I'm Marko, electronic engineering hobbyist, who discovered esp8266 recently.
While finding my way around, I've noticed some strange behavior on a ESP-12F, that I'm not sure what causes it.
I've made a simple sketch that has wifi, simple web server, some I2C communication, real time clock with ntp update and Arduino OTA. It's kinda learning project where the code itself does nothing special, it shows a simple web page with some controls, turning a few leds through IO expander, based on user input and current time.
While doing the tests, I noticed that supply current is fluctuating from 10-20mA to 80-90mA, a few times a second. The module has an on board led, connected to GPIO2, which is turned on in the sketch. Previously mentioned oscillations are somewhat visible on this led, because it changes it's brightness in the same rhythm as the current changes noticeable on the power supply.
The first thing I've done when troubleshooting the issue was multi stage bypassing of power supply, as it seemed obvious, since the test circuit is on the breadboard. This had no effect on the fluctuations.
The next thing I did was to remove parts of the code and libraries from the sketch, one by one, suspecting that this comes from software. I ended up with nothing but the bare minimum for turning GPIO2 low. This, also, had no effect.
The next thing was to remove all components from the circuit, but a few jumpers for basic configuring of esp module. No effect, as you may already predict.
The last thing I did is uploading MicroPython on the module. I've made it connect to wifi and put GPIO2 to low, which is kind of similar state as in my previous tests. The module consumes constant 75mA with MicroPython and no fluctuations are noticeable, not in current measurement, nor in led brightness change.
I didn't test with another module, since all I have come from the same source (ultra cheap ones from Aliexpress - could this be the cause?).
It came to my mind that some settings in IDE could be the problem, but I've tried altering the ones I understand, with no success. IDE is 1.6.13.
Do you have any idea what could be the cause?
Thank you!