Noise when interacting with i2c

[dynek=]

Hello everyone,

I know this is super light, but before digging too much into it, I wanted to check if there's something obvious and known about ESP32 and i2c.

Got a GPIO (17) on an ESP32 wroom that is set to PWM 50% duty and here's what I see with the scope:

SDS00034.png (18.96 KiB) Viewed 4356 times

Now when there's an interaction on the i2c bus (RTC, ADC, LCD screen) here's what it becomes:

SDS00035.png (31.38 KiB) Viewed 4356 times

How can I get rid / lower that noise? I'm using GPIO 22 & 23 for i2c.

Any hint will be appreciated!

[dynek=]

No one noticed this before?

[ESP_Sprite]

It honestly looks like something caused by the way you measure things... it looks like the signal you get goes above Vcc and below Gnd, and the ESP32 is not capable of generating those voltages.

EDIT: No, I'm reading it wrong. Your original signal already is odd, as it has an amplitude of less than a volt and floats way above ground. Are you sure there isn't a break in your design somewhere and the signal is simply lightly capacitively coupling to your probe?

[dynek=]

It's A 2N3907 being driven high-side: https://www.eevblog.com/forum/beginners ... e-voltage/

[ESP_Sprite]

If you're wondering if the ESP32 is generating that noise, better to measure it before the base resistor. (Also note that the noise seems to be pretty high-freq; making sure your oscilloscope ground doesn't make a big loop will probably also help to get an accurate measurement.)

[andrea05256]

You should check the Grounds .... the whole circuit should have a common ground

and the circuit's ground should be common with the ground of the oscilloscope ....

[dynek=]

You are right, one of the ground cable was guilty for this, replaced it and it's ok now

Thank you