ESP32-S3 I2C Pullup Resistors : are they necessary ?

[Christian Hortolland]

Hello,
I have been working with ESP32-S3 for several years (T-Display Lilygo and XIAO boards) in the Arduino environment, and I have just realised that the I2C bus (which I have implemented on several different circuits: TC74, SHT21, PCF85263, DS3231, etc.) taking care to add pull-up resistors, as indicated in this documentation https://docs.espressif.com/projects/esp ... s/i2c.html, can in fact work without them (at least I was able to verify this for the TC74 and the SHT21). Would it be possible to know how? Internal resistors to the GPIOs implemented by the Wire library? Or something else...
Thank you in advance for your answer !
Christian

[Sprite]

The ESP32 has pullups, but they're too large (50K'ish) to work reliably, but it might be enough in some circumstances to just work. Also, a fair amount of boards with sensors on them have pull-ups integrated in them: technically they're generally also not enough to be in-spec, but they may work regardless as well.

[Christian Hortolland]

Thank you very much for this answer !
Best regards !