (based on quoted post)

    Here is what I have, the screen is off but hard to know if the screen has actually been disabled.

    void turnOffScreen() {
    Wire1.beginTransmission(0x34);
    Wire1.write(0x10);
    Wire1.write(0b00000000); // 7-3=? | 2=EXTEN | 1=? | 0=DC-DC2
    Wire1.endTransmission();

    Wire1.begin(21, 22);
    Wire1.beginTransmission(0x34);
    Wire1.write(0x12);
    Wire1.write(0b01001011); // 7=? | 6=EXTEN | 5=? | 4=DC-DC2 | 3=LDO3 | 2=LDO2 | 1=DC-DC3 | 0=DC-DC1
    Wire1.endTransmission();

    Wire1.beginTransmission(0x34);
    Wire1.write(0x28);
    Wire1.write(0b00001111); // 7-4=LDO2 | 3-0=LDO3
    Wire1.endTransmission();
    }



  • @klimbot: I think you have to turn LDO3 and LDO2 off, in your code only LDO2 is off. Take a look at this picture: https://docs.m5stack.com/assets/img/product_pics/core/minicore/m5stickc/m5stickc_05.webp