OneWire has not been implemented

[bartvstratum]

There was already a similar issue posted here, but unfortunately the "solution" was a bit vague (in my opinion...).

Following the documentation on PyPi I installed OneWire with:

pip3 install adafruit-circuitpython-onewire

On a Raspberry Pi Zero. Running the example code from that page:

import board
from adafruit_onewire.bus import OneWireBus
ow_bus = OneWireBus(board.D2)
devices = ow_bus.scan()
for d in devices:
    print("ROM={}\tFamily=0x{:02x}".format(d.rom, d.family_code))

results in:

pi@meteo-pi-bvs:~/meteo/pimeteo $ python3 test.py 
Traceback (most recent call last):
  File "test.py", line 15, in <module>
    ow_bus = OneWireBus(board.D2)
  File "/home/pi/.local/lib/python3.7/site-packages/adafruit_onewire/bus.py", line 79, in __init__
    self._ow = busio.OneWire(pin)
  File "/home/pi/.local/lib/python3.7/site-packages/busio.py", line 431, in __init__
    raise NotImplementedError("OneWire has not been implemented")
NotImplementedError: OneWire has not been implemented

I really don't understand the "yah! we dont support onewire thru blinka - you can use the sysfs 1-wire library system instead (we have no way to access 1-wire data outside the kernel)" posted in the previous issue. According to the documentation, this should work on a Raspberry Pi. Then why doesn't it work?

[ladyada]

there is no low level interface for 1 wire on linux/raspberry pi like there is for uart/i2c/spi/i2s..., so you must use the kernel level 1-wire interfaces.

@dherrada wanna update that readme to remove the raspberry pi details?

[evaherrada]

@ladyada Sure

[evaherrada]

@ladyada Ok, just removed the 'Installing from PyPI' section

[ladyada]

alight hopefully that will help. perhaps one day there will be a kernel module that lets us 1wire in userspace :)

[Arthur-66]

The current Circuitpython guide for DS18B20 still indiretly suggests the DS18B20 and Onewire can be used on the Raspberry Pi:

• The OneWire page here https://github.com/adafruit/Adafruit_CircuitPython_DS18X20 which says " ...On supported GNU/Linux systems like the Raspberry Pi, ..." and indirectly on:
• https://github.com/adafruit/Adafruit_CircuitPython_OneWire which does not state that it does not make sense to install onewire on the RPi to support the DS18B20.
  I spent quite a bit of time trying to figure out what was wrong, before coming accross this thread (doesn't show up in the early pages in DuckDuckGo). Maybe it is a good idea to just put clear warnings on each of the pages that this guide and these drivers cannot be used on the PRi?

[ladyada]

@dherrada please update! ^

[evaherrada]

@ladyada On it!

[evaherrada]

adafruit/Adafruit_CircuitPython_DS18X20#21

[Bluscream]

Oh no
WHy doesn't the library implement reading the files then :c

[ladyada]

because its not a low enough interface. the kernel simply does not expose 'onewire' it only exposes 'complete ds18b20 driver'