M5Stack Atom Lite: Long response times and wifi connection losses

  • My M5Stack Atom Lite had very long http server response times and strange wifi connection losses. Sometimes it happened after week, sometimes already after hours.
    I did a lot of research in the internet until I found the following post (under https://github.com/espressif/arduino-esp32/issues/2144):
    In this schematic you can see, that there is a resistor missing which causes far too high voltage on the pins GPIO0 and EN.
    Although this schematic does not belong to the M5Stack-Atom, I made a try by reducing the input power by 0.7 V to 4.3 V (by inserting a silicium diode in the V+ path) on my module. So the voltage of GPIO0 and EN is still too high but inside the specification.
    And I was successful: With this correction, my module works without problems since about three weeks now!
    Unfortunately, I could not find any schematic of Atom or Atom-Lite to verify.

    Does anyone know anything about this problem? And does anyone have a schematic of the Atom or Atom-Lite?

    Btw: I installed a counter into the idle loop and found, that the ESP32 made about 1000 calls to the idle loop per second before my correction and about 3000 to 5000 after. My ESP8266 with the same software (but without an operating system) does about 30000 calls per second!

  • Hello @RolfF

    interesting information. Thank you for sharing. A bit further down in the thread you linked user sohtamei claims: This issue has been found in M5Atom/M5StickC/TimerCAM/unitV, and we fixed it with FW update of CH552. If that is true, then I guess your M5Atom must be rather old or did not get this update for some reason.

    And no, afaik there is no full schematic for the M5Atom Lite or Matrix, just the sketchy one here.


  • Hello @RolfF

    It's a design mistake.
    It is a basic mistake to add 5V to 3.3V system.
    5V enters the RF circuit, causing deterioration or damage.
    There are many cases where ATOM has already broken.
    M5Stack Community
    Short Wifi effective range and IO0=3.9V issue with Lite and Matrix : About a year ago
    M5Stack Community
    New CH552 firmware for Short-Wifi-Issue of M5Atom/Stick/TimerCAM/etc. : About 9 months ago
    Bugs and measures for M5Stack ATOM : 2021.10.10
    How to not change FW.
    Other measures : Low the voltage of GPIO_0.
    The voltage on GPIO_0 decreases and the transmit power increases.