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Topic: I2C Multiple devices Pull Up resistor (Read 247 times) previous topic - next topic

GabrieleBraconi

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

pylon

Quote
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.

GolamMostafa

#2
Jun 26, 2019, 02:40 pm Last Edit: Jun 26, 2019, 02:44 pm by GolamMostafa
If you are using this DS3231 module, 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.

GabrieleBraconi

Hi,
the DS3231 that I use is this:


the OLED display that I use is this:


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?

 

GolamMostafa


groundFungus

#5
Jun 26, 2019, 05:24 pm Last Edit: Jun 26, 2019, 05:24 pm by groundFungus
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.

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