I2C pull-ups for ESP32 devkit + DS3231 module

franck102
Posts: 8
Joined: Thu Mar 12, 2020 5:45 pm

I2C pull-ups for ESP32 devkit + DS3231 module

Postby franck102 » Wed Mar 25, 2020 3:48 pm

Hi all,

I am working on a project that will combine an ESP32 devkit rev 1 and a DS3231 module like this one.

I would appreciate it if you could comment on my current thinking w.r.t pull-up resistors for the I2C SDA & SCL lines:
- the Wire library will enable the internal pullups on the ESP32, that's about 10K
- the module itself has additional 10K pullups on each line (I'll check once I receive it)
- I will add an additional 10k pull-up per line

This should result in 3.3K pull-ups per line, which should work well for that bus (3.3V, single I2C device, short lines).

Any thoughts?
Thanks!
Franck

boarchuz
Posts: 204
Joined: Tue Aug 21, 2018 5:28 am

Re: I2C pull-ups for ESP32 devkit + DS3231 module

Postby boarchuz » Wed Mar 25, 2020 4:19 pm

Internals are not 10k, they're about 50k.
That still leaves you with <5k, which will be fine. If you have any issues you can always lower the I2C speed.

franck102
Posts: 8
Joined: Thu Mar 12, 2020 5:45 pm

Re: I2C pull-ups for ESP32 devkit + DS3231 module

Postby franck102 » Thu Mar 26, 2020 8:37 am

Thanks for the feedback!

Franck

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