knurling-rs / knurling-session-20q4

Building your own embedded CO2 measuring device. With Rust!

Knurling Session 2020 Q4

This repo contains the source for the first knurling session as well as the example code.

About

This course will cover building a CO2 measuring device. We will show how to start an embedded program from scratch, how to write a driver for the sensor, and how to read the sensor output in a terminal. We will build a visual indicator for air quality and an acoustic alarm. In the last part, we will add an ePaper display to the setup and talk bit about the embedded-graphics crate.

Read it

You can access a rendered version at

session20q4.ferrous-systems.com

To build from source just run (assuming you have mdbook installed):

$ mdbook serve

Example code

Example code can be found in code/.

Contributing

Please open an issue if you get stuck or find anything to improve this book!

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be licensed as below, without any additional terms or conditions.

Support

The knurling sessions is part of the Knurling project, Ferrous Systems' effort at improving tooling used to develop for embedded systems.

If you think that our work is useful, consider sponsoring it via GitHub Sponsors.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

knurling-session-20q4's Issues

It might be a good idea to include how to revert driver mod by Zadig

It requires a bit of an inconvenient investigation to find out the reason for Nordic nRF Command Line tools don't work after the driver was modified by Zadig.

The steps are:

• Go to the Device Manager
• Find the USB device named BULK Interface
• Right click on it, select update driver
• Select Browse my computers for drivers
• Select Let me pick from a list of available drivers on my computer
• The list will have "J-Link driver" select that and click Next.

Display flashing when updated

Hi knurling-rs team!

First off, thank you for making this tutorial. It was interesting, informative, and easy to follow.

At the end of the section on displaying sensor data, there's a mention that: "The display still flashes when it is updated, this and other more aesthetic issues will be addressed in the last update of this project, delivered in January."

Any word on resolving those issues or recommendations about how to stop the display flashing?

Thanks a lot

Link to code on Github is broken

Link such as:

[3_temperature.rs](https://github.com/knurling-rs/knurling-sessions-20q4/blob/main/src/bin/3_temperature.rs).

in file https://github.com/knurling-rs/knurling-session-20q4/blob/main/src/sessions/internal_temp.md
are broken. I couldn't find the actual source file to correct it myself.

Wrong pin type for SCL and SDA on the SCD30 examples

The code in the SCD30 examples for declaring the SCL and SDA pins does not compile as is with the latest cargo packages. I am not completely sure if the hal version changed or not, but Twim::Pins require a floating input instead of a disconnected one.

That is:

pins.p0_30.into_floating_input().degrade();

Instead of:

pins.p0_30.degrade();

defmt issue when crate name starts with number

defmt does not work when the crate name starts with a number (e.g. 01_hello_extended.rs). I used the app template generator as suggested in the Knurling-session-20q4.

Dependencies used in Cargo.toml:

[dependencies]
nrf52840-hal = "0.15.1"
embedded-hal = "0.2.7"
cortex-m = "0.7.6"
cortex-m-rt = "0.7.1"
defmt = "0.3.2"
defmt-rtt = "0.3.2"
panic-probe = { version = "0.3.0", features = ["print-defmt"] }
nb = "1.0.0"
crc_all = "0.2.2"

Update example code to defmt 0.2

Wrong preparations chapter for Session 20q4?

It seems like something has gone wrong in the book with the Preparations chapter for the CO2 sensor session here: https://github.com/knurling-rs/knurling-session-20q4/blob/main/src/sessions/Preparations.md

This looks a lot more like the shopping list for the 21q1 Minesweeper session?

Differet product id in the udev rule

Installation instructions say to add an udev rule with a ATTRS{idProduct}=="1015"

knurling-session-20q4/src/sessions/installation.md

Line 63 in e36b9d9

ATTRS{idVendor}=="1366", ATTRS{idProduct}=="1015", TAG+="uaccess"

However, this doesn't work for my nRF52840 Development because its product id is 1051

❯ lsusb | grep SEGGER
Bus 002 Device 004: ID 1366:1051 SEGGER J-Link

So either there are development kits out there with different product ids, or 1015 is a typo. But seeing how consistent its use is throughout the book (and here knurling-rs/probe-run#220), it seems to me that there indeed must be devkits out there with different product ids?

In either case, imo, this should be reflected in the book (also in the other places that mention that id). I spent way too much time trying to figure out what's wrong, not seeing that the 1015 and 1051 values don't match.

Wrong circuit diagram for CA RGB LED

The circuit diagram in https://github.com/knurling-rs/knurling-session-20q4/blob/main/src/img/knurling-rgb-led-ca-circuit.png shown a common cathode LED, and not a common anode one.

The three LEDs should be reversed for the diagram to be correct.

link more prominently to this repository from the book

I was reading through the first pages of https://session20q4.ferrous-systems.com but didn't see any link to this repository where the starter code is.

On one of those few first pages we should indicate that should clone / fetch this repository because it contains the starter code.
cc @Urhengulas