High Capacity Raspberry PI MP3 player

Question

I've had this idea rambling around for a while and I felt it's necessary to share it with the outside world, I've never been fond of only a handful of computers controlling the MP3 production market and forcing users to live within outdated standards. It's 2am at the moment so if I loose you anywhere just let me know. Would if be even possible to take a RPI Zero attached to a simple E-Ink display and a few buttons for I/O and have it mount and read 2 (TWO) 128gig micro-SD cards? That will give a user 256 gigs of pure musical enjoyment. How would someone go about developing software and hardware that can read and sync together two MIcro-SD cards into a single one and play all the content off of it?

royleith · Answer

I have two Zero cards which make it possible.

The first is a Referencedesign card which fits underneath the Zero and adds a three (full-size) USB port hub and WiFi by picking up the gold pads of the Zero's microUSB port (which cannot be used as it is the port driving the hub).

There are tiny microSD card readers that plug into a standard USB port (beware, some are limited to 32GB. Mine was, but only cost £1!). That can add the first 128 GB, but you might as well get a 256GB microSD card and reader.

Or, you could use a usb SSD (a pricey option, but good for capacity and low power).

The second card is a Pimoroni pHat DAC with 3.5mm and phono jack audio outputs (the Zero has no built-in sound).

My Raspi 3 B has a 64GB microSD boot card with a third partition for Ogg Vorbis audio files of all my music (it's only just large enough. I may go 128GB, next). The Zero's boot microSD can provide the second 128GB. Please note that the boot partition must be first and the rest of the file system in the last partition. The 'third' music partition needs to be between the two system partitions. Again, a 256 GB card would be sensible, but I don't know whether the Raspi supports this capacity.

The advantage is compactness. The disadvantage with a music partition on the boot microUSB card is that it is not easy to preserve the music partition when a new OS is installed.

The Zero has no video connector and so the screen would, probably, have to use the HDMI interface. It might be possible to use the same Raspberry Pi I2S pin as the pHat DAC, but that would require the ability to set the software and hardware addresses. Since the E-Ink display does not need continuous signals, it might be possible to drive it via bit-banging on a GPIO pin, but this might be a coding challenge.

Arrangements would have to be made to wire out the unused GPIO pins that are covered by the pHat DAC connector. Those pins can provide push-button controls. You could implement cursor buttons, but a rotary encoder would be more fun.

Command line audio player software can be controlled by Python with TKinter to provide the on-screen display. I have done something similar to provide a mixer for the Cirrus audio card.

To make it portable, a ZeroLiPo shim could be used together with a suitable LiPo battery. On the other hand, a mobile phone re-charger might be just as compact and much easier to recharge (just plug it into a Zero USB port when the Zero is on mains power).