pydigitemp 1.4.1

Python implementation of 1-Wire protocol

Python implementation of 1-Wire protocol.

Originally written to replace digitemp utility in my pet project and get direct access to 1-wire devices. It was created for reading DS1820 temperature sensor connected to RS232 serial port through DS9097 adapter.

Documentation used

• Using an UART to Implement a 1-Wire Bus Master

• Book of iButton® Standards (PDF)

• DS18S20 High-Precision 1-Wire Digital Thermometer (PDF)

Supported Hardware

Bus Drivers

• DS9097 - COM port adapter which performs RS-232C level conversion.

• Custom 1-wire serial port interface (see below).

1-Wire Devices

• DS1820 / DS18S20 / DS1920 - High-Precision Temperature Sensor.

• DS18B20 - Programmable Resolution Temperature Sensor.

• DS1822 - Econo Temperature Sensor.

Usage

Find ROM codes for all connected devices:

from digitemp.master import UART_Adapter

print(UART_Adapter('/dev/ttyS0').get_connected_ROMs())
# ['108739A80208006F', '10A75CA80208001A', '2825EA52050000CE']

Get temperature when there is only one 1-wire device on the bus:

from digitemp.master import UART_Adapter
from digitemp.device import TemperatureSensor

sensor = TemperatureSensor(UART_Adapter('/dev/ttyS0'))
sensor.info()
print(sensor.get_temperature())

Get temperature from specific sensor:

from digitemp.master import UART_Adapter
from digitemp.device import TemperatureSensor

bus = UART_Adapter('/dev/ttyS0')
sensor = TemperatureSensor(bus, rom='108739A80208006F')
sensor.info()
print(sensor.get_temperature())

You can directly instantiate a device class to use its features (e.g.: setting resolution):

from digitemp.device import DS18S20
sensor = DS18S20(bus, precise=False)

or:

from digitemp.device import DS18B20
sensor = DS18B20(bus)
sensor.set_resolution(DS18B20.RES_10_BIT)

digitemp.device module provides following device classes:

• DS18S20 - for DS1820, DS18S20 and DS1920 High-Precision Temperature Sensors (family code: 0x10);

• DS18B20 - for DS18B20 Programmable Resolution Temperature Sensors (family code: 0x28);

• DS1822 - for DS1822 Econo Temperature Sensor (family code: 0x22)

• DS1820, DS1920 - are aliases for DS18S20

See more examples in examples directory.

Schematics

IMPORTANT DISCLAIMER: All circuits presented here are collected from different sources on the Internet and thus are provided on an entirely “as-is and no guarantees” basis. We do not provide a warranty of any kind and cannot be held responsible in any manner.

1-wire serial port interface

See Serial Port Temperature Sensors - Hardware Interface for details.

USB/UART adapter

These are tested:

• ds18b20-uart.svg

• ds18b20-uart-par.svg

• ds18b20-uart-dioda.svg

• ds18b20-uart-diodapar.svg

Not all schematics work in all cases, depending on adapter and cable length.

These are not tested yet:

• ds18b20-uart-mosfet.svg

• ds18b20-uart-npn.svg

Thanks

• Slavko for SVG schematics and testing.

License

Python license. In short, you can use this product in commercial and non-commercial applications, modify it, redistribute it. A notification to the author when you use and/or modify it is welcome.

See the LICENSE file for the actual text of the license.