ESP8266 Community Forum

- Sun Apr 10, 2016 5:40 pm #45259 Hey everyone,

I got a very mysterious problem with mit NodeMCU V1.0 and Arduino Mega 2560.
I've connected both like this:


A short description about the basically logic software on each controller:

NodeMCU:

Turns on a digital output, if I got a HTTP request - works very solid and well

Arduino:

Checks in a loop function, if a digital input from the NodeMCU to the Arduino is logically high.
If so, it opens a short function.



Now my problem description:

When I power both devices, the logic level of the in the sketch defined NodeMCU Outputs are high just for a second.
After that, everything works well.

If I press the reset button on the NodeMCU, or if I switch the power supply for the NodeMCU, I got all defined Inputs on the Arduino logically high. If I turn on the power supply for the NodeMCU, all defined Outputs are logically high.

Now my very simple question:
- What can I do against this circumstances?

Best regards,

Julian

- Mon Apr 11, 2016 8:14 am #45279 That is pretty normal !
When ESP is in reset state, the GPIOs are floating, which is almost equivalent to HIGH level state.
To prevent that affecting your software, you should probably assume that Idle state for all those GPIOs are HIGH, and driving those to LOW when you wish to send the even. In other words, reverse are the logics.