OneWirePIO_RP2040

Hardware-accelerated 1-Wire & DS18B20 library for the Raspberry Pi Pico / Pico W.

All critical 1-Wire timing is offloaded to the RP2040's PIO coprocessor — zero bit-banging, zero interrupt-disabling, deterministic communication even under heavy CPU load.

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Features

• PIO-accelerated — Reset, Write, and Read are handled entirely by hardware state machines
• Jitter-free — timing is independent of CPU load, ISRs, or Wi-Fi stack activity
• RAII resource management — PIO state machines and instruction memory are automatically released on destruction
• Runtime pin switching — multiplex multiple sensors through a single PIO instance via setPin()
• CRC-8 validation — every temperature read is integrity-checked
• Configurable resolution — 9-bit (94 ms) to 12-bit (750 ms)
• Multi-scale output — Celsius, Fahrenheit, or Kelvin
• Full diagnostics — raw scratchpad access, ROM code reading, structured error states
• Minimal footprint — 27 PIO instructions, lightweight C++ classes

Hardware Requirements

Component	Description
Raspberry Pi Pico / Pico W	RP2040-based board
DS18B20	Dallas 1-Wire temperature sensor
4.7 kΩ resistor	Pull-up between data line and 3.3V

Wiring Diagram

Pico GP2 ──┬── DS18B20 DQ (Data)
           │
         4.7kΩ
           │
         3.3V

DS18B20 VDD ── 3.3V
DS18B20 GND ── GND

Installation

Arduino IDE

1. Download this repository as a .zip file
2. Go to Sketch → Include Library → Add .ZIP Library...
3. Select the downloaded file
4. Select your board: Tools → Board → Raspberry Pi Pico / Pico W

PlatformIO

Add to your platformio.ini:

[env:pico]
platform = raspberrypi
board = pico
framework = arduino
lib_deps =
    https://github.com/angeloINTJ/OneWirePIO_RP2040.git

Arduino Library Manager

Open the Arduino IDE, go to Sketch → Include Library → Manage Libraries..., search for OneWirePIO_RP2040 and click Install.

Quick Start

#include <OneWirePIO.h>
#include <DS18B20PIO.h>

OneWirePIO bus(pio0);
DS18B20PIO sensor(bus);

void setup() {
    Serial.begin(115200);
    bus.begin(2);  // GP2
}

void loop() {
    sensor.requestTemperatures(2);
    delay(sensor.getConversionDelay());

    float temp;
    if (sensor.getTemperatureValidated(2, temp)) {
        Serial.print("Temperature: ");
        Serial.print(temp, 2);
        Serial.println(" °C");
    }
    delay(2000);
}

Examples

Example	Description
BasicTemperature	Minimal read loop — start here
MultiSensor	Multiple DS18B20 on different pins with one PIO instance
DiagnosticMode	ROM code, raw scratchpad, CRC inspection
ResolutionBenchmark	Compare 9/10/11/12-bit timing and precision
TemperatureScales	Simultaneous Celsius, Fahrenheit, and Kelvin output

API Reference

OneWirePIO (Physical Layer)

OneWirePIO bus(pio0);       // or pio1
bool ok = bus.begin(pin);   // Initialize PIO + claim state machine
bus.setPin(pin);             // Switch GPIO at runtime
bus.sendReset();             // 480 µs reset pulse
bool present = bus.isSensorPresent();  // Check presence after reset
bus.writeByte(0xCC);         // Write one byte (LSB first)
uint8_t b = bus.readByte();  // Read one byte (LSB first)

DS18B20PIO (Sensor Driver)

DS18B20PIO sensor(bus);

// Temperature
sensor.requestTemperatures(pin);
delay(sensor.getConversionDelay());
float temp;
sensor.getTemperatureValidated(pin, temp, DS18B20PIO::CELSIUS);

// Resolution
sensor.setResolution(pin, DS18B20PIO::RES_9_BIT);  // 9, 10, 11, or 12

// Identification
uint8_t rom[8];
sensor.readROM(pin, rom);

// Diagnostics
uint8_t scratch[9];
float temp;
bool crcErr;
sensor.getDiagnosticData(pin, scratch, temp, crcErr);

// Error handling
DS18B20PIO::State state = sensor.getState();
char msg[64];
sensor.getLastErrorString(msg, sizeof(msg), pin);

How It Works

The RP2040 has two PIO (Programmable I/O) blocks, each with 4 state machines and 32 instruction slots. This library loads a 27-instruction program that implements the full 1-Wire physical layer in hardware:

1. Reset/Presence — 480 µs LOW pulse, then samples the bus for a device presence response
2. Write — generates precise 1/60 µs LOW pulses for logical 1/0
3. Read — pulls LOW for 1 µs, releases, and samples the bus at exactly 14 µs

The PIO clock runs at 1 MHz (1 µs/tick), derived from the system clock via a configurable divider. All timing is cycle-accurate regardless of what the ARM cores are doing.

Architecture

┌──────────────┐     ┌──────────────┐
│  DS18B20PIO  │────▶│  OneWirePIO  │
│  (Sensor)    │     │  (PHY Layer) │
│              │     │              │
│ • CRC check  │     │ • PIO mgmt   │
│ • Resolution │     │ • sendReset  │
│ • Temp scale │     │ • writeByte  │
│ • Diagnostics│     │ • readByte   │
└──────────────┘     └──────┬───────┘
                            │
                     ┌──────▼───────┐
                     │  RP2040 PIO  │
                     │  State Mach. │
                     │              │
                     │ 27-instr asm │
                     │ 1 µs/tick    │
                     └──────┬───────┘
                            │
                        GPIO pin
                            │
                       ┌────▼────┐
                       │ DS18B20 │
                       └─────────┘

Contributing

Contributions are welcome! Please read CONTRIBUTING.md before submitting a pull request.

Quick Guide

1. Fork this repository
2. Create a feature branch: git checkout -b feature/my-improvement
3. Commit your changes: git commit -m "Add: description of change"
4. Push to the branch: git push origin feature/my-improvement
5. Open a Pull Request

License

This project is licensed under the MIT License — see LICENSE for details.

Acknowledgments

• Dallas Semiconductor / Maxim Integrated for the 1-Wire protocol specification
• Raspberry Pi Foundation for the RP2040 PIO architecture
• The Arduino-Pico community for the RP2040 Arduino core

See Also

• DHT22PIO_RP2040 — PIO-accelerated DHT22 library by the same author