Overview

Physical controls for a more enjoyable media playback experience.

Features

• Responsive volume knob & mute button.
• Transport controls (play/pause, stop, FF/REW, skip tracks).
• Pair up with your favourite Bluetooth® speakers.
• Quick, physical connection (don't have to go through menu system to pair with keypad & speakers).
• Customizable controls/scheme.
• Customizable setup: Optionally connect USB hub/dock for added features, for example:
  • mirror phone to TV w/HDMI out: Watch videos on a bigger screen
  • add keyboard: Better typing experience for texts/emails.
• Solderless project.

Main hardware

Program your device

To get your RP2040 macropad to act as a media controller, it needs to:

1. detect keypresses and changes in the knob position
2. send out corresponding keyboard messages to the attached USB host device (ex: a phone).

My own implementation for this "media hub" is written for Adafruit's CircuitPython, and can be found here:

• 💾 MediaController project README (see MediaHub_AFMacropad). 🚀 Installation instructions.

Overview

The MyState library delivers a framework to simplify configuration and control of appliance-like devices. MyState makes it quick-and-easy to define device state that is readily controllable from the outside world.

Writing code to control state and react to sensor inputs is time consuming. Why not (mostly) solve the problem once, and re-use that infrastructure to build up your next project faster?

Features

• Route raw sensed input signals through custom signal-generating filters, and provide a solid, uniform user-interface experience.
• Load custom device configuration/controlled state on startup by calling ListenerRoot.script_load().
  • A good way to "recall presets" at the press of a button when manual configuration is a bit of a pain.
• Let anyone control your device using SigLink interface (by means of a serial/other IO connection).
  • Ex: Let a PC control your device using MyState "signals" sent across the USB/serial connection.
  • Configure your device using a custom-built GUI or web interface.
• Applies more formalized (hopefully readable) patterns of "filtering" input/sense signals, and applying a "reactive paradigm" to respond accordingly.
• Aspires to enable a future of composable, modular devices where extension/customization is the norm. Getting our products to cooperate should not be a constant battle requiring mounds of ugly hacks.

✨Highlights

• Call SigLink.process_signals() to enable quick-and-easy device control via serial/IO connection.

Details

The framework provides access to device state using something the author calls a "Model-React-Controller" (MRC) -- analogous to a Model-View-Controller.

Code Repository

• Development repository on github: MyState.
• Project examples (self contained): HomeLights_Wired. --- Download:v0.1.

SampleProj: HomeLights_Wired

Overview

Physical controls for a more enjoyable media playback experience.

Features

• Responsive volume knob & mute button.
• Transport controls (play/pause, stop, FF/REW, skip tracks).
• Pair up with your favourite Bluetooth® speakers.
• Quick, physical connection (don't have to go through menu system to pair with keypad & speakers).
• Customizable controls/scheme.

This project tries to improve over the original "Media hub" presented here.

• More compact design
• Bigger volume knob - not interfering with macropad keys.

🛒️List of main material/hardware

(See section "More tools/materials/hardware" near the end of this note for extras)

Overview

This page gives an overview of microcontroller form factors typically used by the maker community (at a beginner/intermediate-level). The intention is to assist in finding the right fit for your projects. To achieve this, a high-level introduction of said form factors, and simple feature/property matrices will be presented. Naturally, coverage will be limited by the author's personal knowledge of available options (even if popular in other circles).

The focus is primarily on Adafruit products (tends be available in these popular form factors), but also makes associations to names used by other companies (aliases).

Common form factors (FF)

The following sections present common form factors in decreasing order of size. A few different feature/property matrices will follow (Sorry. Not sure how to link to a lower section).

FF: Mega/Grand Central

Alias: Uno (Arduino), Metro (Adafruit)

A key development board instrumental in popularizing the entire microcontroller-based DIY/maker movement. The UNO significantly reduced the barrier to entry for microcontroller-based prototyping & development.

Note that there are currently 4 revisions of the UNO format (Currently at UNO R4). Arduino describes the differences over time in this article. Another article describing the differences in more detail is linked here (Not verified by the author, but information looks reasonable).

Other useful information:

• Considered relatively large by Today's standards (though realistically still very tiny at ~2.1x2.7").
• Popularized the idea of stacking "shields" on top of the base microcontroller board.
• ...but newer form factors have become so small, that the trend is to stack add-on boards (like FeatherWings) side-by-side using "doubler", "tripler", and "quadrupler" carrier boards.

FF: Feather

Overview

This note presents a few different ways of building an microcontroller-based IR receiver. It is meant as a complement to the "PC media remote" note.

The idea is to somewhat parallel "Software design patterns" -- only for physical hardware builds. The note provides a variety of implementation examples for an IR receiver project. Juxtaposition is used to compare various different mechanical/mounting systems that provide structure, and also different practical connectivity solutions. Hopefully these options will make builds feel a bit more approachable, and possibly inspire new ideas.

Regarding the overall design philosophy: Attempts were made not to solder everything together in one monolithic block. Design often involves making mistakes, so having a way to easily re-configure your solution as it develops really helps.  More specifically, I find that building "blocks" in a somewhat modular/generic fashion is preferable to building something that is completely "application-specific".  As a bonus, if your blocks don't quite work out the way you want, they can more likely be re-purposed in later projects.

A good way to improve on the original "PC media remote" breadboard example is to use the IR receiver module (#5939). The build pictured above makes use of the STEMMA-QT port from a PiCowbell protoboard, and mounts all components to a 5x5 Adafruit swirly grid. Overall, this build should be a little more robust than what can be obtained with the breadboard solution, yet still be achievable without any soldering (if using Pico board with pre-soldered headers).

Some things to keep in mind:

• Need a custom 4-pin JST-SH to 3-pin JST-PH cable.
• Make sure the pin order is correct to avoid damaging the circuits (especially power/gnd).

Connecting the 2 boards in this fashion requires modifying a pre-built JST-SH cable (this one, for example). Crimping JST-SH connectors can be a bit difficult due to the small size, but removing the 4th (yellow) wire from a 4-pin connector is a bit more manageable. A hobby knife can be used to ⚠️carefully lift the plastic tab to release the pin/wire. Once that's done, JST-PH pins can be crimped to the other end of the cable, which in turn snap into the 3-pin JST-PH connector needed for the IR receiver terminal.

Program your device

Installing CircuitPython environment

1. Download .uf2 file here:
   • https://circuitpython.org/board/raspberry_pi_pico/
2. Plug in USB cable from PC to RP2040 board while holding the BOOTSEL button.
   • A new drive should get mounted on your system.
3. Drag/drop downloaded .uf2 file onto newly mounted drive (RPI-RP2).

Installing libraries and project code

From "CircuitPython Library Bundle" (download here):

1. Copy from bundle .zip file to the microcontroller [drive:]\lib\ folder:
   • adafruit_hid

From the PCMediaRemote release page (download here):

1. Download and unzip the "Source code (zip)" file from the "Assets" section.
2. Copy the "unzipped" custom project code to microcontroller [drive:]:
   • [PCMediaRemote folder]\lib_cktpy\* => [drive:]\lib\
   • [PCMediaRemote folder]\pkg_install\MediaRemote_RP2040\*.py => [drive:]\

NOTE: Feel free to check for newer versions of PCMediaRemote on the releases page. Code from the main branch might also be functional, but explicit releases are less likely to have issues.

Customizing your solution

You can directly modify the main.py file on the [drive:]\ folder. Every time you save the file, CircuitPython will restart with the updates applied.

Note that if the file gets corrupted for some reason, your changes will be lost. It is recommended to work from a folder on your PC, and manually upload (ex: drag/drop) the changes to the CircuitPython drive.

Overview

A media remote receiver for your PC/MAC/thing supporting keyboard media keys.

• Also works with many smart TVs and phones.
• Flexible CircuitPython-based solution can easily be adapted to other microcontrollers/IR remotes.
• Built-in IR signal decoder utility on serial monitor output.
• An easy, inexpensive, solderless build! (if desired)

Wired solutions: DC adapters & USB PD

High-power: DC adapters

Regulators built into most microcontroller development boards typically cannot supply much current. A common solution is to use an DC power adapter (barrel/terminal blocks):

• Wall supplies (CAT#137)
• DC adapters (CAT#557)

Some interesting options to take note of:

Regulators tend to come in 3 flavours:

• Linear regulators: Fed from a higher voltage. Typically less efficient than their "switching regulator" counterparts. Typically powered by another (higher voltage) regulator such as a DC power adapter.
• Step-down ("buck"): A switching (voltage) regulator fed from a higher voltage. Typically powered by another (higher voltage) regulator such as a DC power adapter, but can also be driven by a battery.
• Step-up ("boost"): A switching (voltage) regulator fed from a lower voltage. A useful tool to generate higher voltages on devices that aren't normally expected to need them. Commonly used in battery-driven applications where you cannot (don't want?) rely on batteries to generate the high voltages needed.

🧠️Smart load sharing

Some solutions include "smart load sharing". As with everything, not all "load sharing" is created equal, but will tend to implement the following current/power management features:

• Simultaneously power your project while charging.
• Redirect excess current to charge battery when plugged in.
• Avoid unnecessary battery charge/discharge cycles +extending battery life.
• Can be used without a battery being connected.
• Live disconnection of battery or main power source *without losing power.
  • *Check product specs to make sure this is actually supported.
  • Otherwise: glitches could result in unreliable power or unsafe conditions (damage circuits).

Watch this Adafruit product video (1000C) for further explanation.

Portable solutions: batteries & solar

At the time of writing, there are 4 popular solutions to power portable projects:

• Non-charging: converting battery voltages up ("boost") or down ("buck") to something better suited for your project.
• "Just charger": Separate battery chargers. Won't directly power the project, but used to complement "non-charging" solution.
• USB-fed battery chargers: Not only can your project be powered by a battery, but some options allow that battery to get charged up automatically when connected through a USB port. This is what happens inside most cell modern phones.
• Solar-capable battery chargers: For even more autonomy, some options allow the connection of solar cells. Many solar capable solutions also allow for safe USB battery charging even when connected to a solar cell. Note that not all solar-capable chargers allow safe charging on USB, and so choosing the right might require some additional investigation.