arduino-lightfx

LightFX Arduino code repository for LED strips using WS2811 chip - light effects tailored to my house setup.

Dev Env

Tools

• Install Python 3.11
  • On Windows: Go to MS Store and look for Python 3.11 application. Install it as any other store app
• Install PlatformIO Core (CLI)
  • Follow instructions in the docs - I used the local download approach. Use what makes sense for your platform.
• Install an IDE
  • CLion is a great one - however, commercial product (but REALLY Great)
  • VS Code is a great for someone starting with PlatformIO - recommended by the team. Freeware.

Setup

To create a new project, follow the instructions on PlatformIO site about getting started. There is great documentation about integrations with IDEs, capabilities and configuration needed of supported boards (Arduino, Raspberry Pi, ESP32, etc).

Overview

This project started as Arduino IDE based, then as number of files grew moved over to PlatformIO and CLion.

The backbone of controlling the LEDs is the FastLED library. Several light effects are original, many others are inspired from great example repositories (many thanks to their respective owners for sharing - it has helped me learn a LOT!):

• https://github.com/atuline/FastLED-Demos
• https://github.com/atuline/FastLED-SoundReactive
• https://github.com/chemdoc77
• https://github.com/marmilicious
• https://github.com/marcmerlin
• https://github.com/davepl/DavesGarageLEDSeries
• https://github.com/s-marley/FastLED-basics
• https://github.com/AaronLiddiment
• https://github.com/evilgeniuslabs
• https://github.com/jasoncoon
• https://github.com/brimshot/quickPatterns

Board

The target board is an Arduino Nano RP 2040 Connect feature packed and powerful in a small package - built around dual core Raspberry Pi 2040 microcontroller. It sports a Wi-Fi module that has been leveraged to host a little web-server to aid in configuring the light effects.

The Nano RP2040 board has a built-in PDM microphone, which has been enabled as a source of entropy for the random number generator - the PDM library takes about 20% of the board's available RAM (264kB) for the audio signal processing. Overall, this program uses about 40% of the available RAM - the other 20% are consumed by the OS, FastLED and light effects data.

PIO availability helps a lot with FastLED library performance and effects consistent timings - creating and outputting the PWM signal for controlling the LEDs does not take main CPU cycles and is handled in the background.

The RP2040 chip overall computing power (two ARM cores @ 133MHz) and RAM are leveraged by the design in engaging features that might be challenging for a lesser configuration:

• multithreading
• regular expression matching
• array manipulation
• sound processing
• complex math
• file system
• web connectivity
  • web server, JSON REST API
  • NTP connection for time sync

Note the code is not designed with portability in mind - quite the opposite, it targets Nano RP2040 board and its resources specifically. This avoids code & design complexity and employs a good amount of power reserve for other tasks or more complex lighting effects. It is acknowledged that it sacrifices portability.

Design

The system is designed as a platform that hosts a number of light effects, has awareness of time and holiday in effect, and changes the current light effect on few criteria. Each light effect is encapsulated in a subclass of a base abstract class that defines the API. At bootstrap, each effect auto-registers itself into the global light effects registry in order to make itself available.

The time awareness gives several benefits:

• auto-detection of holiday (based on day/month) that drives the color palettes appropriate for the occasion
• dimming rules for the time of day (brightness reduction of the LED strip, as we head further into the night)

Multi-threading

Several dedicated threads are defined in the system:

• Main thread runs the Web Server
  • as the Web Server implements REST-ful API using JSON data format, the Arduino JSON library needed more memory allocated for a dedicated thread. On the main thread, however, no special memory provisions were needed - hence it was left running there.
• Thread 0 runs the light effects
• Thread 1 runs the microphone signal processing (PDM to PCM conversion)

Configuration

A single LED controller is instantiated from FastLED library that runs on pin 25 (aka pin D2 on the pinout diagram) for PWM output. The number of pixels configured in the system is 384 - this drives memory allocation for pixel arrays. The LED strip installed on the house are connected in a graph with the longest path at about 300 pixels. For WS2811 LED strips - running at 12V - a pixel consists of 3 LEDs.

I have used LED strips with a LED density of 30 LED/m - made by BTF-Lighting (part number WS28115M30LW65 on Amazon) - outdoor splash proof rated IP65.

Board wrapper

Nano RP2040 Connect board operates internally at 3.3V, whereas the WS2811 LED strips operate with 12V for main power and 5V for command pin (5V for data/command is unconfirmed by the datasheet, experimentally it has been proven to work) - hence a LED driver circuit surrounds the board.

It uses the main 12V power supplied to the LED strips to scale it down to 5V (LM7805) in order to provide the board with power (note the Arduino board has its own voltage regulator onboard, which makes it accept external power from 5V to 21V, per the specs). The PWM 3.3V signal is run through a level shifter (74HCT125) to 5V for the LED command driver.

This way, a single 3 pin connector is used to connect the board to the LED strip as its controller - it takes 12V power from the strip and supplies PWM 5V signal to the LEDs control pin.

The electronic schematic and PCB designs can be found as EasyEDA project.

C++ standard

The current Arduino libraries are leveraging the C++ 14 standard, hence the code can be written with this standard level in mind and IDE support can be configured accordingly (if needed).

The confirmation of which C++ standard is currently in use comes from a verbose build with PlatformIO - pio run -v after a clean. Inspect the compiler -std=xyz argument. For instance, -std=gnu++14 indicates C++ 14 standard is used.

Please see C++ 14 reference for standard details.

Debug

Overview

The debugging with Arduino Nano RP2040 Connect board is still very much work in progress and not very stable. The steps below deviate from the mainstream of installing tools/packages out of the box and just work - as either more updates are made to the tools/packages, or I manage to put together a pull-request, etc. we'll eventually get back on mainstream.

The main issues worked around:

• OpenOCD debugger has no support for the flash chip on-board - Atmel AT25SF128A 16MB NOR Flash
• OpenOCD configuration scripts need tweaks in order to work with RaspberryPi Debug Probe and Serial Wire Debugging (SWD)
• Some libraries (e.g. FastLED) do not compile well in debug build configuration
• Platform does not compile well using latest toolchain in debug configuration

Hardware Pre-Requisites

The Raspberry Pi Debug Probe is needed along with a couple of extra JST SH 3-pin SWD cables. The Nano RP2040 board needs some soldering work to connect wires to the SWD pads on the back and make those available through a connector. Be very careful with the SWD pads - they are very fragile and can easily break and come off the PCB.

The debug serial port wires can be soldered directly onto the header respective pins.

Raspberry Pi Debug Probe documentation is a good help to get started.

Custom OpenOCD build

Assumptions:

• the code base is located at ~/Code/Arduino/repos/arduino-lightfx on the Ubuntu machine
• the custom tools folder exists at ~/Code/Tools
• current working folder is ~/Code/Arduino/repos/arduino-lightfx

From Earle Philhower's Pico Quick Toolchain download the latest OpenOCD tool (file aarch64-linux-gnu.openocd-4d87f6dca.230911.tar.gz for Ubuntu) - as of this writing, the latest is version 2.1.0-a from Sep 11, 2023.

Decompress this archive to ~/Code/Tools/openocd-rp2040-earle folder.

Note: It is also worth checking the platformio registry for Earle Philhower's OpenOCD for RP2040 - check the published date (hover over it with mouse). For instance, as of this writing, the version on PlatformIO is from Feb 18, 2023 (version 5.100300.230216)

Clone the OpenOCD git repository for RP2040 and switch to branch rp2040-v0.12.0:

git clone git@github.com/raspberrypi/openocd.git; git switch rp2040-v0.12.0

In a code editor - VSCode - locate and open the file ./src/flash/nor/spi.c. Insert the following line into flash_devices array:

FLASH_ID("atmel 25sf128a", 0x03, 0xeb, 0x02, 0xd8, 0xc7, 0x0001891f, 0x100, 0x1000, 0x1000000), //Arduino Nano Connect RP2040

Build the code - follow the instructions to install dependencies needed. First time there are few extra commands to be run, afterward only run make:

cd openocd
./bootstrap
./configure
make

Copy/replace the openocd executable to the openocd package in your home folder:

cp ./src/openocd ~/Code/Tools/openocd-rp2040-earle/bin

Platformio Debug Config

As indicated by the platform config file - ~/.platformio/platforms/raspberrypi/platform.json - the OpenOCD package listed as a dependency is indicated below:

"tool-openocd-raspberrypi": {
      "type": "uploader",
      "optional": true,
      "owner": "platformio",
      "version": "~2.1100.0"
    }

Ensure you have the arduino-lightfx repository open in VSCode and open the platformio.ini file - keep it open while running the commands below.

In the terminal, run the following commands one time to:

• remove the configured OpenOCD package as it will collide with the custom one we'll install
  • if this package hasn't been downloaded yet, run either pio pkg update (update project packages) or pio run (builds the project, and it will resolve dependencies)
• create a PlatformIO symbolic link to our custom OpenOCD package for this dependency (update your user name)

rm -rf ~/.platformio/packages/tool-openocd-raspberrypi 
pio pkg install --tool "tool-openocd-raspberrypi=symlink:///home/dan/Code/Tools/openocd-rp2040-earle"

Note you can choose file:// instead of symlink:// prefix and the custom OpenOCD will be copied into PlatformIO packages location instead of linked to your home folder.

One of the side effects of this command is to re-write the platformio.ini file and remove all comments - in VSCode simply press CTRL+Z to undo those changes (this is why we keep the file open in editor).

Replace the debug environment with following (adjust for your home path):

[env:rp2040-dbg]
;;Edit ~\.platformio\platforms\raspberrypi\boards\nanorp2040connect.json for proper amounts of Flash memory (or other board specifics). Nano RP2040 has 16MB flash onboard, per the specs.
;;platform = https://github.com/maxgerhardt/platform-raspberrypi.git
board = nanorp2040connect
monitor_speed = 115200
debug_tool = cmsis-dap
upload_protocol = cmsis-dap
; ignore all warnings - comment this when adding new libraries, or making major code changes
build_flags =
    -w
    -D GIT_COMMIT=\"DBG\"
    -D GIT_COMMIT_SHORT=\"DBG\"
    -D GIT_BRANCH=\"DEV\"
    -D BUILD_TIME=\"NOW\"
; See Readme - custom OpenOCD with Nano RP2040 Connect Atmel 16MB flash chip specifications added - built from source at https://github.com/raspberrypi/openocd.git branch rp2040-v0.12.0
platform_packages =
    tool-openocd-raspberrypi=symlink:///home/dan/Code/Tools/openocd-rp2040-earle
;;FOR PIO HOME INSPECTION only: to succeed building debug flavor, in efx_setup.h add #define FASTLED_ALLOW_INTERRUPTS 0 before including the PaletteFactory.h; see https://github.com/FastLED/FastLED/issues/1481
build_type = debug
debug_build_flags = -Og -ggdb -DFASTLED_ALLOW_INTERRUPTS=0
debug_speed = 5000
;;debug_svd_path=/home/dan/.platformio/packages/framework-arduino-mbed/svd/rp2040.svd

Debug Session

VSCode is assumed to be the IDE with the codebase open.

• ensure the env:rp2040-dbg (arduino-lightfx shows up in the status bar for the profile (click on it and change it, if it lists something different - like rp2040-rel)
• switch to Debug view
• run the PIO Debug action. For reference, while the launch.json is updated automatically by PlatformIO plugin, the content below is an example of how configuration should look like:

        {
            "type": "platformio-debug",
            "request": "launch",
            "name": "PIO Debug",
            "executable": "/home/dan/Code/Arduino/repos/arduino-lightfx/.pio/build/rp2040-dbg/firmware.elf",
            "projectEnvName": "rp2040-dbg",
            "toolchainBinDir": "/home/dan/.platformio/packages/toolchain-gccarmnoneeabi@1.90201.191206/bin",
            "internalConsoleOptions": "openOnSessionStart",
            "svdPath": "/home/dan/.platformio/platforms/raspberrypi/misc/svd/rp2040.svd",
            "preLaunchTask": {
                "type": "PlatformIO",
                "task": "Pre-Debug (rp2040-dbg)"
            }
        },

• Note that upon finishing setting up the environment, the VSCode will show an error pop-up in the Debug Console tab that states it cannot parse the SVD file. The error is known and talked about in the community (message is rather cryptic) and at this time we don't have a fix (suspect the PlatformIO parser as root cause - note other SVD files are loaded properly). The effect is that Peripherals panel in the debugger is not populated, CPU registries have generic names, etc. but it won't prevent the breakpoints, stepping through the code or variable inspection.
• The execution should stop somewhere in a main.cpp file and from there you can setup breakpoints in your own code