# How is the I2C bus arranged? Part 6

How can we determine the value of the resistors Rs and Rpu?

There is the answer to this question in the original documentation. The diagrams that optimize the method of selecting the resistors are given there. The diagrams are normalized with respect to the different supply voltages, but as the option of using chips with Vdd = 5 V is considered the most likely to be used, the information is limited to this voltage only.

First we choose the Rpu resistor. We can make conclusion that the stray capacitance has practically no influence on the methodology of the choice of the resistor. You also may ask the following question: How to determine the value of the stray capacitance? Indeed, it is not so easy to do that. Modern computer circuit simulation packages during wiring of printed circuit boards allow us to model stray elements and determine their value. However, such programs are not available to everyone, and not everyone is able to use them properly. So while developing amateur designs you need to adhere to the "golden mean" and take on a value of the stray capacitance of no more than 100 - 200 pF.

Having determined the Rpu, let’s define the face value of the Rs resistor (if it is supposed to be put into the circuit). In the end we check the face value of the Rpu resistor. For example, it must be not less than 1.5-2 kOhm for the supply voltage of 5 V.

Meeting the requirements of the diagram will enable the maximum information rate in Hs-mode.