[roll third_party/pigweed] pw_chrono_rp2040: Minor tweaks to documentation and test

Surfaces more information about when to use this pw_chrono backend. Also
updates the test to poll now() rather than doing arbitrary work to
hopefully be less likely to be prone to flake (not that any flakes were
observed with the old test design).

Original-Fixes: b/303297807
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/183730

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: e982c93aba2cc25..e8de610d576dd4a
Roller-URL: https://ci.chromium.org/b/8755911799198176417
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I7daf85b88ace92eb11c8b27b01b7a2b54e7eac82
Reviewed-on: https://pigweed-review.googlesource.com/c/example/echo/+/192874
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
1 file changed
tree: 02dbde05649ffa868439589a52572dc7aae808e6
  1. src/
  2. targets/
  3. third_party/
  4. tools/
  5. .bazelrc
  6. .bazelversion
  7. .gitignore
  8. .gitmodules
  9. BUILD.bazel
  10. echo.bzl
  11. README.md
  12. requirements.in
  13. requirements_lock.txt
  14. WORKSPACE
README.md

Pigweed: minimal Bazel example

This repository contains a minimal example of a Bazel-based Pigweed project. It's an echo application for the STM32F429 Discovery Board.

Cloning

git clone --recursive https://pigweed.googlesource.com/example/echo

If you already cloned but forgot to include --recursive, run git submodule update --init to pull all submodules.

TODO: b/300695111 - Don't require submodules for this example.

Building

We‘ll assume you already have Bazel on your system. If you don’t, the recommended way to get it is through Bazelisk.

To build the entire project (including building the application for both the host and the STM32 Discovery Board), run

bazel build //...

To run the application locally on your machine, run,

bazel run //src:echo

Flashing

To flash the firmware to a STM32F429 Discovery Board connected to your machine, run,

bazel run //tools:flash

Note that you don't need to build the firmware first: Bazel knows that the firmware images are needed to flash the board, and will build them for you. And if you edit the source of the firmware or any of its dependencies, it will get rebuilt when you flash.

Communicating

Run,

bazel run //tools:miniterm -- /dev/ttyACM0 --filter=debug

to communicate with the board. When you transmit a character, you should get the same character back!