When using Microsoft Azure services, it's helpful to know how much you're spending on a day-to-day basis. This Azure cost monitor uses the low-power, wireless Adafruit MagTag board to display a daily cost forecast for your Azure subscription.*

This project is intended to show you how to use the Azure cost management API. Take a look at this project and adapt it to fit your needs!

Please note that it's only possible to get a cost forecast -- actual costs are only available once you're billed.


MagTag dev board with enclosure pieces, four magnet feet, and lipoly battery
The Adafruit MagTag combines the new ESP32-S2 wireless module and a 2.9" grayscale E-Ink display to make a low-power IoT display that can show data on its screen...
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Angled shot of Adafruit MagTag development board with ESP32-S2 and E-Ink display.
The Adafruit MagTag combines the new ESP32-S2 wireless module and a 2.9" grayscale E-Ink display to make a low-power IoT display that can show data on its screen even when power...
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USB Type A to Type C Cable - approx 1 meter / 3 ft long
As technology changes and adapts, so does Adafruit. This  USB Type A to Type C cable will help you with the transition to USB C, even if you're still...
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The way we'll get the cost forecast of your Azure subscription is by registering an application on Azure. This allows you to make REST API calls directly from the MagTag using secure credentials. To do this you'll create a Service Principal using the Azure CloudShell.

1. Log into the Azure portal

2. Click on the CloudShell icon as shown in the photo above.

If this is the first time you're using CloudShell you'll need to select a storage account to use it with.

Note: using a storage account for this project costs <$0.01 a day.

For more info on CloudShell visit this site.

3. Once the CLI loads type and run:

az ad sp create-for-rbac --name [APP_NAME]

Replace "[APP_NAME]" with a name like "cost-monitor"

4. Save Credentials

Copy the APP ID, PASSWORD, and TENANT ID and save into a secure location. We'll need this later for the MagTag's secrets.py file.

5. Get Subscription ID property

Next type and run:

az account list

Again, copy and save the "id" property together with the credentials from the previous step. Label this property SUBSCRIPTION ID. We'll use it later in the secrets.py file.

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 drive to iterate.

Set Up CircuitPython

Follow the steps to get CircuitPython installed on your MagTag.

Click the link above and download the latest .BIN and .UF2 file

(depending on how you program the ESP32S2 board you may need one or the other, might as well get both)

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

Plug your MagTag 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.

Option 1 - Load with UF2 Bootloader

This is by far the easiest way to load CircuitPython. However it requires your board has the UF2 bootloader installed. Some early boards do not (we hadn't written UF2 yet!) - in which case you can load using the built in ROM bootloader.

Still, try this first!

Try Launching UF2 Bootloader

Loading CircuitPython by drag-n-drop UF2 bootloader is the easier way and we recommend it. If you have a MagTag where the front of the board is black, your MagTag came with UF2 already on it.

Launch UF2 by double-clicking the Reset button (the one next to the USB C port). You may have to try a few times to get the timing right.

If the UF2 bootloader is installed, you will see a new disk drive appear called MAGTAGBOOT

Copy the UF2 file you downloaded at the first step of this tutorial onto the MAGTAGBOOT drive

If you're using Windows and you get an error at the end of the file copy that says Error from the file copy, Error 0x800701B1: A device which does not exist was specified. You can ignore this error, the bootloader sometimes disconnects without telling Windows, the install completed just fine and you can continue. If its really annoying, you can also upgrade the bootloader (the latest version of the UF2 bootloader fixes this warning)

Your board should auto-reset into CircuitPython, or you may need to press reset. A CIRCUITPY drive will appear. You're done! Go to the next pages.

Option 2 - Use esptool to load BIN file

If you have an original MagTag with while soldermask on the front, we didn't have UF2 written for the ESP32S2 yet so it will not come with the UF2 bootloader.

You can upload with esptool to the ROM (hardware) bootloader instead!

Follow the initial steps found in the Run esptool and check connection section of the ROM Bootloader page to verify your environment is set up, your board is successfully connected, and which port it's using.

In the final command to write a binary file to the board, replace the port with your port, and replace "firmware.bin" with the the file you downloaded above.

The output should look something like the output in the image.

Press reset to exit the bootloader.

Your CIRCUITPY drive should appear!

You're all set! Go to the next pages.

Option 3 - Use Chrome Browser To Upload BIN file

If for some reason you cannot get esptool to run, you can always try using the Chrome-browser version of esptool we have written. This is handy if you don't have Python on your computer, or something is really weird with your setup that makes esptool not run (which happens sometimes and isn't worth debugging!) You can follow along on the Web Serial ESPTool page and either load the UF2 bootloader and then come back to Option 1 on this page, or you can download the CircuitPython BIN file directly using the tool in the same manner as the bootloader.

One of the great things about the ESP32 is the built-in WiFi capabilities. This page covers the basics of getting connected using CircuitPython.

The first thing you need to do is update your code.py to the following. Click the Download Project Bundle button below to download the necessary libraries and the code.py file in a zip file. Extract the contents of the zip file, and copy the entire lib folder and the code.py file to your CIRCUITPY drive.

# SPDX-FileCopyrightText: 2020 Brent Rubell for Adafruit Industries
# SPDX-License-Identifier: MIT

import os
import ipaddress
import ssl
import wifi
import socketpool
import adafruit_requests

# URLs to fetch from
TEXT_URL = "http://wifitest.adafruit.com/testwifi/index.html"
JSON_QUOTES_URL = "https://www.adafruit.com/api/quotes.php"
JSON_STARS_URL = "https://api.github.com/repos/adafruit/circuitpython"

print("ESP32-S2 WebClient Test")

print(f"My MAC address: {[hex(i) for i in wifi.radio.mac_address]}")

print("Available WiFi networks:")
for network in wifi.radio.start_scanning_networks():
    print("\t%s\t\tRSSI: %d\tChannel: %d" % (str(network.ssid, "utf-8"),
                                             network.rssi, network.channel))

print(f"Connecting to {os.getenv('CIRCUITPY_WIFI_SSID')}")
wifi.radio.connect(os.getenv("CIRCUITPY_WIFI_SSID"), os.getenv("CIRCUITPY_WIFI_PASSWORD"))
print(f"Connected to {os.getenv('CIRCUITPY_WIFI_SSID')}")
print(f"My IP address: {wifi.radio.ipv4_address}")

ping_ip = ipaddress.IPv4Address("")
ping = wifi.radio.ping(ip=ping_ip)

# retry once if timed out
if ping is None:
    ping = wifi.radio.ping(ip=ping_ip)

if ping is None:
    print("Couldn't ping 'google.com' successfully")
    # convert s to ms
    print(f"Pinging 'google.com' took: {ping * 1000} ms")

pool = socketpool.SocketPool(wifi.radio)
requests = adafruit_requests.Session(pool, ssl.create_default_context())

print(f"Fetching text from {TEXT_URL}")
response = requests.get(TEXT_URL)
print("-" * 40)
print("-" * 40)

print(f"Fetching json from {JSON_QUOTES_URL}")
response = requests.get(JSON_QUOTES_URL)
print("-" * 40)
print("-" * 40)


print(f"Fetching and parsing json from {JSON_STARS_URL}")
response = requests.get(JSON_STARS_URL)
print("-" * 40)
print(f"CircuitPython GitHub Stars: {response.json()['stargazers_count']}")
print("-" * 40)


Your CIRCUITPY drive should resemble the following.


To get connected, the next thing you need to do is update the settings.toml file.

The settings.toml 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 settings.toml file, that is on your CIRCUITPY drive, to hold secret/private/custom data. That way you can share your main project without worrying about accidentally sharing private stuff.

If you have a fresh install of CircuitPython on your board, the initial settings.toml file on your CIRCUITPY drive is empty.

To get started, you can update the settings.toml on your CIRCUITPY drive to contain the following code.

# SPDX-FileCopyrightText: 2023 Adafruit Industries
# SPDX-License-Identifier: MIT

# This is where you store the credentials necessary for your code.
# The associated demo only requires WiFi, but you can include any
# credentials here, such as Adafruit IO username and key, etc.
CIRCUITPY_WIFI_SSID = "your-wifi-ssid"
CIRCUITPY_WIFI_PASSWORD = "your-wifi-password"

This file should contain a series of Python variables, each assigned to a string. Each variable should describe what it represents (say wifi_ssid), followed by an (equals sign), followed by the data in the form of a Python string (such as "my-wifi-password" including the quote marks).

At a minimum you'll need to add/update your WiFi SSID and WiFi password, so do that now!

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.

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 settings.toml - keep that out of GitHub, Discord or other project-sharing sites.

Don't share your settings.toml file! It has your passwords and API keys in it!

If you connect to the serial console, you should see something like the following:

In order, the example code...

Checks the ESP32's MAC address.

print(f"My MAC address: {[hex(i) for i in wifi.radio.mac_address]}")

Performs a scan of all access points and prints out the access point's name (SSID), signal strength (RSSI), and channel.

print("Available WiFi networks:")
for network in wifi.radio.start_scanning_networks():
    print("\t%s\t\tRSSI: %d\tChannel: %d" % (str(network.ssid, "utf-8"),
                                             network.rssi, network.channel))

Connects to the access point you defined in the settings.toml file, and prints out its local IP address.

print(f"Connecting to {os.getenv('WIFI_SSID')}")
wifi.radio.connect(os.getenv("WIFI_SSID"), os.getenv("WIFI_PASSWORD"))
print(f"Connected to {os.getenv('WIFI_SSID')}")
print(f"My IP address: {wifi.radio.ipv4_address}")

Attempts to ping a Google DNS server to test connectivity. If a ping fails, it returns None. Initial pings can sometimes fail for various reasons. So, if the initial ping is successful (is not None), it will print the echo speed in ms. If the initial ping fails, it will try one more time to ping, and then print the returned value. If the second ping fails, it will result in "Ping google.com: None ms" being printed to the serial console. Failure to ping does not always indicate a lack of connectivity, so the code will continue to run.

ping_ip = ipaddress.IPv4Address("")
ping = wifi.radio.ping(ip=ping_ip) * 1000
if ping is not None:
    print(f"Ping google.com: {ping} ms")
    ping = wifi.radio.ping(ip=ping_ip)
    print(f"Ping google.com: {ping} ms")

The code creates a socketpool using the wifi radio's available sockets. This is performed so we don't need to re-use sockets. Then, it initializes a a new instance of the requests interface - which makes getting data from the internet really really easy.

pool = socketpool.SocketPool(wifi.radio)
requests = adafruit_requests.Session(pool, ssl.create_default_context())

To read in plain-text from a web URL, call requests.get - you may pass in either a http, or a https url for SSL connectivity. 

print(f"Fetching text from {TEXT_URL}")
response = requests.get(TEXT_URL)
print("-" * 40)
print("-" * 40)

Requests can also display a JSON-formatted response from a web URL using a call to requests.get

print(f"Fetching json from {JSON_QUOTES_URL}")
response = requests.get(JSON_QUOTES_URL)
print("-" * 40)
print("-" * 40)

Finally, you can fetch and parse a JSON URL using requests.get. This code snippet obtains the stargazers_count field from a call to the GitHub API.

print(f"Fetching and parsing json from {JSON_STARS_URL}")
response = requests.get(JSON_STARS_URL)
print("-" * 40)
print(f"CircuitPython GitHub Stars: {response.json()['stargazers_count']}")
print("-" * 40)

OK you now have your ESP32 board set up with a proper settings.toml file and can connect over the Internet. If not, check that your settings.toml file has the right SSID and password and retrace your steps until you get the Internet connectivity working!

To use all the amazing features of your MagTag with CircuitPython, you must first install a number of libraries. This page covers that process.

Get Latest Adafruit CircuitPython Bundle

Download the Adafruit CircuitPython Library Bundle. You can find the latest release here:

Download the adafruit-circuitpython-bundle-version-mpy-*.zip bundle zip file, and unzip a folder of the same name. Inside you'll find a lib folder. The entire collection of libraries is too large to fit on the CIRCUITPY drive. Therefore, you'll need to copy the necessary libraries to your board individually.

At a minimum, the following libraries are required. Copy the following folders or .mpy files to the lib folder on your CIRCUITPY drive. If the library is a folder, copy the entire folder to the lib folder on your board.

Library folders (copy the whole folder over to lib):

  • adafruit_magtag - This is a helper library designed for using all of the features of the MagTag, including networking, buttons, NeoPixels, etc.
  • adafruit_portalbase - This library is the base library that adafruit_magtag is built on top of.
  • adafruit_bitmap_font - There is fancy font support, and it's easy to make new fonts. This library reads and parses font files.
  • adafruit_display_text - This library displays text on the screen.
  • adafruit_io - This library helps connect the MagTag to our free data logging and viewing service
  • adafruit_minimqtt - This library provides MQTT service for Adafruit IO.

Library files:

  • adafruit_requests.mpy - This library allows us to perform HTTP requests and get responses back from servers. GET/POST/PUT/PATCH - they're all in here!
  • adafruit_fakerequests.mpy  - This library allows you to create fake HTTP requests by using local files.
  • adafruit_miniqr.mpy  - QR creation library lets us add easy-to-scan 2D barcodes to the E-Ink display
  • neopixel.mpy - This library is used to control the onboard NeoPixels.
  • simpleio.mpy - This library is used for tone generation.


Even if you aren't planning to go online with your MagTag, you'll need to have a secrets.py file in the root directory (top level) of your CIRCUITPY drive. If you do not intend to connect to wireless, it does not need to have valid data in it. Here's more info on the secrets.py file.

You will need a few other libraries not previously loaded. Compare the following list against your previous uploaded directories into CIRCUITPY/lib and add the remaining necessary ones.


  • adafruit_bitmap_font
  • adafruit_bus_device
  • adafruit_display_text
  • adafruit_io
  • adafruit_magtag
  • adafruit_portalbase
  • adafruit_rsa
  • adafruit_binascii.mpy
  • adafruit_fakerequests.mpy
  • adafruit_logging.mpy
  • adafruit_miniqr.mpy
  • adafruit_pyportal.mpy
  • adafruit_requests.mpy
  • neopixel.mpy
  • simpleio.mpy


For this project, we recommend using VS Code with the CircuitPython extension

Once you've configured your coding workspace, grab the Azure Cost Monitor program code by cloning the GitHub repo (direct link here) onto your computer:

git clone https://github.com/microsoft/azure-cost-monitor.git

Create a secrets.py file

This is where we'll store our WiFi and Azure credentials (all that stuff we copied from earlier!)

1. Create a new file called secrets.py

2. Fill secrets.py with the following code: 

secrets = {
  "ssid" : "YOUR_WIFI_SSID",
  "password" : "YOUR_WIFI_PASSWORD",
  "appId": "AZURE_APP_ID",
  "clientSecret": "PASSWORD",
  "tenant": "TENANT_ID",
  "subscription": "SUBSCRIPTION_ID

3. Replace all of the variables in quotes (e.g. "YOUR_WIFI_SSID") with the appropriate credentials for your WiFi SSID and password, and the Azure credentials you copied from the "Get Azure Credentials" section.

Keep your secrets.py private! Do not upload it to GitHub, etc.

If you create a repo or otherwise share your project, be sure to leave out this file.

Load files onto the MagTag!

We're ready to go! To finish up, we just need to load three files onto the MagTag:

Note: azure.py and code.py are in the src folder of the GitHub repo

  • secrets.py
    • This holds our credentials
  • azure.py
    • This interfaces with Microsoft Azure Cost API
  • code.py
    • This is the main program loop!

Wait.. what's happening??

The azure.py file is a mini-library for interfacing with the Azure Cost API. It creates a class called 'azure' which takes in your Azure credentials (which we pull from the secrets.py file). The cost_forecast function grabs and returns your Azure daily cost forecast. If you want to see more info, use the following command at the bottom of the cost_forecast function:


The code.py file is the main program loop: it loads the secrets.py file, connects to your local WiFi network, and then connects Azure and returns the daily cost forecast once every 24 hours. 

If you want to see more info or if you need to debug, use a Serial Monitor (e.g. PuTTY). Here's a great overview on how to do this on Windows.

Going Further: Modify or add to other projects

One of the main reasons we created the azure.py file was to make it easier to add cost tracking to other projects.

The Azure Cost API allows you to monitor a subscription or, with a bit of modification, a specific resource group. See this resource for assistance on changing the API request to monitor a resource group.

Other helpful modifications might be:

  • Add a datestamp to the print output
  • Create an estimate of aggregated cost forecast
    • Keep in mind that your forecasted cost will likely be different than actual billed costs
  • Set the NeoPixels to change color based on the cost forecast
    • For example, red could indicate that cost is above an expected threshold (e.g. if you're expecting less than $0.20/day, turn NeoPixels red if forecast cost is above that)
  • Other thoughts? Let us know by opening an issue in the GitHub repo!

Connect the battery to the MagTag, screw in the magnetic feet, and display in a convenient location.

The main program loop will update once every 24 hrs, so the battery should last a few weeks. When you need to charge, just plug in a USBC cable to the MagTag and it will charge the battery!

When battery is being charged, the yellow LED on bottom left will light up.

Happy making, friends!

This guide was first published on Feb 15, 2021. It was last updated on Jun 11, 2024.