@felmue thanks for your message: i also had the "din base" and the "lan module" connected (but not used). disconnecting the lan module fixes the problem!!

hi

i have a weird problem with the CoreS3 SE + COMMU. i have some RS485 device and data coming on a UART configured to the CoreS3 port (next to the USB-C connector). data is displayed/updated on the screen. during (arduino) development all worked fine. flashing code over USB automatically restarts the code and i have a nice display updating every second.

but i found out that not flashing the CoreS3 and just connecting USB-C for power (and logging) i get a somewhat scrambled display.

i have chatted quite a bit with the M5Stack AI chat but it is still not fixed. everytime i just connect USB-C it is a bit scrambled. re-flashing the same code give a nice and clean display. what is going on??

my initialization code is (most of it suggested by M5Stack AI):

    auto cfg = M5.config();
    cfg.internal_imu = false;
    cfg.internal_mic = false;
    cfg.clear_display = true; // Ensure display is cleared during init

    // Initialize M5 with proper power sequencing
    M5.begin(cfg);

    // Explicitly reset the AW9523 IO expander that controls display power
    Wire.begin(11, 12); // CoreS3 internal I2C bus pins
    Wire.beginTransmission(0x58); // AW9523 address
    Wire.write(0x00); // Reset register
    Wire.write(0x00); // Perform hardware reset
    Wire.endTransmission();
    delay(100);

    // Re-initialize display with full reset
    M5.Display.init();
    M5.Display.setBrightness(128);
    M5.Display.fillScreen(TFT_BLACK);
    M5.Display.display();

the wire command actually give errors so i do not think it is doing anything:

E (3570) i2c.master: I2C transaction unexpected nack detected
E (3571) i2c.master: s_i2c_synchronous_transaction(945): I2C transaction failed
E (3572) i2c.master: i2c_master_multi_buffer_transmit(1207): I2C transaction failed

here is a "scrambled" picture:

and this after reflash:

help?!

@ajb2k3 thanks!

any idea how to do this with the M5Paper?

cheers

oh, whoa, the gps unit actually has a tiny battery in it!

so does this mean it will always "hot start"? (if it has not moved too far)

how long will this battery last?

hello

i am using the at6558 gps unit with a m5paper. i only need gps data every now and then and turn keep it turned off most of the time to save power

now i do not want to wait for cold start the gps. how can i hot start it? is there code available?

thanks
frank

gps documentation says:

Start Time: Cold start: 35 seconds, Warm start: 32 seconds, Hot start: 1 second

@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:

@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:

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

strange effects were because using the wrong way to access port.C..

this is correct:

canvas.createCanvas(960,540);

answering my own question:

#include <M5EPD.h>
#include <TinyGPS++.h>

  static const uint32_t GPSBaud = 9600;

TinyGPSPlus gps;
HardwareSerial ss(2);

M5EPD_Canvas canvas(&M5.EPD);

char latStr[10];
char lonStr[10];
char speedStr[10];

void setup() {

  M5.begin();
  M5.EPD.SetRotation(0);
  M5.EPD.Clear(true);

  ss.begin(GPSBaud, SERIAL_8N1, 19, 18);

  canvas.createCanvas(960, 540);
  canvas.setTextSize(3);
  canvas.clear();
}

void loop() {

  int b = ss.available();

  while (b > 0) {

    gps.encode(ss.read());

    double lat = gps.location.lat();
    double lon = gps.location.lng();
    double speed = gps.speed.kmph();

    dtostrf(lat, 2, 2, latStr);
    dtostrf(lon, 2, 2, lonStr);
    dtostrf(speed, 2, 2, speedStr);

    canvas.clear();
    canvas.drawString("Lat:   " + String(latStr), 50, 100);
    canvas.drawString("Lon:   " + String(lonStr), 50, 150);
    canvas.drawString("Speed: " + String(speedStr), 50, 200);
    canvas.pushCanvas(0, 0, UPDATE_MODE_DU4);
  }
}