Murmur

Murmur is a small audio media player...something light and easy to take with you for a walk, a workout, or a luch break, that "just works" without any Bluetooth hastles and without any internet distractions or UI annoyances. And something kids can take to bed to listen to music or audiobooks without worrying about the internet invading their privacy. 

Known Issues

Murmur v 1.0 is functional. However, there are some issues that should be addressed in a revision. In decreasing order of severity these are:

• The digital audio converter (TAD5242) can lock up during low power states or during assembly, requiring a power cycle. However, at the moment, the only way to cycle power is to disconnect the battery, which requires opening the Murmur enclosure. In revision 2, power to the DAC will be controlled via a GPIO pin on the ESP32 via a transistor, enabling the firmware to ensure proper startup sequence on the TAD5242.
• The 5 way nav button turns out to be very difficult to 3D print an acuator/cap for and is fragile, easily breaking during installation. Version 2 will replace this with 5 independent touch buttons.
• There is no battery level indication possible. Addition of a "fuel gauge" chip, or even simple voltage divider and measurement on an ADC pin on ESP32 would allow letting the user know where the battery level is at.
• A larger display would allow for a more informative user experience.

Design Overview

ESP32-S3-WROOM module reads audio from microSD, converts to I2S stream and sends to TI TAD5242 DAC/Headphone driver. Powered by lithium ion battery. Charge (and program firmware) via USB-C. Playback over wired headphones/ear buds via 3.5mm stereo audio jack. 

Additional Components

In addition to the assembled PCB, the following components are required. Some links to Amazon and Aliexpress are given below. These are not affiliate links and are given just as examples of possible sources. 

1. Hookup wire. I like 30 gauge as it is flexible and does not take too much room.
2. LiPo battery. A thin one is needed, either the 303450 (3mm thick) or 383450 (3.8mm thick) form factor. 
3. M2 inserts. M2x2 are needed for the low profile display mount. Longer ones can be used for securingn main PCB and case back. 
4. A microSD card to load your music or audio on to.
5. Headphones or earbuds to listen to your music

Assembly

1. Carefully break the minijack subboard off from the rest of the board along the "rat bite" holes. Snap or cut off the "arms" extending from the main PCB towards the display. These were utilized during PCB manufacture but are needed for assembly and will get in the way of the screw mounts at the end of the enclosure.
2. Connect the 4 pads between the minijack board and the main board by soldering short wires between them. I like to use 30 gauge wire to reduce interferance with enclosure shutting.Wires should be soldered to back of both boards (See photo below).
3. Connect the 4 pads between the display board and the PCB using wires of sufficient length to allow placement, including some extra so the wires can be tucked around the battery in subsequent step. Note the square "Ground" pad on both display board and PCB. Wires go in order from there. Wires should be soldered from the back (see photo below). 
4. Solder the + and - wires from LiPo battery to back of board.
5. After printing enclosure, press M2 inserts into the 11 holes. For the display mount, M2x2mm inserts must be used due to low clearance. Longer inserts may be used in the other holes.
6. Secure PCB and display with M2 pancake screws, sometimes called SSD or Hard Drive screws. Here is one example. 

Here is a photo of the assembled player. 

Finally, secure bottom of case using 5 M2 flat head screws.

Firmware

Firmware can be flashed over USB using the ArduinoIDE as follows

1. Install the [Arduino IDE](https://www.arduino.cc/en/software) with ESP32-S3 board support.
2. Install the required libraries: **Arduino AudioTools**, **Adafruit SSD1306**, **Adafruit LIS3DH**.
3. Open `firmware/murmur/murmur.ino` from the repo.
4. Select the **ESP32S3 Dev Module** board and configure: 8 MB flash, USB CDC on boot enabled.
5. Click Upload.

Loading Music and Audio Files

Load whatever MP3's you would like onto a microSD card. You can include folders on the microSD card which will be treated as "Playlists". Folders nested in other folders are not supported. 

Using the Player

For full instructions on how to operate the player, see the User's Manual.

Project Status

PCB design complete. Enclosure design complete. 

This version is functional. Known issues as noted above. Revision to v2.0 in progress.

Latest updates can be obtained by opening the project editor below and from:

https://github.com/ejkreboot/murmur