DS18B20 temperature sensor

[dchappel]

@sk

onewire.py and ds18x20.py are in my lib directory (available here per @LoneTech: http://donkey.vernier.se/~yann/onewire.zip)

This works for me:

import time
from machine import Pin
from ds18x20 import DS18X20

while True:
    
    d=DS18X20(Pin('P23', mode=Pin.OUT))
    
    result=(d.read_temps())
    
    if result:
        val=str(result[0]*1.8+32)
    else:
        val="-1"
        
    print(val)
    
    time.sleep(5)

[DonHugo]

@dchappel i cant get this to work, i get

# code block
Running 
Traceback (most recent call last):
  File "<stdin>", line 7, in <module>
  File "ds18x20.py", line 47, in __init__
  File "onewire.py", line 246, in scan
  File "onewire.py", line 269, in _search
  File "onewire.py", line 90, in reset
OSError: OneWire pin didn't go high
>
MicroPython v1.8.6-464-g0f843911 on 2017-02-17; LoPy with ESP32
Type "help()" for more information.

what firmware are you using?

[dchappel]

@DonHugo

(sysname='LoPy', nodename='LoPy', release='1.5.1.b1', version='v1.8.6-423-g18444a2 on 2017-02-07', machine='LoPy with ESP32', lorawan='1.0.0')

The pin not going high message sounds more like a wiring issue? Are you sure your wiring is correct and the pullup resistor bridges +3.3V and data? I had same issue and realized that I had sensor wire colors mixed up...

[Guizmolux]

@dchappel
I'm very new to this (and LoPy and python) : where is your lib directory ?(I'll adapt to my own config).

[livius]

@Guizmolux
I do not know if you ask for this
but fully working examlpe code you can find in official docs
https://docs.pycom.io/pycom_esp32/pycom_esp32/tutorial/includes/onewire.html

[Guizmolux]

@livius
I get that. Copied the code into a onewire.py file. Where should I put it?
I've tried to execute before the main.py file and I always get the "cannot import name OneWire" or "DS18X20".
is the const() a problem in class OneWire ?

[livius]

@Guizmolux

but do you have upgraded firmware?
current is 1.6.12.b1
what is yours? you can check firmware version by

os.uname()

if it is really old then go to
https://www.pycom.io/resources/

next, is this how your onewire looks like?
https://github.com/pycom/pycom-libraries/blob/master/lib/onewire/onewire.py

put it in the same place where you have main.py or in lib subfolder

and then you can simply use it

import time
from machine import Pin
from onewire import DS18X20
from onewire import OneWire

#DS18B20 data line connected to pin P10
ow = OneWire(Pin('P10'))
temp = DS18X20(ow)

while True:
    print(temp.read_temp_async())
    time.sleep(1)
    temp.start_convertion()
    time.sleep(1)

[Guizmolux]

@livius
it didn't seem to work with Pymakr. The Atom IDE with Pymakr pluggin solution that was updated as a tutorial last week definitely helped.
It seems to be good now.
Thank you!

[soren]

@livius said in DS18B20 temperature sensor:

https://github.com/pycom/pycom-libraries/blob/master/lib/onewire/onewire.py

When I do exactly as you state here, and connect the temperature sensor to 3.3v, and with the 4,7k resistor between sig and 3.3v - I get this error:

File "main.py", line 22, in <module>
File "/flash/lib/onewire.py", line 190, in read_temp_async
IndexError: list index out of range

I have latest firmware and atom plugin

EDIT: after checking that I have latest onewire from here https://github.com/pycom/pycom-libraries/blob/master/lib/onewire/onewire.py this error was gone. I then had to correct your spelling mistake in "convertion" and now it's working, but despite everything being hooked up correctly - it prints out "None"...

[livius]

@soren

1. what you got from (you must change P10 to pin you use):

ow = OneWire(Pin('P10'))
ow.roms

if nothing then test(double ow)

ow.ow.scan()

2. which sensor do you have exactly? woterproof or some different?

[jimpower]

@dchappel I followed your main.py with both onewire.py and ds18x20.py in my lib, this works for the first temp reading, every following temp reading doesn't change from the first. I moved the sensor into the fridge and then freezer and the readings styed the same. Once I reset the device it will bring the new reading but only again for the first reading. Did you find this with yours?

[livius]

@jimpower
better look here
https://github.com/pycom/pycom-libraries/tree/master/examples/DS18X20

[jimpower]

@livius thanks that did the trick