I2C Multiple devices Pull Up resistor

Using Arduino Networking, Protocols, and Devices
#1

Hi,
I'm making a project with Arduino UNO and some components.
I want to use an OLED I2C display and a DS3231 I2C RTC.

Is it necessary to insert the pull up resistors between the SCL / VCC and SDA / VCC pins?
If yes, what will be the value of the resistances?

Thanks in advance for your help

#2

Is it necessary to insert the pull up resistors between the SCL / VCC and SDA / VCC pins?

That is necessary but it must exist exactly once on the bus. As most breakout boards already include pull-ups you usually have to rather desolder them than to add. Because you failed to provide links to the components you use, you on your own to decide what pull-ups are needed or must be removed.

#3

If you are using this DS3231 ds3231Module.pngmodule, then the module has built-in 2x4.7k resistors on the I2C Bus. There is no need to insert external pull-ups.

The recommended values for the pull-ups of the I2C Bus are: 2.2k/4.7k/10k.

ds3231Module.png

#4

Hi,
the DS3231 that I use is this:

1000×1000 127 KB

the OLED display that I use is this:

569×569 45.3 KB

I connect the SDA/SCL pin of the oled to the A4/A5 pin of arduino and the SDA/SCL pin of the DS3231 to the other pin on the arduino SDA/SCL. I explain in more detail on the attachment.

Do you think that the circuit is ok?

UNO pins.png
UNO pins.png1599×1101 150 KB

#5

GabrieleBraconi:
Do you think that the circuit is ok?

Should be alright!

#6

Note that the SDA and SCL pins by pin 13 and ground are directly linked to the A4 and A5 pins. There is only 1 I2C bus.

#7