14. Run the air quality monitor app#

Your tour of Pigweed is almost done. Before you go, let’s get you familiar with the application described at Sense, the product concept. Within the Sense codebase this app is called production. The purpose of the production app is to demonstrate what a medium-complexity application built on top of Pigweed’s software abstractions looks like. We’re still perfecting the codebase structure, but this application can begin to give you an idea of how the Pigweed team thinks Pigweed-based projects should be structured.

Important

This section requires the full hardware setup.

First, let’s get the app running on your Pico. Then we’ll provide an overview of the code.

Warning

This is just a sample application. It is not suitable for real air quality monitoring.

Set up your hardware#

This part of the tutorial requires the full setup.

Flash the Pico#

Flash the production app to your Pico:

In Bazel Targets expand //apps/production, then right-click :flash_rp2040 (native binary), then select Run target.

In Bazel Targets expand //apps/production, then right-click :flash_rp2350 (native binary), then select Run target.

bazelisk run //apps/production:flash_rp2040

bazelisk run //apps/production:flash_rp2350

Monitor the app’s logs#

The app prints out a lot of informational logs. These logs can help you grok how the app works. Fire up pw_console again now:

In Bazel Targets right-click the :rp2040_console (native binary) target (under //apps/production) then select Run target.

In Bazel Targets right-click the :rp2350_console (native binary) target (under //apps/production) then select Run target.

Run the terminal-based console:

bazelisk run //apps/production:rp2040_console

bazelisk run //apps/production:rp2350_console

See 6. Run the host app if you need a refresher on how to use pw_console.

Trigger an air quality alarm#

The default mode of the app is to continuously monitor air quality. You should see the LED on your Enviro+ in one of the following states:

  • Blue/green: Excellent air quality

  • Green: Good air quality

  • Orange: Meh air quality

  • Red: Bad air quality

Troubleshooting

The LCD screen is blank. This is expected because we haven’t implemented display support in the app yet. Stay tuned!

Try triggering an air quality alarm now:

  1. Hold a strong chemical such as rubbing alcohol close to the BME688 sensor on your Enviro+ Pack.

    The LED on the Enviro+ Pack should change to orange (meh air quality) or red (bad air quality).

The next video is an example of what you should see.

Adjust the alarm sensitivity#

You can adjust the sensitivity i.e. thresholds of the alarm with the A and B buttons on your Enviro+ Pack:

  • Press the A button repeatedly to increase the sensitivity of the alarm. In other words, with only a slight change in air quality the LED will shift to orange (meh air quality) or red (bad air quality).

  • Press the B button repeatedly to decrease the sensitivity of the alarm. In other words, it takes a bigger change in air quality for the LED to shift to orange or red.

Note

The “threshold adjustment” mode that you enter after pressing A or B will automatically exit after 3 seconds of inactivity.

In the Device Logs of pw_console you should see the air quality thresholds change as you press A and B. For example, if you quickly press A twice (i.e. in less than a second) you should see a log like this:

19:38:23  INF  00:00:25.758  STATE  Air quality thresholds set: alarm at 384, silence at 512

That log is telling you that the LED will change to red and start blinking when the air quality value is less than 384.

View more information in the custom web app#

Now that your Pico is running the full production app, the custom web app that was demonstrated in 11. Communicate with your Pico over the Web Serial API will show you more information if you fire it up again.

Code overview#

As mentioned in the intro of this page, the production app provides a good start for figuring out how to structure your Pigweed-based project. It’s not perfect yet, but it’s a solid start. We’ll leave it up to you to study the code in-depth, but here are some pointers on the relevant parts of the Sense codebase:

  • //apps/production/*: The app’s entrypoint code.

  • //modules/*: Portable business logic, algorithms, state handling, etc. Look at the header includes in //apps/production/main.cc to figure out what modules to study.

  • //system/*: System global accesors. Gives access to pre-created instances of portable system interfaces. For example, am::system::RpcServer() returns the RPC server instance.

Summary#

You now have a rudimentary but working air quality monitor. More importantly, the code that powers your new air quality monitor is a solid (but not perfect) starting point for learning how to structure your own Pigweed-powered products.

Next, head over to 15. Handle crashes and view snapshots to learn about the pigweed crash handler and crash snapshots.

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