B4R Library rOneWireEx

rwblinn · Aug 26, 2026

B4R Library rOneWireEx

Brief
rOneWireEx is an open-source library wrapper for the Dallas/Maxim 1-Wire protocol, specifically optimized to fix strict execution timing and macro definition conflicts on the ESP32 platform.

Purpose

Provides a dependable 1-Wire hardware communication layer for ESP32 and AVR microcontrollers.
Solves the "all zeros" hardware discovery issue by bypassing internal framework timing lag.
Allows dynamic resolution tuning (9-bit to 12-bit) to drastically reduce sensor conversion wait cycles.

Development Info
This B4R library is:

A OneWire library wrapper with additional functions.
Written in C++ using Arduino IDE 2.3.10 and the B4Rh2xml parsing tool.
Depends on the platform (minimum version) [email protected], Arduino UNO R4 Boards 1.6.0 and the native OneWire library 2.3.8.
Tested with ESP-WROOM-32 (32-bit, 3V3 logic), Arduino UNO R4 (32-bit Renesas RA4M1 architecture, 5V logic).
Tested with B4R 4.00 (64-bit).

Test Setup
Arduino UNO R4, DS1820b Sensor High Temperature.

Compatibility

Supports boards based on both AVR and ESP32 architectures.

Files
The rOneWireEx.zip archive contains the compiled library assets and usage examples.

Install
Copy the rOneWireEx library folder from the ZIP into your B4R Additional Libraries folder, keeping the directory structure intact.
Ensure the core underlying OneWire library is installed using your Arduino IDE libraries manager first.
Several example in the folder examples.

Functions

Initialize (WirePin As Byte)
Initializes the bus object. Sets the physical 1-Wire signal pin assignment.
ReadAddress (Address() As Byte) As Boolean
Scans the OneWire bus for the next available device address. Writes the unique 8-byte ROM address directly to the provided array. Returns True if a device is successfully found.
Example output: 28330A9497040373 (28 = Family code for DS18B20, 330A94970403 = Unique hardware serial number, 73 = CRC validation byte).
ResetSearch
Clears the internal library search state. The next call to ReadAddress will start scanning from the beginning of the bus.
ReadTemperature (Address() As Byte) As Float
Performs a full real-time reading block (Reset, Select, Convert, Delay, Read Scratchpad). Automatically auto-senses the active sensor resolution settings dynamically to optimize performance. Returns calculated Celsius value. Returns -127.0 if transmission fails or CRC checks drop.
SetResolution (Address() As Byte, ResolutionBits As Byte) As Boolean
Sets the operational resolution of a specific sensor (Accepted values: 9, 10, 11, 12). Updates internal non-volatile EEPROM registers.
Reset As Boolean
Performs a global hardware bus reset function. Returns True if a device on the line asserted a valid presence pulse.
Select (Address() As Byte)
Issues a direct hardware select command. Required to address a specific sensor after each bus Reset call.
Skip
Skips the long device selection loop process. Highly useful to accelerate data fetching when only a single sensor is wired to the bus pin.
Write (Value As Byte, Power As Boolean)
Writes a single command byte directly to the bus. Set Power to True if parasitic power is required immediately following the transmission.
WriteBytes (Bytes() As Byte, Power As Boolean)
Writes an entire array sequence to the bus.
ReadBytes (Bytes() As Byte, Count As UInt)
Reads raw data from the active bus sensor and populates it directly into the target buffer array up to the specified Count.
CRC8 (Data() As Byte, Length As Byte) As Byte
Computes a standard Dallas Semiconductor 8-bit cyclic redundancy check.
GetDeviceType (Address() As Byte) As Byte
Identifies the device type numerical category from its 8-byte ROM address.
- 1 = DS18B20
- 2 = DS18S20
- 3 = DS1822
- 4 = MAX31820
- 0 = Unknown / Other Hardware Profile
GetDeviceTypeName (Address() As Byte) As String
Identifies the human-readable device model name directly from its 8-byte ROM address. Returns a memory-safe string allocated on the B4R internal memory frame stack.
- 0x28 = "DS18B20"
- 0x10 = "DS18S20OLD"
- 0x22 = "DS1822"
- 0x3B = "MAX31820"
- 0x01 = "iButton Key"
- 0x24 = "EEPROM Storage"
- Other = "UNKNOWN"

Constants

RESOLUTION_9 As Byte = 9 (DS18B20 9-bit resolution profile)
RESOLUTION_10 As Byte = 10 (DS18B20 10-bit resolution profile)
RESOLUTION_11 As Byte = 11 (DS18B20 11-bit resolution profile)
RESOLUTION_12 As Byte = 12 (DS18B20 12-bit resolution profile)

Example

Code:

Sub Process_Globals
    Private VERSION As String = "rOneWireEx Basic v20260826"
    ' Communication
    Public Serial1 As Serial
    ' Sensor Bus
    Private WireBus As OneWireEx
    Private BUS_PIN As Byte = 4
    Private Address(8) As Byte
    ' Helper Tool
    Private bc As ByteConverter
End Sub

Private Sub AppStart
    Serial1.Initialize(115200)
    Log(CRLF, "[AppStart] ", VERSION)
    ' Init onewire bus pin
    WireBus.Initialize(BUS_PIN)
    ' Search and read the connected device 64-bit address
    WireBus.ResetSearch
    If WireBus.ReadAddress(Address) Then
        Log("[AppStart] address=", bc.HexFromBytes(Address), " type=", WireBus.GetDeviceTypeName(Address))
        ' Expected log: [AppStart] address=28330A9497040373 type=DS18B20
    End If
End Sub

Troubleshooting

Pull-Up Resistor: The DS18B20 requires a 4.7 kΩ resistor connected between the Data line (Pin 4) and VCC (3.3V or 5V). Without this physical hardware pull-up, the data line cannot pull high, and communication or discovery fails completely returning all zeros.
Ensure your specified pin variable declaration matches the physical hardware GPIO map layout of your target AVR or ESP32 module manufacturer specifications.
Always issue a call to ResetSearch before starting a brand new multi-device iteration search loop sequence.

License
MIT License - see LICENSE file.

Credits

Developers & maintainers of the native Arduino OneWire library.

Disclaimer

All product names, logos, and brands are property of their respective owners.

B4R Library rOneWireEx

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