ESP32 + OLED sd1306 different behaviour USB power vs direct power

odaller
Posts: 1
Joined: Sun Apr 14, 2019 6:31 pm

ESP32 + OLED sd1306 different behaviour USB power vs direct power

Postby odaller » Sun Apr 14, 2019 6:37 pm

Hello,

I encounter the weirdest problem: with my H-ET LIVE MiniKit ESP combined with "1.54 inch SSD1309 OLED Display Module 128x64 I2C Interface OLED 3.3-5V Compatible With SSD1306"

I use I2C communication and the SSD1306 library.

When I power my ESP module with an USB cable from a wall adapter, the screen starts without problems and everything seems to work fine.
However, when I power the ESP module directly with 5v into the VCC pin, the screen only shows random pixels. The esp boots up fine, since i can still reach the webpage it provides.

Anyone ideas how to fix this?

Thanks

PCNDATA
Posts: 1
Joined: Wed Apr 24, 2019 12:30 pm

Re: ESP32 + OLED sd1306 different behaviour USB power vs direct power

Postby PCNDATA » Thu Apr 25, 2019 12:00 am

When you power from USB, then your CP2102 USB-Serial converter will hold RST line active for a longer time than when directly powered.
Directly power with +5V at your (WeMos) module do not have that option (because no signal change at USB d+ and d-).
You can overcome this with an external RST (or circuit :) ).

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