1-Wire Protocol Commands

Overview

• Bus: 1-Wire
• Connections: one pin (OWD) and ground
• Output type: open drain/open collector
• Pull-up resistors: always required (2K - 10K ohms)
• Maximum voltage: 5volts

1-Wire is a common bus for low speed interfaces.

Configuration options

• None

Pull-up resistors

1-Wire is an open-collector bus, it requires pull-up resistors to hold the data line high and create the data '1'. 1-Wire parts don't output high, they only pull low, without pull-up resistors there can never be a '1'.

Enable the Bus Pirate onboard pull-up resistors with the P command.

tip

• 1-Wire requires a pull-up resistor to hold the data line high.
• 1-Wire parts don't output high, they only pull low.
• Without pull-up resistors there can never be a '1'.
• Enable the Bus Pirate onboard pull-up resistors with the P command.

Syntax

Command	Description
{ or [	Issue 1-Wire reset, detect device presence.
r	Read one byte. (r:1…255 for bulk reads)
0b	Write this binary value. Format is 0b00000000 for a byte, but partial bytes are also fine: 0b1001.
0x	Write this HEX value. Format is 0x01. Partial bytes are fine: 0xA. A-F can be lower-case or capital letters.
0-255	Write this decimal value. Any number not preceded by 0x or 0b is interpreted as a decimal value.
space	Value delimiter. Use a space to separate numbers. No delimiter is required between non-number values: {0xa6 0 0 16 5 0b111 0xaF rrrr}.
(#)	Run macro, (0) for macro list.

Macro

Number	Description
0	Macro menu
1	1-Wire ROM search. Find all connected device IDs.
2	Read temperature from a single 18B20 sensor.

1-Wire ROM search macro

Bus Pirate [/dev/ttyS0]

1-WIRE> (1)
1-Wire ROM search:
1: 28 5c aa 13 0a 00 00 19
1-WIRE>

Macro (1) performs a 1-Wire ROM search to detect the ID of every connected 1-Wire device. They type of device is shown if the family ID is known.

Read 18B20 temperature

Bus Pirate [/dev/ttyS0]

1-WIRE> (2)
RX: 1a 01 00 00 7f ff 06 10 12 Temperature: 17.625
1-WIRE>

Macro (2) reads the temperature from a single 18B20 temperature sensor. The macro uses the skip ROM command, so it will only work when the DS18B20 is the only device connected.

Connections

Bus Pirate	Direction	Circuit	Description
OWD	↔	OWD	1-Wire Data
GND	⏚	GND	Signal Ground