ESP32 GeekWom board I2c not square and wrong freq: Picture

Olfox59
Posts: 11
Joined: Tue May 02, 2017 12:36 pm

ESP32 GeekWom board I2c not square and wrong freq: Picture

Postby Olfox59 » Thu Dec 28, 2017 1:42 pm

Hi every body,

I'm developping an app with i2c device, and i am really surprised to see my signal really not square, it is like there is a capacitor effect on the ligne.

I also don't understand why signal frequency equal around 73khz, while i set 100khz.

I am connecting on pin 19 for scl and pin18 for sda, internal pull enabled.

I have the same waveform without conneting device and disable ACK.

Look at this picture :) :

Image

Image


Thanks for your help :)

Dig Kleppe
Posts: 24
Joined: Wed Jun 28, 2017 5:03 pm

Re: ESP32 GeekWom board I2c not square and wrong freq: Picture

Postby Dig Kleppe » Thu Dec 28, 2017 5:59 pm

Hi,
You need pullups 2k2 to 10k on both I2C lines. internal pullups are to weak.
Dont know what causes the frequency deviation.
Dig

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