I've developed for my home automation project this schematic: it's quite simple, an ESP32 GPIO enable pin drives those mosfets that gives power to the LED and enable the PCA9306 EN pin, for more specific info, refer to my previous question here.

I'm not an expert in electronic engineering and design, so I need help finding some errors (if there are any) in my circuit.

As far I know, the 330 ohm pull-up resistors are so low in order to compensate the total cable capacitance (of length 30 meters).

The circuit works, but sometimes I've got I2C errors on bus, do you guys have some hints about this simple schematic?

enter image description here

  • 1
    \$\begingroup\$ Did you put some bypass/decoupling capacitors near the Vcc pins of each ic? I recommend 1uF (thought others would recommend 0.1uF) + 10 to 100 uF cap at the 5V input of the board. Also put 4.7K instead of 1K before the led. \$\endgroup\$
    – Fredled
    Mar 20, 2020 at 1:29
  • \$\begingroup\$ I've changed the resistor on led, i'll add the capacitor on the VREF1 and VREF2 pins. In any case, when i connect the PoE on the board (olimex.com/Products/IoT/ESP32/ESP32-POE/open-source-hardware) the i2c line it gets fuzzy...i don't know why...maybe because the dev board has no galvano isolation on the PoE side? \$\endgroup\$
    – VirtApp
    Mar 20, 2020 at 9:04
  • \$\begingroup\$ As you guys can see, Olimex produces the ISO version (olimex.com/Products/IoT/ESP32/ESP32-POE-ISO/…) that uses a DCDC converter, it can help me to solve those problems? \$\endgroup\$
    – VirtApp
    Mar 20, 2020 at 10:56
  • \$\begingroup\$ Check for consistent logical inputs and outputs, so that two connected outputs don't conflict with each other, causing unstability and oscillation. \$\endgroup\$
    – Fredled
    Mar 20, 2020 at 21:39


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