M5Stack CoreS3 SE + COMMU display problem when replugging USB

frank_b

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?!

felmue

Hello @frank_b

have you tired without COMMU module stacked?

Thanks
Felix

frank_b

@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!!