---
title: "Picking I2C Pull-Up Resistors (Correctly)"
description: "A long time ago, I made a video suggesting math was unnecessary to determine proper pull-up resistor values. Like most generalized statements, that suggestion is not always…"
canonical: "https://www.baldengineer.com/picking-i2c-pull-up-resistors-correctly.html"
author: "James Lewis"
date: "2024-03-07T13:22:00Z"
lastmod: "2024-04-02T21:23:47Z"
categories: ["blog","components","element14","tutorials","workbench-wednesdays","videos"]
tags: ["bus-capactiance","i2c","oscilloscope","pull-down","pull-up","resistor","serial-bus"]
---

# Picking I2C Pull-Up Resistors (Correctly)


A long time ago, I made a video suggesting math was unnecessary to determine proper pull-up resistor values. Like most generalized statements, that suggestion is not always true. For example, in data buses like I2C, speeds like 400 kHz and 1 MHz are common. At those speeds, the pull-up resistor and the bus capacitance form an RC filter that fundamentally limits the data transmission speed. Or. It limits the range of pull-up resistor values. In this Workbench Wednesdays video, I show how to estimate I2C bus capacitance, measure that capacitance, and pick pull-up resistor values.

[Full Notes on element14 community](https://community.element14.com/challenges-projects/element14-presents/workbenchwednesdays/w/documents/28424/if-and-when-do-i2c-pull-up-values-matter----workbench-wednesdays-83)