---
title: "The \"Minimalist Champion\" of Embedded Communication —‑ How One‑Wire Does the Most with the Least Har"
url: "https://maker.wiznet.io/ruilixin6/projects/the-minimalist-champion-of-embedded-communication--how-onewire-does-the-most-with-the-least-har/"
markdown_url: "https://maker.wiznet.io/ruilixin6/projects/the-minimalist-champion-of-embedded-communication--how-onewire-does-the-most-with-the-least-har/md"
type: "UCC: User Created Content"
author: "FreakStudio"
author_url: "https://maker.wiznet.io/ruilixin6/"
original_author: "Freakstudio"
original_url: "https://openwrite.cn/articles/63388/edit"
published: "2026-08-14"
language: "en"
tags: ["one-wire-protocol"]
likes: 0
views: 104
comments: 0
source: "WIZnet Makers (https://maker.wiznet.io/)"
---

# The "Minimalist Champion" of Embedded Communication —‑ How One‑Wire Does the Most with the Least Har

> 1-Wire is a half-duplex serial bus by Dallas Semiconductor, transmitting clock & data on one wire with parasitic power supply. It covers iButton tags, various s

Original author: Freakstudio (source: https://openwrite.cn/articles/63388/edit)

## Article

【Preliminary Note】The original hardware example in this article was written based on the RP2040. The actual hardware used in this hands-on demonstration features the W55RP20 as the main controller chip. The circuit logic and UF2 flashing operation principles are universally applicable, with only the main controller model differing. The original chip model mentioned in the circuit descriptions below is provided for reference purposes only.

![](https://mcnszeyqf1h6.feishu.cn/space/api/box/stream/download/asynccode/?code=NTRhZDNkNTk5MGQ0ZDgzYTBmOWU2ZTUwMDVlNTZmNjBfcXQycm9GdnZiTDNDeHFtdjFFVUJMdlJXemU0amxuMDlfVG9rZW46TllOb2JZSks0bzc2aUt4QjI0ZmNGUjNYbnplXzE3ODY3MDE5NTg6MTc4NjcwNTU1OF9WNA&add_watermark=true&scene_type=CCM)

### **1. Introduction to the 1-Wire Communication Protocol**

The 1-Wire bus is a wired half-duplex (cannot send and receive data at the same time) serial bus designed by Dallas Semiconductor. It can provide low-speed data communication through a single wire (typical communication rate is 16.3 kbit/s, with a maximum communication rate up to 142 kbit/s). **It uses a single signal line to transmit both the clock and bidirectional data.**

The 1-Wire bus communication is commonly used in communication scenarios between a single master and multiple slave devices, such as a microcontroller communicating with small sensor devices (for example, digital thermometers and weather instruments).

![1280X1280 (1).PNG](http://openwrite.cn/uploads/21597/63388/6179f59d-da39-46b9-9c81-03ae2ad259f1.png)

1-Wire bus communication has two notable features:

**The data line can be used to provide power.** Sensors using 1-Wire communication have a small capacitor (~800 pF) integrated inside to store charge, and this capacitor powers the device while the data line is active:

![1280X1280.PNG](http://openwrite.cn/uploads/21597/63388/302c828f-0d94-4f28-9b26-7de8eae81af7.png)

**1-Wire communication is designed for momentary contact environments.** When the host loses contact with or is disconnected from the 1-Wire device, the connected 1-Wire slave enters a reset state (such as power-off). When voltage is restored, the slave wakes up and emits a signal.

In addition, 1-Wire communication has advantages such as simple wiring, low hardware overhead, low cost, and easy bus expansion and maintenance.

### **2. History and Usage of the 1-Wire Communication Protocol**

The 1-Wire communication protocol was invented by Dallas Semiconductor in the 1980s. Its main purpose was to use chips to create computer-readable tags to replace human-readable tags, and to apply them in scenarios such as large supermarkets, warehousing, and logistics. The earliest device using the 1-Wire communication protocol was the iButton touch socket. We can view the iButton standard at the following link:

https://web.archive.org/web/20090127003835/http://www.maxim-ic.com/products/ibutton/ibuttons/standard.pdf

![1280X1280 (2).PNG](http://openwrite.cn/uploads/21597/63388/e32fef5f-d57b-47f4-9499-e5d7198729fc.png)

![1280X1280 (3).PNG](http://openwrite.cn/uploads/21597/63388/b11e2828-574b-4abe-8fe2-f3dd9d8cd010.png)

In short, the `iButton` standard is similar to today's `1-wire` protocol. The simplest structure of the `iButton` standard is a data line and a ground line, except that there are some special requirements in the circuit structure:

The ground line is made of a two-piece stainless steel container called `MicroCanTM`, which also serves as the protective shell;

The data line is a cup-shaped probe with a round surface.

![1280X1280 (4).PNG](http://openwrite.cn/uploads/21597/63388/6220c6af-dca8-47cf-80be-8c5b5e08f49d.png)

The most common device using 1-Wire communication is the iButton magnetic keyring (also known as the Dallas key). It consists of a button cell battery, an outer iron ring, a plastic keychain, and an internal circuit board. The iButton magnetic keyring needs to be used with a reader; the two communicate through the 1-Wire communication protocol to identify any iButton as a specific 48-bit ID number. iButtons can be built into rings, tags, and other personal items that can be carried on the body, for identifying specific people or items.

![a2585038-70a1-4723-a7b7-34548fb2f1c1.png](http://openwrite.cn/uploads/21597/63388/42201f1d-5ec5-4b3d-9897-43c2ad584c6a.png)

The following is a physical image of the iButton touch socket used to unlock personal computers in the 1980s:

![9396f8f5-7548-442c-b1d9-7165dccbbbfd.png](http://openwrite.cn/uploads/21597/63388/2a3138cf-943e-4880-af76-666b07112fb0.png)

In addition to the iButton standard circuit interface, 1-Wire communication devices also use traditional transistor (TO-92) and IC (TSOC, TDFN, SOT23) packages:

![3c81f2fb-8463-45f3-8e6c-c44b95310833.png](http://openwrite.cn/uploads/21597/63388/9fe142db-2bc9-4531-9f76-967f93917919.png)

Currently, the voltage levels used by 1-Wire devices can be divided into the following four types:

1.71V (min) to 1.89V (max)

1.71V (min) to 3.63V (max)

2.97V (min) to 3.63V (max)

2.8V (min) to 5.25V (max)

1-Wire devices can be classified into the following categories according to their functions:

![ScreenShot_2026-06-09_202144_400.png](http://openwrite.cn/uploads/21597/63388/0b87a707-b62c-43b4-9650-65c5d0d7d36c.png)

In addition to the above 1-Wire devices used for device ID identification, there are also many sensors in PCs that use the 1-Wire communication protocol, such as temperature recorders, timers, voltage and current sensors, battery monitors, and memories. These devices are connected to the PC through bus converters.

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Source: https://maker.wiznet.io/ruilixin6/projects/the-minimalist-champion-of-embedded-communication--how-onewire-does-the-most-with-the-least-har/