14. Run the air quality monitor app#

Caution

This section and the ones after it require a Pimoroni Enviro+ Pack. See Set up your hardware for a review of the hardware setup options. If you don’t have an Enviro+, skip ahead to 16. Wrapping up to wrap up your tutorial experience.

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.

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 Build Targets expand //apps/production, then right-click :flash (alias), then select Run target.

$ bazelisk run //apps/production:flash

You should see output like this:

INFO: Analyzed target //apps/production:flash (2 packages loaded, 84 targets configured).
INFO: Found 1 target...
Target //apps/production:flash_rp2040 up-to-date:
  bazel-bin/apps/production/flash_rp2040.exe
INFO: Elapsed time: 0.311s, Critical Path: 0.04s
INFO: 1 process: 1 internal.
INFO: Build completed successfully, 1 total action
INFO: Running command line: bazel-bin/apps/production/flash_rp2040.exe apps/production/rp2040.elf
20240805 18:35:58 INF Only one device detected.
20240805 18:35:58 INF Flashing bus 3 port 6

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 Build Targets expand //apps/production, then right-click :rp2040_console (native binary) (if you want to run the terminal-based console) or :rp2040_webconsole (native_binary) (if you want to run the web-based console), then select Run target.

Run the terminal-based console:

$ bazelisk run //apps/production:rp2040_console

Or the web-based console:

$ bazelisk run //apps/production:rp2040_webconsole

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.

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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