lowest power m5paper?

[frank_b]

hello

m5paper's display does not need power to keep displaying... i only want to update the info on screen every so often (e.g. every 10s)

i am using the light sleep right now:

gpio_hold_en((gpio_num_t)M5EPD_MAIN_PWR_PIN);
esp_sleep_enable_timer_wakeup(10 * 1000000);
esp_light_sleep_start();

i read somewhere that the power to the screen can be disabled with M5.disableEPDPower(). that seems to work but how do you get i back on? there is M5.enableEPDPower() but that doesnot seem to be enough?

also: i have a gps attached and i see that that is still powered. is there a way to power down port.C?

any other things that can be powered down?

when this all works and is still nog good enough i will try to store state in eeprom and actually power down...

thanks
frank

[felmue]

Hello @frank_b

Re enable power to the screen: what do you mean M5.enableEPDPower() isn't enough?

Re Groove ports: you can only turn off all three ports together. Try M5.disableEXTPower().

BTW: Only fully powering down M5Paper will give you lowest power. At the time I did some measurements. You can find them here.

Thanks
Felix

[frank_b]

@felmue said in lowest power m5paper?:

M5.disableEXTPower()

hi felix,

turning off external power works. great!

about turning back on the screen, please see code and screen pictures below. without M5.disableEPDPower() and M5.enableEPDPower() it all works nicely. with turning on/off the screen i do see sort of that it is running but the screen does not "work" properly - i.e. i do not see the number increasing. (and "the noise" is getting worse over time). what am i doing wrong?

thanks
frank

#include <M5EPD.h>
#include <EEPROM.h>

// m5paper
M5EPD_Canvas canvas(&M5.EPD);


int count;
int boot;

void setup() {
  
  M5.begin();

  M5.EPD.SetRotation(0);

  // cleanig the screen by alternating all pixels set, all pixels reset
  M5.EPD.Clear(true);

  // use rtc
  M5.RTC.begin();

  canvas.createCanvas(960, 540);
  canvas.setTextSize(8);

  canvas.clear();
  canvas.drawString("Sleep Test...", 50, 50);
  canvas.pushCanvas(0, 0, UPDATE_MODE_DU4);

  delay(1000);

  EEPROM.begin(10);
  boot = EEPROM.read(0);
  boot++;
  EEPROM.write(0,boot);
  EEPROM.commit();

  count = 0;
}

void loop() {

  canvas.clear();
  char printBuffer[64];
  sprintf(printBuffer, "b=%d, c=%d",boot, count);
  canvas.drawString(printBuffer, 50, 50);
  canvas.pushCanvas(0, 0, UPDATE_MODE_DU4);

  count++;

  delay(1000);

  gpio_hold_en((gpio_num_t)M5EPD_MAIN_PWR_PIN);
  esp_sleep_enable_timer_wakeup(5 * 1000000);
  
  // turn off power to screen
  // M5.disableEPDPower();
  // turn off power to ports
  M5.disableEXTPower();

  // sleeps, wakesup and continues
  esp_light_sleep_start(); 

  // sleeps, wakesup and restarts
  // esp_deep_sleep_start();

  // shutsdown
  // M5.shutdown(5);

  // turn on power to screen
  // M5.enableEPDPower();
  // turn on power to ports
  M5.disableEXTPower();
}

without turning off/on power to screen:

with turning off/on power to screen:

[felmue]

Hello @frank_b

please find an explanation here. (It's for M5CoreInk, but I think the same thing is happening here.)

Thanks
Felix

[frank_b]

@felmue: nice!

just added a redraw of the screen and it all works:

  // turn on power to screen
  M5.enableEPDPower();
  // redraw screen
  canvas.pushCanvas(0, 0, UPDATE_MODE_DU4);
  // turn on power to ports
  M5.enableEXTPower();

the screen does get a bit of greyish line pattern over time:

[ajb2k3]

@frank_b normally with EInk you have to make a HV write to set the ink on the screen then you can switch the device off while still keeping the image or text on screen. If you do a normal write then the content will fade or just vanish when powered off.

[frank_b]

@ajb2k3 thanks!

any idea how to do this with the M5Paper?

cheers