Media Player Card
In the Merveilles community, the question of how to listen to music in a sustainable non-steaming fashion comes up every now and again. People in the community will share different methods, and usually we agree that the tiny Sanwu Audio Player as shown in the XXIIVV wiki is a slick and tidy solution.
Recently I bumped into a very similar board on AliExpress for less than $2. It's sold by "Tenstar Store" and titled "Bluetooth Audio Receiver board with USB TF card Slot decoding playback preamp output A7-004 5V 2.1 Wireless Stereo Music Module"
So I got a few of them with the intention of mailing out extras to anyone in the community who's interested. I got a few takers, however before sending them out I agreed to try some modifications. By the way, if you're curious about what a "TF Card" is - it's the same as an SD card, apparently just an alternate name.
The board can be powered by micro USB quite easily, but if you want to make it portable, you'd have to use a micro USB portable power bank. I thought it might be nicer to enable a slimline rechargeable LiPoly battery instead. The first problem is that the LiPoly batteries I can get from Adafruit output 3.7 Volts, but the player requires 5 Volts. I tested this out and while it will power on, it can only provide radio when underpowered and completely skips music playing mode. So I got a MiniBoost board. This tiny board can transform the LiPoly's power output up to 5 Volts, at the cost of some milliamps. I wired it up to test, and indeed it works. With the MiniBoost board wired in-between the LiPoly battery and the media player, I'm able to listen to music stored on the SD card.
Next I'm testing a Micro Lipo USB-C charging board. This board, plus the MiniBoost and one of the small LiPoly batteries all fit within the footprint of the media player. I'm hoping to verify that I can wire these things all together so that the LiPoly battery can be recharged without disassembly. To keep all these pieces together, I've designed a metal plate to match the board. Once those are received I'll assemble the players with enhancements and send them out (minus the battery).
The charging board works. The wiring is quite simple: Battery into charging board. Charging board has "Batt" and GND out which goes to VIN and GND on Booster, VOUT and GND go to the media player. This allows the battery to be charged, and when not charging, to provide power boosted to 5V to the media player. The last step is to finalize how to keep the wiring as minimal as I can so that the back plate (once they arrive) can enclose these additional elements nicely as a unified package.
The back plates arrived, and thankfully the sizing and holes line up. Now it's there are two small steps left: implement tighter wiring and find the right combo of spacers and washers to account for the height differences between the holes and power/charge boards.