First of all my background is chemistry so please be kind when I ask a (probably) dumb question. In my retirement I have started to tinker with electronics hence the query ..

I have googled around but can't find any information

I2C circuit for the DS3231 clock I am building from an SO8 package should have a pull-up of 10K for each channel which would give an overall resistance of 5K as they are in parallel, OK so far.

Could a use only one resistor of 4.7K connected to both channels instead ?

Thank you in advance for any help of explanations you can give

 

Hi C,
Use just two 4k7's as per this image.
E

 

Could a use only one resistor of 4.7K connected to both channels instead ?

NO

 

One 10kΩ pull-up will do. You don’t need two in parallel.

 

Just so you don't get confused...The entire bus line gets a pullup, not every device on the bus. So, one pullup for the SCL line and one for the SDA line. Values as given above, and are not critical...4.7K will work as will 10K.

 

Thanks for the replies of those who took the time to explain things. I realise that if I only tried to use one resistor SCL and SDA would have to be directly connected to each other before the pull up which would be very bad.

 

Just to clarify that you understand, SCL and SDA are not considered to be two channels.
To avoid confusion, let us not use the word "channel".

Look at this drawing from post #5 posted by @upand_at_them.



Here is an example of multiple devices (or slaves) in an I2C system. In this case three devices are shown.
SCL and SDA each have their own pull-up resistors. There is only one pull-up resistor for SCL and one for SDA for the entire system.

The value of the pull-up resistor can be 10kΩ. This value is not critical for the proper operation of I2C.