Pico W Micro Python for SHT30 Temp/Humidity HELP!

RP2040 based microcontroller boards running MicroPython.
Target audience: MicroPython users with an RP2040 boards.
This does not include conventional Linux-based Raspberry Pi boards.
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Roberthh
Posts: 3667
Joined: Sat May 09, 2015 4:13 pm
Location: Rhineland, Europe

Re: Pico W Micro Python for SHT30 Temp/Humidity HELP!

Post by Roberthh » Tue Nov 08, 2022 9:28 am

Semicocolon separates multiple Python statement on a singel line. A semicolon at the end of a line is simply ignored.

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crc ^= b
is the short form of

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crc = crc ^ b
These short forms are allowed for all standard operators like + - * / & | ^

This line is part of the crc calculation and should be fine.

Rissy
Posts: 116
Joined: Sun Aug 14, 2022 8:15 am

Re: Pico W Micro Python for SHT30 Temp/Humidity HELP!

Post by Rissy » Tue Nov 08, 2022 1:10 pm

Hi Roberthh! been a while!

Thanks for that information.

So there should be no harm in removing the instances of ";", or leaving them there. (I'll try removing them)

So what should i put in place of the suggested issue areas of this library file for:

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self.i2c.start()
and

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self.i2c.stop()
?

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Roberthh
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Joined: Sat May 09, 2015 4:13 pm
Location: Rhineland, Europe

Re: Pico W Micro Python for SHT30 Temp/Humidity HELP!

Post by Roberthh » Tue Nov 08, 2022 2:50 pm

Just remove them. They are not needed any more.

Rissy
Posts: 116
Joined: Sun Aug 14, 2022 8:15 am

Re: Pico W Micro Python for SHT30 Temp/Humidity HELP!

Post by Rissy » Tue Nov 08, 2022 5:12 pm

Roberthh wrote:
Tue Nov 08, 2022 2:50 pm
Just remove them. They are not needed any more.
Ok thanks.

I'll try this tonight and report back.

I want to try and get the SHT30 to receive a soft reset when it gets an error (I suspect it's a bus error) instead of right now relying on the watchdog timer i'm using to reboot the whole Pico w when it crashes.

The sensor works fine most of the time. I only seem to have an issue with it periodically when it rains a lot outside. Something with adverse weather conditions causes the sensor to do something bad and this has been crashing my code. I'd come home to find it in that crashed condition which means i am losing data as it hasn't been recording into my database the whole time due to this.

This is what i'm trying to combat against.

I've taken the I2C frequency all the way down to 5000Hz, and i'm trying to log the SHT error to a .txt log file as evidence of the fault (which i'm still guessing at based on me getting the same error if I try to ground down the cable shield to earth).

It would be nice if I could code it to recover from this bad situation without having to have the watchdog reboot the Pico W to do it.

Rissy
Posts: 116
Joined: Sun Aug 14, 2022 8:15 am

Re: Pico W Micro Python for SHT30 Temp/Humidity HELP!

Post by Rissy » Tue Nov 08, 2022 7:05 pm

I'm home, and at Thonny, and it's now I discover the plot thickens!

It seems I already have an edited version of the library file we're discussing. I'm not sure now where I got it from because I haven't edited it. This is what it looks like (sorry, I can't give you a link as it's only on my laptop without hunting on the internet again)

Code: Select all

from machine import I2C, Pin
import time

__version__ = '0.2.3'
__author__ = 'Roberto Sánchez'
__license__ = "Apache License 2.0. https://www.apache.org/licenses/LICENSE-2.0"

# I2C address B 0x44 ADDR (pin 2) not connected to VDD
DEFAULT_I2C_ADDRESS = 0x44

# I2C address B 0x45 ADDR (pin 2) connected to VDD
#DEFAULT_I2C_ADDRESS = 0x45


class SHT30:
    """
    SHT30 sensor driver in pure python based on I2C bus

    References:
    * https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/2_Humidity_Sensors/Sensirion_Humidity_Sensors_SHT3x_Datasheet_digital.pdf  # NOQA
    * https://www.wemos.cc/sites/default/files/2016-11/SHT30-DIS_datasheet.pdf
    * https://github.com/wemos/WEMOS_SHT3x_Arduino_Library
    * https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/11_Sample_Codes_Software/Humidity_Sensors/Sensirion_Humidity_Sensors_SHT3x_Sample_Code_V2.pdf
    """
    POLYNOMIAL = 0x131  # P(x) = x^8 + x^5 + x^4 + 1 = 100110001

    ALERT_PENDING_MASK = 0x8000     # 15
    HEATER_MASK = 0x2000            # 13
    RH_ALERT_MASK = 0x0800          # 11
    T_ALERT_MASK = 0x0400           # 10
    RESET_MASK = 0x0010             # 4
    CMD_STATUS_MASK = 0x0002        # 1
    WRITE_STATUS_MASK = 0x0001      # 0

    # MSB = 0x2C LSB = 0x06 Repeatability = High, Clock stretching = enabled
    MEASURE_CMD = b'\x2C\x10'
    STATUS_CMD = b'\xF3\x2D'
    RESET_CMD = b'\x30\xA2'
    CLEAR_STATUS_CMD = b'\x30\x41'
    ENABLE_HEATER_CMD = b'\x30\x6D'
    DISABLE_HEATER_CMD = b'\x30\x66'

    def __init__(self, i2c=None, delta_temp=0, delta_hum=0, i2c_address=DEFAULT_I2C_ADDRESS):
        if i2c is None:
            raise ValueError('An I2C object is required.')
        self.i2c = i2c
        self.i2c_addr = i2c_address
        self.set_delta(delta_temp, delta_hum)
        time.sleep_ms(50)

    def is_present(self):
        """
        Return true if the sensor is correctly conneced, False otherwise
        """
        return self.i2c_addr in self.i2c.scan()

    def set_delta(self, delta_temp=0, delta_hum=0):
        """
        Apply a delta value on the future measurements of temperature and/or humidity
        The units are Celsius for temperature and percent for humidity (can be negative values)
        """
        self.delta_temp = delta_temp
        self.delta_hum = delta_hum

    def _check_crc(self, data):
        # calculates 8-Bit checksum with given polynomial
        crc = 0xFF

        for b in data[:-1]:
            crc ^= b
            for _ in range(8, 0, -1):
                if crc & 0x80:
                    crc = (crc << 1) ^ SHT30.POLYNOMIAL
                else:
                    crc <<= 1
        crc_to_check = data[-1]
        return crc_to_check == crc

    def send_cmd(self, cmd_request, response_size=6, read_delay_ms=100):
        """
        Send a command to the sensor and read (optionally) the response
        The responsed data is validated by CRC
        """
        try:
            self.i2c.writeto(self.i2c_addr, cmd_request)
            if not response_size:
                return
            time.sleep_ms(read_delay_ms)
            data = self.i2c.readfrom(self.i2c_addr, response_size)

            for i in range(response_size//3):
                if not self._check_crc(data[i*3:(i+1)*3]):  # pos 2 and 5 are CRC
                    raise SHT30Error(SHT30Error.CRC_ERROR)
            if data == bytearray(response_size):
                raise SHT30Error(SHT30Error.DATA_ERROR)
            return data
        except OSError as ex:
            raise SHT30Error(SHT30Error.BUS_ERROR)
        except Exception as ex:
            raise ex

    def clear_status(self):
        """
        Clear the status register
        """
        return self.send_cmd(SHT30.CLEAR_STATUS_CMD, None)

    def reset(self):
        """
        Send a soft-reset to the sensor
        """
        return self.send_cmd(SHT30.RESET_CMD, None)

    def status(self, raw=False):
        """
        Get the sensor status register.
        It returns a int value or the bytearray(3) if raw==True
        """
        data = self.send_cmd(SHT30.STATUS_CMD, 3, read_delay_ms=20)

        if raw:
            return data

        status_register = data[0] << 8 | data[1]
        return status_register

    def measure(self, raw=False):
        """
        If raw==True returns a bytearrya(6) with sensor direct measurement otherwise
        It gets the temperature (T) and humidity (RH) measurement and return them.

        The units are Celsius and percent
        """
        data = self.send_cmd(SHT30.MEASURE_CMD, 6)

        if raw:
            return data

        t_celsius = (((data[0] << 8 |  data[1]) * 175) / 0xFFFF) - 45 + self.delta_temp
        rh = (((data[3] << 8 | data[4]) * 100.0) / 0xFFFF) + self.delta_hum
        return t_celsius, rh

    def measure_int(self, raw=False):
        """
        Get the temperature (T) and humidity (RH) measurement using integers.
        If raw==True returns a bytearrya(6) with sensor direct measurement otherwise
        It returns a tuple with 4 values: T integer, T decimal, H integer, H decimal
        For instance to return T=24.0512 and RH= 34.662 This method will return
        (24, 5, 34, 66) Only 2 decimal digits are returned, .05 becomes 5
        Delta values are not applied in this method
        The units are Celsius and percent.
        """
        data = self.send_cmd(SHT30.MEASURE_CMD, 6)
        if raw:
            return data
        aux = (data[0] << 8 | data[1]) * 175
        t_int = (aux // 0xffff) - 45
        t_dec = (aux % 0xffff * 100) // 0xffff
        aux = (data[3] << 8 | data[4]) * 100
        h_int = aux // 0xffff
        h_dec = (aux % 0xffff * 100) // 0xffff
        return t_int, t_dec, h_int, h_dec


class SHT30Error(Exception):
    """
    Custom exception for errors on sensor management
    """
    BUS_ERROR = 0x01
    DATA_ERROR = 0x02
    CRC_ERROR = 0x03

    def __init__(self, error_code=None):
        self.error_code = error_code
        super().__init__(self.get_message())

    def get_message(self):
        if self.error_code == SHT30Error.BUS_ERROR:
            return "Bus error"
        elif self.error_code == SHT30Error.DATA_ERROR:
            return "Data error"
        elif self.error_code == SHT30Error.CRC_ERROR:
            return "CRC error"
        else:
            return "Unknown error"
You can see from this, that someone previously has already edited out the parts you guys were suggesting to me to do.

I'm going to now show you my own code for my SHT30 which I have running on my Pico W.

I've # out the following WDT stuff again:

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#wdt = wdt(timeout= 8000)
#wdt.feed()
#print("woof!...good boy!")
But other than this, this is what I have working right now:

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#Necessary library imports for this code to function
from secrets import SSID
from secrets import PASSWORD
from secrets import IP
from secrets import IP_mask
from secrets import IP_gateway
from secrets import IP_DNS
from secrets import MQTTSERVE
from umqtt.simple import MQTTClient
import time
import network
import ubinascii
import socket
from machine import I2C, Pin, #WDT
import sht30
from sht30 import SHT30
from sht30 import SHT30Error

led = machine.Pin("LED", machine.Pin.OUT)

#initialise LED to OFF
led.off()

def appendfile(message, error):
    file=open("errorlog.txt","a")
    file.write(str(message, error)+",")
    file.close()
    #file.flush()

def sht_error(ex):
    print("something went wrong reading the SHT-30!")
    print('Error:', ex)
    message1 = ', SHT Error: '
    ex2 = str(ex)
    appendfile(message1, ex2) #message, error
    
#Define the interface of the SHT30 Temp/Humidity sensor with the Pico W
i2c=I2C(0, sda=Pin(4), scl=Pin(5), freq=5000)
sht=sht30.SHT30(i2c=i2c, i2c_address=68)

def readsensor():
    global temperature
    global humidity
    try:
        sensor = sht.measure()
    except SHT30Error as ex:
        sht_error(ex)
        try:
            restartsensor = SHT30()
            time.sleep(2)
            restartsensor.reset()
            time.sleep(2)
            sensor = sht.measure()
        except SHT30Error as ex:
            sht_error(ex)
            machine.reset()
    temperature, humidity = sensor

#wdt = WDT(timeout= 8000)
readsensor()
#wdt.feed()
#print("woof!...good boy!")
print('SHT Temperature: {:3.1f}ºC'.format(temperature))
print('SHT Humidity: {:3.1f}%'.format(humidity))

#Define the onboard Pico Temperature sensor and necessary conversion factor
sensor_temp = machine.ADC(4)
conversion_factor = 3.3 / (65535)
 
#Active the onboard Pico W Wi-Fi and connect to home network defined through "secrets.py"
wlan = network.WLAN(network.STA_IF)
wlan.active(True)
print("Scanning Available Wifi Connections...")
#wdt.feed()
#print("woof!...good boy!")
print(wlan.scan())
time.sleep(2)
#wdt.feed()
#print("woof!...good boy!")
print("Connecting to Wifi...")
print()
led.on()
#wdt.feed()
#print("woof!...good boy!")
time.sleep(5)
#wdt.feed()
#print("woof!...good boy!")
try:
    wlan.connect(SSID, PASSWORD)
except:
    try:
        wlan.active(False)
        led.toggle()
        time.sleep(5)
        #wdt.feed()
        #print("woof!...good boy!")
        led.toggle()
        time.sleep(5)
        #wdt.feed()
        #print("woof!...good boy!")
        wlan.active(True)
        time.sleep(5)
        #wdt.feed()
        #print("woof!...good boy!")
        wlan.connect(SSID, PASSWORD)
    except:
        machine.reset()

#wdt.feed()
#print("woof!...good boy!")

#Configure this Pico W for a static IP address on router using the following
UseStaticIP = True
IP = IP
IP_mask = IP_mask
IP_gateway = IP_gateway
IP_DNS = IP_DNS

led.off()

#Read the MAC address from the Pico W itself
mac = ubinascii.hexlify(network.WLAN().config('mac'),':').decode()
print("MAC address for this Pico W:", mac)
# Wait for connect or fail (3mins)
max_wait = 90
while max_wait > 0:
 if wlan.status() < 0 or wlan.status() >= 3:
     #print(wlan.status)
     break
     led.on()
     max_wait -= 1
     print(wlan.status)
     print('waiting for connection...')
     time.sleep(1)
     led.off()
     time.sleep(1)
     #wdt.feed()
     #print("woof!...good boy!")

while max_wait == 0:
     print("cannot connected to the wifi!")
     print("rebooting...")
     led.on()
     time.sleep(5)
     machine.reset()

# Handle connection error
if wlan.status() != 3:
    print("Network connection attempt failed!")
    #raise RuntimeError('network connection attempt failed')
    time.sleep(1)
    machine.reset()
else:
    print("Pico W Wi-Fi is connected to: ",SSID)
    status = wlan.ifconfig()
    print( "ip address for this Pico W: " + status[0] )
    print()
    print("Channel: ", wlan.config('channel'))
    print("SSID: ", wlan.config('essid'))
    print("TXPOWER: ", wlan.config('txpower'))

#wdt.feed()
#print("woof!...good boy!")

#Configure a high power wi-fi connection
wlan.config(pm = 0xa11140)
print()
print("Flashing LEDs for success display")
print()
#wdt.feed()
#print("woof!...good boy!")
#Show some onboard LED flashing to show that attempting to connect to the Wi-Fi has been completed
time.sleep(2)
led.off()
time.sleep(2)
led.toggle()
print("3")
time.sleep(0.2)
led.toggle()
time.sleep(1)
#wdt.feed()
#print("woof!...good boy!")
led.toggle()
print("2")
time.sleep(0.2)
led.toggle()
time.sleep(1)
#wdt.feed()
#print("woof!...good boy!")
led.toggle()
print("1")
time.sleep(0.2)
led.toggle()
time.sleep(1)
led.toggle()
print("blast off!")
print()
#wdt.feed()
#print("woof!...good boy!")
time.sleep(2)

#Setup MQTT server, local client ID (not really required),
#and published data transmissions hierarchy
mqtt_server = MQTTSERVE
client_id = b'PICOW'
#topic_pub1 = b'PicoW/OS_Temp'
#topic_pub2 = b'PicoW/OS_Hum'
#topic_pub3 = b'PicoW/Pico_Temp'
topic_pub1 = b'PicoW/OS_Temp'
topic_pub2 = b'PicoW/OS_Hum'
topic_pub3 = b'PicoW/Pico_Temp'

#For the above topics, use "PicoW/+"
#at the subscriber side to receive all
#three messages at once or use the full
#titles individually i.e PicoW/OS_Temp for
#just the outside temperature variable

def mqtt_connect():
    client = MQTTClient(client_id, mqtt_server, keepalive=3600)
    client.connect()
    print('Connected to %s MQTT Broker'%(mqtt_server))
    return client

def reconnect():
    print('Failed to connect to the MQTT Broker. Rebooting...')
    time.sleep(5)
    machine.reset()

print("Attempting to connect to MQTT Broker...")
print()
#wdt.feed()
#print("woof!...good boy!")

try:
    client = mqtt_connect()
except OSError as mqtterror:
    print(mqtterror)
    message2 = ', MQTT Error: '
    mqtterror2 = str(mqtterror)
    appendfile(message2, mqtterror2)
    reconnect()

#wdt.feed()
#print("woof!...good boy!")
    
#The main script of repeativeness for reading in from the connected sensor
#and taking in onboard temperature readings
while True:                                  #do stuff here
    led.on()
    time.sleep(0.5)

#Collect readings from the SHT-30
    readsensor()
    
    #wdt.feed()
    #print("woof!...good boy!")

#Collect temperature reading for the Pico W CPU
    def cpumeasure():
        global picotemp
        try:
            reading = sensor_temp.read_u16() * conversion_factor 
            picotemp = 27 - (reading - 0.706)/0.001721
        except OSError as cpu:
            print("something went wrong reading the onboard CPU Temperature!")
            print(cpu)
            print("rebooting...")
            message3 = ', CPU Temp Error: '
            cpu2 = str(cpu)
            appendfile(message3, cpu2)
            time.sleep(5)
            machine.reset()

    cpumeasure()
    #make readings 1 decimal place
    tpm1 = round(temperature,1)
    tpm2 = round(humidity,1)
    tpm3 = round(picotemp,1)
    
    #convert float reading values into bytes ready for MQTT transmission
    tpm4 = f"{tpm1}".encode()
    tpm5 = f"{tpm2}".encode()
    tpm6 = f"{tpm3}".encode()
    
    topic_msg1 = tpm4
    topic_msg2 = tpm5
    topic_msg3 = tpm6
    
    #Message displayed to the screen
    print()
    print("Publishing...")
    print()
    print('SHT Temperature: {:3.1f}ºC'.format(tpm1))
    print('SHT Humidity: {:3.1f}%'.format(tpm2))
    print('Pico W Temperature: {:3.1f}ºC'.format(tpm3))
    print()
    
    #Equivalent transmission of displayed readings above
    #(reverse order to match above order on subscriber receipt)
    try:
        client.publish(topic_pub3, topic_msg3)
        client.publish(topic_pub2, topic_msg2)
        client.publish(topic_pub1, topic_msg1)
        print("Publishing complete")
    except:
        print("Disconnected from MQTT Broker! Attempting Reconnection...")
        print()
        try:
            client = mqtt_connect()
        except OSError as mqtterror:
            print(mqtterror)
            message4 = ', MQTT2 Error: '
            mqtterror3 = str(mqtterror)
            appendfile(message4, mqtterror3)
            reconnect()
    led.off()
    #wdt.feed()
    #print("woof!...good boy!")
    time.sleep(5)
    #wdt.feed()
    #print("woof!...good boy!")
    time.sleep(5)
If I change the I2C address from 68 (correct) to 67 (wrong) in order to force an error, this is the results from this code:

Thonny Screen Error:

Code: Select all

something went wrong reading the SHT-30!
Error: Bus error
Traceback (most recent call last):
  File "<stdin>", line 60, in <module>
  File "<stdin>", line 49, in readsensor
  File "sht30.py", line 45, in __init__
ValueError: An I2C object is required.
and the errorlog.txt gets this error message logged into it:

Code: Select all

, SHT Error: ,
I have two things I'm asking for help with.

1. Why doesn't my restart sensor code work?

Code: Select all

from sht30 import SHT30
restartsensor = SHT30()
restartsensor.reset()
2. Why doesn't my SHTError code "ex" get printed to my errorlog.txt file along with the ", SHT Error: ,"?

Is anyone clever enough to show me what I need to do to fix these please?

jahr
Posts: 11
Joined: Fri Apr 02, 2021 1:20 pm

Re: Pico W Micro Python for SHT30 Temp/Humidity HELP!

Post by jahr » Wed Nov 09, 2022 8:44 am

Rissy wrote:
Tue Nov 08, 2022 7:05 pm
1. Why doesn't my restart sensor code work?

Code: Select all

from sht30 import SHT30
restartsensor = SHT30()
restartsensor.reset()
Hello Rissy, even when reseting the sensor you need to initialize it with i2c:

Code: Select all

from machine import I2C, Pin
from sht30 import SHT30
i2c=I2C(0, sda=Pin(4), scl=Pin(5))
restartsensor = SHT30(i2c)
restartsensor.reset()
As far as I know, the sensor is reset automatically on poweron, so it is not necessary to do it manually this way.

Rissy
Posts: 116
Joined: Sun Aug 14, 2022 8:15 am

Re: Pico W Micro Python for SHT30 Temp/Humidity HELP!

Post by Rissy » Wed Nov 09, 2022 9:00 am

jahr wrote:
Wed Nov 09, 2022 8:44 am
Rissy wrote:
Tue Nov 08, 2022 7:05 pm
1. Why doesn't my restart sensor code work?

Code: Select all

from sht30 import SHT30
restartsensor = SHT30()
restartsensor.reset()
Hello Rissy, even when reseting the sensor you need to initialize it with i2c:

Code: Select all

from machine import I2C, Pin
from sht30 import SHT30
i2c=I2C(0, sda=Pin(4), scl=Pin(5))
restartsensor = SHT30(i2c)
restartsensor.reset()
As far as I know, the sensor is reset automatically on poweron, so it is not necessary to do it manually this way.
Ah! I see! It didn't express that in the guys instructions!

I need to try as much as possible to combat my I2C link to my sensor going bad randomly every time it rains outside. There is something which upsets it when it rains, and presumably the (weather proof) sensor or the connecting cable gets wet. I don't know what the actual issue is or how to fix it. So right now, i'm using the watchdog to recover from a crashed sensor condition, but I wanted to try the sensor reset in place of the watchdog.

...Unless you can suggest another route?

User avatar
Roberthh
Posts: 3667
Joined: Sat May 09, 2015 4:13 pm
Location: Rhineland, Europe

Re: Pico W Micro Python for SHT30 Temp/Humidity HELP!

Post by Roberthh » Wed Nov 09, 2022 9:40 am

How long is the wire between the board and the sensor? I2C is designed for short wires, like < 30 cm. Using lower frequencies helps, as well as making the pull-up resistors as small as possible. For rp2 Pico, 330 Ohm should be fine, resulting in ~10mA sunk.
And what kind of error message do you get.

Rissy
Posts: 116
Joined: Sun Aug 14, 2022 8:15 am

Re: Pico W Micro Python for SHT30 Temp/Humidity HELP!

Post by Rissy » Wed Nov 09, 2022 1:04 pm

Roberthh wrote:
Wed Nov 09, 2022 9:40 am
How long is the wire between the board and the sensor? I2C is designed for short wires, like < 30 cm. Using lower frequencies helps, as well as making the pull-up resistors as small as possible. For rp2 Pico, 330 Ohm should be fine, resulting in ~10mA sunk.
And what kind of error message do you get.
I'm aware of the intentions of I2C being designed for short rather than long cable runs. That being said, I've reduced the Frequency down to 5,000Hz (checked again last night) although I've proven it works as fast as 50,000Hz too. My cable run is about 6m in total from Pico W to SHT30 Sensor (1m premade cable from manufacture of the sensor assembly from the Pi Hut in the UK, and an additional 5m of installed cabling by me. The cable ends are connected together in a weather proof junction box outside, and my installed cable is high quality Belden Shielded RS485 cabling. The premade cabled assembly from the Pi Hut is sealed from manufacture, and already has within this, the resistors, but I couldn't tell you what value of resistance they've installed unfortunately because I cannot get at them (All glued together). So resistance is not something I can adjust lower, only higher (I guess) if I put more resistance across whichever wires it is that I would need to try.

As for what message I get. This is the ultimate question, and why I want to log the error message (ex from my code) into my errorlog.txt file as it happens only when it rains heavily outside, and without my laptop connected to the Pico W at exactly the time it has the error, then I am unable to see what the error is! This is why I am asking for help to understand why my error message is not being logged from my previous posts.

User avatar
Roberthh
Posts: 3667
Joined: Sat May 09, 2015 4:13 pm
Location: Rhineland, Europe

Re: Pico W Micro Python for SHT30 Temp/Humidity HELP!

Post by Roberthh » Wed Nov 09, 2022 1:33 pm

You can measure the existing pull-up resistors between a data line and Vcc, if the sensor is not powered. And you can always connect additional resistors fomr SDA to Vcc and SCL to Vcc. They would be simply in parallel to the existing resistor. Let's assume, the existing value is 4700, and you add 390 Ohm. Then the resulting value is 1 / ((1 / 4700) + (1 / 390)) = 360.

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