How many grams of coffee did I add to my pour-over?

Is the bag of cat food empty?

Did I remember to water the plant? 

What's the weight of these screws in my workshop?

To answer these questions (and more), you're going to build an internet-enabled scale to track weight data over a period of time.

To do this, you'll be performing a bit of hardware hacking - tearing down a DYMO Postage scale and soldering wires to connect it to a PyPortal. Then, you'll add some CircuitPython code to the PyPortal which allows you to read the the scale remotely using Adafruit IO - our easy-to-use internet of things service.

This scale is not just for keeping track of your coffee - you can can monitor anything! Here are some examples:

  • Place a bag of cat food on the scale and enable Adafruit IO Feed Email Notifications for when you run out of cat food.
  • Science experiments - no need to watch and chart a scale's weight - let Adafruit IO do that for you with automatic graph visualizations!
  • Are you a beekeeper? Track the weight of a honeycomb and have Adafruit IO notify you when it exceeds a certain weight.

This is an introduction to hacking and controlling consumer off-the-shelf electronics with CircuitPython. To perform this guide, you'll need some soldering experience and willingness to tear down a consumer product your purchased.

Adafruit IO

 

Adafruit IO is the easiest way to stream, log, and interact with your data. It's built from the ground up to be easy to use - we do the hard stuff so you can focus on the fun stuff.

Data such as temperature and light levels can be hard to visualize and quantify - Adafruit IO makes it simple. Send IO your data and it can store and display it using charts, graphs, gauges, and more!

CircuitPython Code

 

CircuitPython is great for building Internet-of-Things projects. Using the Adafruit IO CircuitPython module, you can easily send data to Adafruit IO, receive data from Adafruit IO, and easily manipulate data with the powerful Adafruit IO API.

We've also built a DymoScale module for CircuitPython to make interfacing with these scales incredibly easy. 

You can rapidly update your code without having to compile and store WiFi and API secret keys on the device. This means that there's no editing code and re-uploading whenever you move the PyPortal to another network - just update a file and you're set. 

Parts

WARNING: Follow the steps in this guide at your own risk! DYMO Scales are not designed to be taken apart and soldered to. Following this guide WILL void your warranty.

To use this guide, you'll need a DYMO scale. We've tested this guide with DYMO M25 and a DYMO M10.

Note: There are differences between the two scale models we tested (the CircuitPython_DymoScale library handles this for you, you can use either). If you choose to use another DYMO mode with this guide, be warned that we have not tested other DYMO scales with this library and your scale may not work with our library. 

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Materials

You'll need the following materials to complete this guide. If you do not have them handy, consider picking them up from Adafruit:

1 x Soldering Station
Digital Genuine Hakko FX-888D
1 x Solder Spool
Solder Wire - 60/40 Rosin Core
1 x Wire Strippers
Hakko Professional Quality 20-30 AWG Wire Strippers - CSP-30-1
1 x Spudger
Spudger - Double Sided Prying Tool
1 x Screwdriver
Adafruit Pocket Screwdriver
1 x USB Cable
USB cable - USB A to Micro-B - 3 foot long

CircuitPython is a derivative of MicroPython designed to simplify experimentation and education on low-cost microcontrollers. It makes it easier than ever to get prototyping by requiring no upfront desktop software downloads. Simply copy and edit files on the CIRCUITPY "flash" drive to iterate.

The following instructions will show you how to install CircuitPython. If you've already installed CircuitPython but are looking to update it or reinstall it, the same steps work for that as well!

Set up CircuitPython Quick Start!

Follow this quick step-by-step for super-fast Python power :)

Click the link above to download the latest version of CircuitPython for the PyPortal.

Download and save it to your desktop (or wherever is handy).

Plug your PyPortal into your computer using a known-good USB cable.

A lot of people end up using charge-only USB cables and it is very frustrating! So make sure you have a USB cable you know is good for data sync.

Double-click the Reset button on the top in the middle (magenta arrow) on your board, and you will see the NeoPixel RGB LED (green arrow) turn green. If it turns red, check the USB cable, try another USB port, etc. Note: The little red LED next to the USB connector will pulse red. That's ok!

If double-clicking doesn't work the first time, try again. Sometimes it can take a few tries to get the rhythm right!

You will see a new disk drive appear called PORTALBOOT.

Drag the adafruit-circuitpython-pyportal-<whatever>.uf2 file to PORTALBOOT.

The LED will flash. Then, the PORTALBOOT drive will disappear and a new disk drive called CIRCUITPY will appear.

If you haven't added any code to your board, the only file that will be present is boot_out.txt. This is absolutely normal! It's time for you to add your code.py and get started!

That's it, you're done! :)

PyPortal Default Files

Click below to download a zip of the files that shipped on the PyPortal or PyPortal Pynt.

WARNING: Disassemble the Dymo Scale at your own risk! Remember the Dymo Scale is not designed to be opened by users and will require some force to open. Take the proper safety precautions to protect your eyes and body from harm when using tools to open the scale. The instructions below are a suggestion and they might not work with current or future Dymo Scales.

Take your scale out of the box - it's hardware hackin' time!

We're going to begin by popping the front faceplate off.

Run a spudger along the top edge of the scale's faceplate, from right to left. You should feel the faceplate pop as you run it along.

Once the spudger reaches the end of the faceplate, it should pop off.

Then, remove the front faceplate from the scale.

Flip the scale over - at the end of the scale are removable rubber feet, pop these out with a flathead screwdriver or a spudger.

We used the Adafruit Pocket Screwdriver - the precision screwdriver set we usually use don't have a long enough shaft to reach the screw.

Unscrew both screws from the bottom of the scale. 

After the screws are removed, the top cover should remove cleanly without any extra force.

Using a spudger, gently pry at the seam between the scale's top cover and the base.

As you go along the edges of the scale, the plastic will pop. Do not force the spudger in any direction other than sideways - you'll risk breaking the scale's thin plastic cover.

Continue running the spudger along the scale's seams until you've gone completely around the scale. When you get to the front of the scale (near the LCD), you'll be running the spudger towards the bottom of the scale's base. 

Do not completely remove the cover - there are wires still connected to the front panel!

Slowly remove the cover, tilting it slowly towards the front of the scale.

Do not completely remove the cover - there are wires connected to the front panel

With the cover slightly open, you may notice some wires snagging. With your spudger or a dull screwdriver, move these wires away from the plastic posts so they do not snap when you open the case fully.

Remove the foam adhesive on the right and left sides of the scale. This will let the PCB move around more, giving you more wiggle-room to solder later.

Flip over the PCB and preheat your soldering iron for the next few steps.

Wiring

We're going to be soldering to the trace highlighted.

Locate this trace on the PCB - it should be directly above the T28 silkscreen text.

We can not solder to the board until we've removed the solder mask.

Using a flathead screwdriver, scrape off the green solder-mask until you've revealed the copper underneath.

Be careful to scrape up-and-down, instead of left-to-right, so you don't accidentally cut the trace.

With a pair of wire cutters, remove the header plug from the end of the white wire.

Then, using a pair of wire strippers, strip a short (~2mm) length of wire from the end of the white wire. 

Tin the copper pad you exposed with the razor by applying a small amount of solder to it. Then, tack the wire to the pad by heating the wire with the soldering iron.

The connection between the white wire and this pad is still fragile. Using kapton tape, or a dab of hot glue, secure the white wire to the back of the board.

Solder the red header pin to the USB V+ pin on the left side of the board.

Then, solder the black header pin to the USB VSS pin

Check out the right side of the board. There's two red wires below a white box on the PCB attached to the KG/LB button.

Note: On the DYMO M-25 model, this button is labeled G/OZ instead of KG/LB.

Using wire cutters, remove the header pins from a 3-Pin JST-PH cable.

Then, with a pair of wire strippers, strip off a small amount of the rubber sheathing covering each pin.

Solder the white wire from the JST cable to the KG/LB (or G/OZ) pad on the PCB.

Solder the black wire from the JST cable to the GND pad on the PCB.

Re-Assembly and PyPortal Wiring

Before you re-assemble the PyPortal, make sure the connections for the kg/oz button and data pins are still connected.

The rectangular holes in the scale's faceplate are perfect for wires to be threaded through them.

Thread the cables through the rectangular holes in the faceplate.

Then, place the top of the scale onto the metal top plate and re-attach the screws underneath the scale to secure the top of the scale.

On the right side of the PyPortal are two 3-Pin JST-PH connectors. These connectors can be used for analog or digital communication.

Connect the 3-Pin JST-PH connector from the button to D3 on the PyPortal.

Connect the other 3-Pin JST-PH connector for the scale data to D4 on the PyPortal.

We're done! Lets move onto the software to control and communicate with the DYMO scale.

Once you have CircuitPython setup and libraries installed we can get your board connected to the Internet. Note that access to enterprise level secured WiFi networks is not currently supported, only WiFi networks that require SSID and password.

To get connected, you will need to start by creating a secrets file.

What's a secrets file?

We expect people to share tons of projects as they build CircuitPython WiFi widgets. What we want to avoid is people accidentally sharing their passwords or secret tokens and API keys. So, we designed all our examples to use a secrets.py file, that is in your CIRCUITPY drive, to hold secret/private/custom data. That way you can share your main project without worrying about accidentally sharing private stuff.

Your secrets.py file should look like this:

# This file is where you keep secret settings, passwords, and tokens!
# If you put them in the code you risk committing that info or sharing it

secrets = {
    'ssid' : 'home ssid',
    'password' : 'my password',
    'timezone' : "America/New_York", # http://worldtimeapi.org/timezones
    'github_token' : 'fawfj23rakjnfawiefa',
    'hackaday_token' : 'h4xx0rs3kret',
    }

Inside is a python dictionary named secrets with a line for each entry. Each entry has an entry name (say 'ssid') and then a colon to separate it from the entry key 'home ssid' and finally a comma ,

At a minimum you'll need the ssid and password for your local WiFi setup. As you make projects you may need more tokens and keys, just add them one line at a time. See for example other tokens such as one for accessing github or the hackaday API. Other non-secret data like your timezone can also go here, just cause it's called secrets doesn't mean you can't have general customization data in there!

For the correct time zone string, look at http://worldtimeapi.org/timezones and remember that if your city is not listed, look for a city in the same time zone, for example Boston, New York, Philadelphia, Washington DC, and Miami are all on the same time as New York.

Of course, don't share your secrets.py - keep that out of GitHub, Discord or other project-sharing sites.

Connect to WiFi

OK now you have your secrets setup - you can connect to the Internet. Lets use the ESP32SPI and the Requests libraries - you'll need to visit the CircuitPython bundle and install:

  • adafruit_bus_device
  • adafruit_esp32spi
  • adafruit_requests
  • neopixel

Into your lib folder. Once that's done, load up the following example using Mu or your favorite editor:

# SPDX-FileCopyrightText: 2019 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT

import board
import busio
from digitalio import DigitalInOut
import adafruit_requests as requests
import adafruit_esp32spi.adafruit_esp32spi_socket as socket
from adafruit_esp32spi import adafruit_esp32spi

# Get wifi details and more from a secrets.py file
try:
    from secrets import secrets
except ImportError:
    print("WiFi secrets are kept in secrets.py, please add them there!")
    raise

print("ESP32 SPI webclient test")

TEXT_URL = "http://wifitest.adafruit.com/testwifi/index.html"
JSON_URL = "http://api.coindesk.com/v1/bpi/currentprice/USD.json"


# If you are using a board with pre-defined ESP32 Pins:
esp32_cs = DigitalInOut(board.ESP_CS)
esp32_ready = DigitalInOut(board.ESP_BUSY)
esp32_reset = DigitalInOut(board.ESP_RESET)

# If you have an AirLift Shield:
# esp32_cs = DigitalInOut(board.D10)
# esp32_ready = DigitalInOut(board.D7)
# esp32_reset = DigitalInOut(board.D5)

# If you have an AirLift Featherwing or ItsyBitsy Airlift:
# esp32_cs = DigitalInOut(board.D13)
# esp32_ready = DigitalInOut(board.D11)
# esp32_reset = DigitalInOut(board.D12)

# If you have an externally connected ESP32:
# NOTE: You may need to change the pins to reflect your wiring
# esp32_cs = DigitalInOut(board.D9)
# esp32_ready = DigitalInOut(board.D10)
# esp32_reset = DigitalInOut(board.D5)

spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
esp = adafruit_esp32spi.ESP_SPIcontrol(spi, esp32_cs, esp32_ready, esp32_reset)

requests.set_socket(socket, esp)

if esp.status == adafruit_esp32spi.WL_IDLE_STATUS:
    print("ESP32 found and in idle mode")
print("Firmware vers.", esp.firmware_version)
print("MAC addr:", [hex(i) for i in esp.MAC_address])

for ap in esp.scan_networks():
    print("\t%s\t\tRSSI: %d" % (str(ap["ssid"], "utf-8"), ap["rssi"]))

print("Connecting to AP...")
while not esp.is_connected:
    try:
        esp.connect_AP(secrets["ssid"], secrets["password"])
    except RuntimeError as e:
        print("could not connect to AP, retrying: ", e)
        continue
print("Connected to", str(esp.ssid, "utf-8"), "\tRSSI:", esp.rssi)
print("My IP address is", esp.pretty_ip(esp.ip_address))
print(
    "IP lookup adafruit.com: %s" % esp.pretty_ip(esp.get_host_by_name("adafruit.com"))
)
print("Ping google.com: %d ms" % esp.ping("google.com"))

# esp._debug = True
print("Fetching text from", TEXT_URL)
r = requests.get(TEXT_URL)
print("-" * 40)
print(r.text)
print("-" * 40)
r.close()

print()
print("Fetching json from", JSON_URL)
r = requests.get(JSON_URL)
print("-" * 40)
print(r.json())
print("-" * 40)
r.close()

print("Done!")

And save it to your board, with the name code.py

Don't forget you'll also need to create the secrets.py file as seen above, with your WiFi ssid and password.

In a serial console, you should see something like the following. For more information about connecting with a serial console, view the guide Connecting to the Serial Console.

In order, the example code...

Initializes the ESP32 over SPI using the SPI port and 3 control pins:

esp32_cs = DigitalInOut(board.ESP_CS)
esp32_ready = DigitalInOut(board.ESP_BUSY)
esp32_reset = DigitalInOut(board.ESP_RESET)

spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
esp = adafruit_esp32spi.ESP_SPIcontrol(spi, esp32_cs, esp32_ready, esp32_reset)

Tells our requests library the type of socket we're using (socket type varies by connectivity type - we'll be using the adafruit_esp32spi_socket for this example). We'll also set the interface to an esp object. This is a little bit of a hack, but it lets us use requests like CPython does.

requests.set_socket(socket, esp)

Verifies an ESP32 is found, checks the firmware and MAC address

if esp.status == adafruit_esp32spi.WL_IDLE_STATUS:
    print("ESP32 found and in idle mode")
print("Firmware vers.", esp.firmware_version)
print("MAC addr:", [hex(i) for i in esp.MAC_address])

Performs a scan of all access points it can see and prints out the name and signal strength:

for ap in esp.scan_networks():
    print("\t%s\t\tRSSI: %d" % (str(ap['ssid'], 'utf-8'), ap['rssi']))

Connects to the AP we've defined here, then prints out the local IP address, attempts to do a domain name lookup and ping google.com to check network connectivity (note sometimes the ping fails or takes a while, this isn't a big deal)

print("Connecting to AP...")
while not esp.is_connected:
    try:
        esp.connect_AP(secrets["ssid"], secrets["password"])
    except RuntimeError as e:
        print("could not connect to AP, retrying: ", e)
        continue
print("Connected to", str(esp.ssid, "utf-8"), "\tRSSI:", esp.rssi)
print("My IP address is", esp.pretty_ip(esp.ip_address))
print(
    "IP lookup adafruit.com: %s" % esp.pretty_ip(esp.get_host_by_name("adafruit.com"))

OK now we're getting to the really interesting part. With a SAMD51 or other large-RAM (well, over 32 KB) device, we can do a lot of neat tricks. Like for example we can implement an interface a lot like requests - which makes getting data really really easy

To read in all the text from a web URL call requests.get - you can pass in https URLs for SSL connectivity

TEXT_URL = "http://wifitest.adafruit.com/testwifi/index.html"
print("Fetching text from", TEXT_URL)
r = requests.get(TEXT_URL)
print('-'*40)
print(r.text)
print('-'*40)
r.close()

Or, if the data is in structured JSON, you can get the json pre-parsed into a Python dictionary that can be easily queried or traversed. (Again, only for nRF52840, M4 and other high-RAM boards)

JSON_URL = "http://api.coindesk.com/v1/bpi/currentprice/USD.json"
print("Fetching json from", JSON_URL)
r = requests.get(JSON_URL)
print('-'*40)
print(r.json())
print('-'*40)
r.close()

Requests

We've written a requests-like library for web interfacing named Adafruit_CircuitPython_Requests. This library allows you to send HTTP/1.1 requests without "crafting" them and provides helpful methods for parsing the response from the server.

# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT

# adafruit_requests usage with an esp32spi_socket
import board
import busio
from digitalio import DigitalInOut
import adafruit_esp32spi.adafruit_esp32spi_socket as socket
from adafruit_esp32spi import adafruit_esp32spi
import adafruit_requests as requests

# Add a secrets.py to your filesystem that has a dictionary called secrets with "ssid" and
# "password" keys with your WiFi credentials. DO NOT share that file or commit it into Git or other
# source control.
# pylint: disable=no-name-in-module,wrong-import-order
try:
    from secrets import secrets
except ImportError:
    print("WiFi secrets are kept in secrets.py, please add them there!")
    raise

# If you are using a board with pre-defined ESP32 Pins:
esp32_cs = DigitalInOut(board.ESP_CS)
esp32_ready = DigitalInOut(board.ESP_BUSY)
esp32_reset = DigitalInOut(board.ESP_RESET)

# If you have an externally connected ESP32:
# esp32_cs = DigitalInOut(board.D9)
# esp32_ready = DigitalInOut(board.D10)
# esp32_reset = DigitalInOut(board.D5)

# If you have an AirLift Featherwing or ItsyBitsy Airlift:
# esp32_cs = DigitalInOut(board.D13)
# esp32_ready = DigitalInOut(board.D11)
# esp32_reset = DigitalInOut(board.D12)

spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
esp = adafruit_esp32spi.ESP_SPIcontrol(spi, esp32_cs, esp32_ready, esp32_reset)

print("Connecting to AP...")
while not esp.is_connected:
    try:
        esp.connect_AP(secrets["ssid"], secrets["password"])
    except RuntimeError as e:
        print("could not connect to AP, retrying: ", e)
        continue
print("Connected to", str(esp.ssid, "utf-8"), "\tRSSI:", esp.rssi)

# Initialize a requests object with a socket and esp32spi interface
socket.set_interface(esp)
requests.set_socket(socket, esp)

TEXT_URL = "http://wifitest.adafruit.com/testwifi/index.html"
JSON_GET_URL = "https://httpbin.org/get"
JSON_POST_URL = "https://httpbin.org/post"

print("Fetching text from %s" % TEXT_URL)
response = requests.get(TEXT_URL)
print("-" * 40)

print("Text Response: ", response.text)
print("-" * 40)
response.close()

print("Fetching JSON data from %s" % JSON_GET_URL)
response = requests.get(JSON_GET_URL)
print("-" * 40)

print("JSON Response: ", response.json())
print("-" * 40)
response.close()

data = "31F"
print("POSTing data to {0}: {1}".format(JSON_POST_URL, data))
response = requests.post(JSON_POST_URL, data=data)
print("-" * 40)

json_resp = response.json()
# Parse out the 'data' key from json_resp dict.
print("Data received from server:", json_resp["data"])
print("-" * 40)
response.close()

json_data = {"Date": "July 25, 2019"}
print("POSTing data to {0}: {1}".format(JSON_POST_URL, json_data))
response = requests.post(JSON_POST_URL, json=json_data)
print("-" * 40)

json_resp = response.json()
# Parse out the 'json' key from json_resp dict.
print("JSON Data received from server:", json_resp["json"])
print("-" * 40)
response.close()

The code first sets up the ESP32SPI interface. Then, it initializes a request object using an ESP32 socket and the esp object.

import board
import busio
from digitalio import DigitalInOut
import adafruit_esp32spi.adafruit_esp32spi_socket as socket
from adafruit_esp32spi import adafruit_esp32spi
import adafruit_requests as requests

# If you are using a board with pre-defined ESP32 Pins:
esp32_cs = DigitalInOut(board.ESP_CS)
esp32_ready = DigitalInOut(board.ESP_BUSY)
esp32_reset = DigitalInOut(board.ESP_RESET)

# If you have an externally connected ESP32:
# esp32_cs = DigitalInOut(board.D9)
# esp32_ready = DigitalInOut(board.D10)
# esp32_reset = DigitalInOut(board.D5)

spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
esp = adafruit_esp32spi.ESP_SPIcontrol(spi, esp32_cs, esp32_ready, esp32_reset)

print("Connecting to AP...")
while not esp.is_connected:
    try:
        esp.connect_AP(b'MY_SSID_NAME', b'MY_SSID_PASSWORD')
    except RuntimeError as e:
        print("could not connect to AP, retrying: ",e)
        continue
print("Connected to", str(esp.ssid, 'utf-8'), "\tRSSI:", esp.rssi)

# Initialize a requests object with a socket and esp32spi interface
requests.set_socket(socket, esp)

HTTP GET with Requests

The code makes a HTTP GET request to Adafruit's WiFi testing website - http://wifitest.adafruit.com/testwifi/index.html.

To do this, we'll pass the URL into requests.get(). We're also going to save the response from the server into a variable named response.

While we requested data from the server, we'd what the server responded with. Since we already saved the server's response, we can read it back. Luckily for us, requests automatically decodes the server's response into human-readable text, you can read it back by calling response.text.

Lastly, we'll perform a bit of cleanup by calling response.close(). This closes, deletes, and collect's the response's data. 

print("Fetching text from %s"%TEXT_URL)
response = requests.get(TEXT_URL)
print('-'*40)

print("Text Response: ", response.text)
print('-'*40)
response.close()

While some servers respond with text, some respond with json-formatted data consisting of attribute–value pairs.

CircuitPython_Requests can convert a JSON-formatted response from a server into a CPython dict. object.

We can also fetch and parse json data. We'll send a HTTP get to a url we know returns a json-formatted response (instead of text data). 

Then, the code calls response.json() to convert the response to a CPython dict

print("Fetching JSON data from %s"%JSON_GET_URL)
response = requests.get(JSON_GET_URL)
print('-'*40)

print("JSON Response: ", response.json())
print('-'*40)
response.close()

HTTP POST with Requests

Requests can also POST data to a server by calling the requests.post method, passing it a data value.

data = '31F'
print("POSTing data to {0}: {1}".format(JSON_POST_URL, data))
response = requests.post(JSON_POST_URL, data=data)
print('-'*40)

json_resp = response.json()
# Parse out the 'data' key from json_resp dict.
print("Data received from server:", json_resp['data'])
print('-'*40)
response.close()

You can also post json-formatted data to a server by passing json_data into the requests.post method.

    json_data = {"Date" : "July 25, 2019"}
print("POSTing data to {0}: {1}".format(JSON_POST_URL, json_data))
response = requests.post(JSON_POST_URL, json=json_data)
print('-'*40)

json_resp = response.json()
# Parse out the 'json' key from json_resp dict.
print("JSON Data received from server:", json_resp['json'])
print('-'*40)
response.close()
  

Advanced Requests Usage

Want to send custom HTTP headers, parse the response as raw bytes, or handle a response's http status code in your CircuitPython code?

We've written an example to show advanced usage of the requests module below.

# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT

import board
import busio
from digitalio import DigitalInOut
import adafruit_esp32spi.adafruit_esp32spi_socket as socket
from adafruit_esp32spi import adafruit_esp32spi
import adafruit_requests as requests

# Add a secrets.py to your filesystem that has a dictionary called secrets with "ssid" and
# "password" keys with your WiFi credentials. DO NOT share that file or commit it into Git or other
# source control.
# pylint: disable=no-name-in-module,wrong-import-order
try:
    from secrets import secrets
except ImportError:
    print("WiFi secrets are kept in secrets.py, please add them there!")
    raise

# If you are using a board with pre-defined ESP32 Pins:
esp32_cs = DigitalInOut(board.ESP_CS)
esp32_ready = DigitalInOut(board.ESP_BUSY)
esp32_reset = DigitalInOut(board.ESP_RESET)

# If you have an externally connected ESP32:
# esp32_cs = DigitalInOut(board.D9)
# esp32_ready = DigitalInOut(board.D10)
# esp32_reset = DigitalInOut(board.D5)

spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
esp = adafruit_esp32spi.ESP_SPIcontrol(spi, esp32_cs, esp32_ready, esp32_reset)

print("Connecting to AP...")
while not esp.is_connected:
    try:
        esp.connect_AP(secrets["ssid"], secrets["password"])
    except RuntimeError as e:
        print("could not connect to AP, retrying: ", e)
        continue
print("Connected to", str(esp.ssid, "utf-8"), "\tRSSI:", esp.rssi)

# Initialize a requests object with a socket and esp32spi interface
socket.set_interface(esp)
requests.set_socket(socket, esp)

JSON_GET_URL = "http://httpbin.org/get"

# Define a custom header as a dict.
headers = {"user-agent": "blinka/1.0.0"}

print("Fetching JSON data from %s..." % JSON_GET_URL)
response = requests.get(JSON_GET_URL, headers=headers)
print("-" * 60)

json_data = response.json()
headers = json_data["headers"]
print("Response's Custom User-Agent Header: {0}".format(headers["User-Agent"]))
print("-" * 60)

# Read Response's HTTP status code
print("Response HTTP Status Code: ", response.status_code)
print("-" * 60)

# Close, delete and collect the response data
response.close()

WiFi Manager

That simpletest example works but it's a little finicky - you need to constantly check WiFi status and have many loops to manage connections and disconnections. For more advanced uses, we recommend using the WiFiManager object. It will wrap the connection/status/requests loop for you - reconnecting if WiFi drops, resetting the ESP32 if it gets into a bad state, etc.

Here's a more advanced example that shows the WiFi manager and also how to POST data with some extra headers:

# SPDX-FileCopyrightText: 2019 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT

import time
import board
import busio
from digitalio import DigitalInOut
import neopixel
from adafruit_esp32spi import adafruit_esp32spi
from adafruit_esp32spi import adafruit_esp32spi_wifimanager

print("ESP32 SPI webclient test")

# Get wifi details and more from a secrets.py file
try:
    from secrets import secrets
except ImportError:
    print("WiFi secrets are kept in secrets.py, please add them there!")
    raise

# If you are using a board with pre-defined ESP32 Pins:
esp32_cs = DigitalInOut(board.ESP_CS)
esp32_ready = DigitalInOut(board.ESP_BUSY)
esp32_reset = DigitalInOut(board.ESP_RESET)

# If you have an externally connected ESP32:
# esp32_cs = DigitalInOut(board.D9)
# esp32_ready = DigitalInOut(board.D10)
# esp32_reset = DigitalInOut(board.D5)

spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
esp = adafruit_esp32spi.ESP_SPIcontrol(spi, esp32_cs, esp32_ready, esp32_reset)
"""Use below for Most Boards"""
status_light = neopixel.NeoPixel(
    board.NEOPIXEL, 1, brightness=0.2
)  # Uncomment for Most Boards
"""Uncomment below for ItsyBitsy M4"""
# status_light = dotstar.DotStar(board.APA102_SCK, board.APA102_MOSI, 1, brightness=0.2)
# Uncomment below for an externally defined RGB LED
# import adafruit_rgbled
# from adafruit_esp32spi import PWMOut
# RED_LED = PWMOut.PWMOut(esp, 26)
# GREEN_LED = PWMOut.PWMOut(esp, 27)
# BLUE_LED = PWMOut.PWMOut(esp, 25)
# status_light = adafruit_rgbled.RGBLED(RED_LED, BLUE_LED, GREEN_LED)
wifi = adafruit_esp32spi_wifimanager.ESPSPI_WiFiManager(esp, secrets, status_light)

counter = 0

while True:
    try:
        print("Posting data...", end="")
        data = counter
        feed = "test"
        payload = {"value": data}
        response = wifi.post(
            "https://io.adafruit.com/api/v2/"
            + secrets["aio_username"]
            + "/feeds/"
            + feed
            + "/data",
            json=payload,
            headers={"X-AIO-KEY": secrets["aio_key"]},
        )
        print(response.json())
        response.close()
        counter = counter + 1
        print("OK")
    except (ValueError, RuntimeError) as e:
        print("Failed to get data, retrying\n", e)
        wifi.reset()
        continue
    response = None
    time.sleep(15)

You'll note here we use a secrets.py file to manage our SSID info. The wifimanager is given the ESP32 object, secrets and a neopixel for status indication.

Note, you'll need to add a some additional information to your secrets file so that the code can query the Adafruit IO API:

  • aio_username
  • aio_key

You can go to your adafruit.io View AIO Key link to get those two values and add them to the secrets file, which will now look something like this:

# This file is where you keep secret settings, passwords, and tokens!
# If you put them in the code you risk committing that info or sharing it

secrets = {
    'ssid' : '_your_ssid_',
    'password' : '_your_wifi_password_',
    'timezone' : "America/Los_Angeles", # http://worldtimeapi.org/timezones
    'aio_username' : '_your_aio_username_',
    'aio_key' : '_your_aio_key_',
    }

Next, set up an Adafruit IO feed named test

We can then have a simple loop for posting data to Adafruit IO without having to deal with connecting or initializing the hardware!

Take a look at your test feed on Adafruit.io and you'll see the value increase each time the CircuitPython board posts data to it!

Feed Setup

If you do not already have an Adafruit IO account set up, head over to io.adafruit.com to link your Adafruit.com account to Adafruit IO.

The first step is to create a new Adafruit IO feed to hold the data from the PyPortal's temperature sensor. Navigate to the feeds page on Adafruit IO. Then click Actions -> Create New Feed, and name this feed weight

Build an Adafruit IO Dashboard

Next, you'll create a dashboard to display the values from the feed you created.

Adding a Gauge Block

To display the values from your Scale, you'll add a gauge block to your dashboard. This blocks displays values within a fixed range and can serve as a visual indication for if the values are too low or high.

From the dashboard you created dashboard, Select the Gauge block.

Select the weight feed

The code will be sending data from the scale in grams.

Set the Block Title to Scale

Set the Gauge Min Value to 0

Set the Gauge Max Value to 500

and Set the Gauge Label to grams

Adding a Line Chart

While displaying the current value of the weight is useful, Adafruit IO stores data so you can monitor how it changes a long period of time. Alternatively, you can visualize it in real-time To do this, we'll use the Line Chart block.

Select the weight feed.

Give the line chart a name, and set it to display live history (you can change to display a longer time period this by editing this block)

Your final dashboard should look like the following:

If you want to customize your dashboard - add more blocks to the dashboard, or resize the existing blocks.

Obtain Adafruit IO Key

You are also going to need your Adafruit IO username and secret API key.

Navigate to your profile and click the View AIO Key button to retrieve them. Write them down in a safe place, you'll need them for the next step.

CircuitPython Library Installation

To interface your PyPortal with the DYMO scale and the internet - you'll need to install the Adafruit CircuitPython Adafruit IO and the Adafruit CircuitPython DymoScale libraries on your PyPortal. 

First make sure you are running the latest version of Adafruit CircuitPython for your board.

Next you'll need to install the necessary libraries to use the hardware--carefully follow the steps to find and install these libraries from Adafruit's CircuitPython library bundle matching your version of CircuitPython. PyPortal requires at least CircuitPython version 4.0.0.

Before continuing make sure your board's lib folder has the following files and folders copied over.

  • adafruit_io
  • adafruit_dymoscale
  • adafruit_esp32spi
  • adafruit_bus_device 
  • adafruit_bitmap_font
  • adafruit_display_text
  • neopixel.mpy

Secrets File Setup

If you have not yet set up a secrets.py file in your CIRCUITPY drive and connected to the Internet using it, follow this guide and come back when you've successfully connected to the internet

Adafruit IO username, and Adafruit IO key. Head to io.adafruit.com and simply click the View AIO Key link on the left hand side of the Adafruit IO page to get this information.

Then, add them to the secrets.py file:

secrets = {
    'ssid' : '_your_wifi_ssid',
    'password : '_your_wifi_password',
    'aio_username' : '_your_adafruit_io_username',
    'aio_key' : '_your_big_huge_super_long_aio_key_'
    }

Add CircuitPython Code and Project Assets

In the embedded code element below, click on the Download: Project Zip link, and save the .zip archive file to your computer.

Then, uncompress the .zip file, it will unpack to a folder named PyPortal_IOT_Scale.

Copy the contents of the PyPortal_IOT_Scale directory to your PyPortal's CIRCUITPY drive.

Make sure to save the fonts (Helvetica-Bold-16.bdf and Helvetica-Bold-36.bdf) into the fonts folder on the CIRCUITPY volume.

"""
PyPortal Smart Scale
an internet of things smart-scale for Adafruit IO

Brent Rubell for Adafruit Industries, 2019
"""
import time
import board
import adafruit_dymoscale
import busio
import digitalio

import displayio
from adafruit_display_text.label import Label
from adafruit_bitmap_font import bitmap_font

from adafruit_esp32spi import adafruit_esp32spi, adafruit_esp32spi_wifimanager
import neopixel
from adafruit_io.adafruit_io import IO_HTTP

# Get wifi details and more from a secrets.py file
try:
    from secrets import secrets
except ImportError:
    print("WiFi secrets are kept in secrets.py, please add them there!")
    raise

# the current working directory (where this file is)
cwd = ("/"+__file__).rsplit('/', 1)[0]
large_font = cwd+"/fonts/Helvetica-Bold-36.bdf"
small_font = cwd+"/fonts/Helvetica-Bold-16.bdf"

root_group = displayio.Group()
print('loading fonts...')
weight_font = bitmap_font.load_font(large_font)
weight_font.load_glyphs(b'0123456789.goz-SCALEROIO ')

text_font = bitmap_font.load_font(small_font)
text_font.load_glyphs(b'sendig!t.')

print('making labels...')
weight_label = Label(weight_font)
weight_label.x = 75
weight_label.y = 120
root_group.append(weight_label)
weight_label.text = "---"

title_label = Label(weight_font)
title_label.x = 65
title_label.y = 20
root_group.append(title_label)
title_label.text = "IO SCALE"

text_label = Label(text_font)
text_label.x = 100
text_label.y = 200
text_label.color = 0xFFFFFF
root_group.append(text_label)

board.DISPLAY.show(root_group)

# PyPortal ESP32 Setup
esp32_cs = digitalio.DigitalInOut(board.ESP_CS)
esp32_ready = digitalio.DigitalInOut(board.ESP_BUSY)
esp32_reset = digitalio.DigitalInOut(board.ESP_RESET)
spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
esp = adafruit_esp32spi.ESP_SPIcontrol(spi, esp32_cs, esp32_ready, esp32_reset)
status_light = neopixel.NeoPixel(board.NEOPIXEL, 1, brightness=0.2)
wifi = adafruit_esp32spi_wifimanager.ESPSPI_WiFiManager(esp, secrets, status_light)

# Set your Adafruit IO Username and Key in secrets.py
# (visit io.adafruit.com if you need to create an account,
# or if you need your Adafruit IO key.)
aio_username = secrets['aio_username']
aio_key = secrets['aio_key']

# Create an instance of the IO_HTTP client
io = IO_HTTP(aio_username, aio_key, wifi)

# Get the weight feed from IO
weight_feed = io.get_feed('weight')

# initialize the dymo scale
units_pin = digitalio.DigitalInOut(board.D3)
units_pin.switch_to_output()
dymo = adafruit_dymoscale.DYMOScale(board.D4, units_pin)

# take a reading of the current time, used for toggling the device out of sleep
time_stamp = time.monotonic()

while True:
    try:
        reading = dymo.weight
        text = "%0.1f g"%reading.weight
        print(text)
        weight_label.text = text
        weight_label.color = 0xFFFFFF
        try:
            print('Sending to Adafruit IO...')
            text_label.text = 'sending...'
            # send data to Adafruit IO (rounded to one decimal place)
            io.send_data(weight_feed['key'], round(reading.weight, 1))
        except (ValueError, RuntimeError) as e:
            print("failed to send data..retrying...")
            wifi.reset()
            continue
        print('Data sent!')
        text_label.text = 'sent!'
        # to avoid sleep mode, toggle the units pin every 2mins.
        if (time.monotonic() - time_stamp) > 120:
            print('toggling units button')
            dymo.toggle_unit_button()
            # reset the time
            time_stamp = time.monotonic()
    except RuntimeError as e:
        weight_label.text = "SCALE\nERROR"
        weight_label.color = 0xFF0000
        print("Error: ", e)

This is what the final contents of the CIRCUITPY drive will look like:

Code Usage

Ensure that the scale's data pin is plugged into D3 on the PyPortal and the units button is plugged into D4 on the PyPortal.

Then, the PyPortal will display IOT Scale and should display the current weight shown on the scale's LCD display.

If your scale is displaying SCALE ERROR, the scale is not turned on yet. Press the power button (the button all the way on the left) to turn on the scale's power.

Since you're not running the scale off of batteries, you'll need to perform this step each time you disconnect/reset the PyPortal.

When you place something on the scale, the PyPortal's display will update with a new value and send it to Adafruit IO.

Every two minutes, the scale's LCD will switch between grams and ounces to avoid going into sleep mode (see the Removing the Auto Shut Off section below) 

Adafruit IO Usage

While the PyPortal can display measurements on its LCD - what if you're physically away from the scale or need to log weight data over a period of time?

How do we know that the weight data is being sent from the PyPortal to Adafruit IO?

Open the Adafruit IO Dashboard you created earlier. Notice that the fill and values of the gauge changes as values are sent from your PyPortal to Adafruit IO.

Then, leave the PyPortal running for a while and come back later to see new data appear on the line graph.

Code Overview

To interface with the DYMO scale's data protocol, we wrote a CircuitPython library called Adafruit CircuitPython DymoScale.

To take a reading from the scale (the library returns the weight in grams), we call

reading = dymo.weight

Then, print out the weight of the reading to the REPL as well as the weight_label on the PyPortal's display:

text = "%0.1f g"%reading.weight
print(text)
weight_label.text = text
weight_label.color = 0xFFFFFF

Now that you have the data from the scale, it is time to send it to Adafruit IO. To do this, the code uses the send_data method from Adafruit IO CircuitPython.

For the weight on your dashboard to reflect what's displayed on the PyPortal the weight sent to IO is rounded to one decimal place.

print('Sending to Adafruit IO...')
text_label.color = 0xFFFFFF
text_label.text = 'Sending...'
# send data to Adafruit IO (rounded to one decimal place)
io.send_data(weight_feed['key'], round(reading.weight, 1))

That's it - sending data to Adafruit IO with CircuitPython is simple!

Removing the Auto Shut Off

The M-series DYMO scales have an automatic shut off "feature". The scale turns off after three minutes of inactivity. While this is a useful feature to preserve the scale's batteries - it causes the scale to turn off if we're measuring anything over a length of three minutes.

If you're measuring the volume of a mug of pour-over coffee or a bag of cat food - the scale will turn off. 

hacks_M10_M25_UserGuide_en-US_pdf.png
Dymo M-Series Manual (http://download.dymo.com/dymo/user-guides/scales/M10_M25_UserGuide_en-US.pdf)

In the Wiring page, you soldered a wire onto the Grams/Ounces button and connected it to your PyPortal. We've included a method in the adafruit_dymoscale library called toggle_unit_button to simulate pressing the button for you.

When the dymo object is initialized in the code, the units_pin is provided to it along with the scale's data pin.

units_pin = digitalio.DigitalInOut(board.D3)
units_pin.switch_to_output()
dymo = adafruit_dymoscale.DYMOScale(board.D4, units_pin)

Then, the code takes a reference time reading with time.monotonic() 

# take a reading of the current time, used for toggling the units button
time_stamp = time.monotonic()

Each time the code runs through the while True loop, we'll check it against the current time. If it exceeds two minutes, the code toggles the unit button (dymo.toggle_unit_button()) and resets the timestamp by setting it to the current time.

# to avoid sleep mode, toggle the units pin every 2 mins.
if (time.monotonic() - time_stamp) > 120:
  print('toggling units button...')
  dymo.toggle_unit_button()
  # reset the time stamp
  time_stamp = time.monotonic()

By performing this toggle, our scale never falls asleep! 

This guide was first published on Apr 02, 2019. It was last updated on Apr 02, 2019.