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Custom MP3 Player

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vitt13:

--- Quote from: Zresh on June 15, 2024, 07:42:43 AM ---here are a few changes to the spec's list and a very rough picture of what I'm planning for the body
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It almost reminds me Innioasis Y1 player  :) https://fccid.io/2A6DB-Y1/Internal-Photos/Internal-Photos-6262700
But it's with lower battery capacity, smaller form size than you request and BTW without dedicated hi-res DAC.

amachronic:
For what it's worth I've been working on an STM32H7-based design using external SDRAM, also targeting an iPod 6g-like form factor. These are the specs:

* STM32H743 @ 480 MHz
* 32 MB of SDRAM
* SD card bus up to 25 MB/sec
* USB Type-C connector muxed between USB 2.0 HS PHY (for main USB functionality) and STM32's builtin USB 1.1 PHY (so it can be flashed without SWD)
* 3.5mm headphone jack driven by PCM5102A DAC + LM4810 amplifier
* Support for headset inline remote buttons compliant to the Android 3.5mm accessory specification
* Headset mic support -- not going out of my way for this, so there is a chance it will not work very well or at all. It's just there as a consequence of supporting headset buttons so why not.I've almost finished with the high-speed bus routing: SDRAM is done, USB is mostly done. The SD bus isn't routed but should be very easy to do. Still need to place the LCD, buttons, power supply, crystals, and audio components. I'm planning on a 320x240 LCD over SPI, which is maybe not ideal, but the only other option is a parallel RGB bus and I'd rather not route another big parallel bus since things are already pretty crowded near the MCU. I'm trying to stick to a 4-layer PCB because moving to 6+ layers bumps up the cost for prototypes significantly.

Compared to speachy's wishlist I am missing a few things (UHS-I, OTG, separate line-out port, 60 FPS display) but they aren't showstoppers and could probably be added in a future revision. Only UHS-I is really a pain, because then you need a level shifter + 1.8v supply on the board, and most of my parts require 3.3v.

Right now I am trying to do the case design since I now need to place & route the external connectors. I'm thinking of a Sansa-esque d-pad with 2-4 extra buttons on the faceplate, volume buttons on the side, and a power/hold switch on the top edge; another option is a power button on the top/sides. USB and SD connectors on the bottom edge and 3.5mm jack on the top.

One of my constraints is only using components which are plentiful on LCSC, mostly for cost and convenience, and hopefully the parts will still be available in a few years time. A better option for the MCU would be the STM32H7S3, which has an embedded USB 2.0 PHY, and the PSSI interface which I think could be used for connecting 8-bit parallel 8080 LCDs in conjunction with a separate clock output, but it's not available from LCSC. Proper PMICs are hard to find, as are high quality audio codecs, hence why I've gone for the discrete DAC + amp combo. But barring any stupid mistakes on my part I think the quality should be fine.

I do plan on releasing the PCB and case designs as open-source once I get closer to finalizing them.

7o9:

--- Quote from: amachronic on June 22, 2024, 12:33:35 PM ---I do plan on releasing the PCB and case designs as open-source once I get closer to finalizing them.

--- End quote ---

Sounds very interesting!

Do you plan do some sort of batch of assembled devices too? I would be happy to support that.

lubatur:
I would also like to support this.

speachy:

--- Quote from: amachronic on June 22, 2024, 12:33:35 PM ---For what it's worth I've been working on an STM32H7-based design using external SDRAM, also targeting an iPod 6g-like form factor. These are the specs:

* STM32H743 @ 480 MHz
--- End quote ---

Sweeeeeet.   FWIW I am particularly fond of the STM32 family, and that has only grown the more I've had to deal with the competition....


--- Quote from: amachronic on June 22, 2024, 12:33:35 PM ---I'm planning on a 320x240 LCD over SPI, which is maybe not ideal

--- End quote ---

Given the STM32's DMA engine(s), we could probably just have it on a continual (double-buffered) refresh cycle.  At 320x240x16bpp, 25MHz 1-bit SPI would net us about 20fps.  If we can get 2 or 4-bit SPI that ought to scale nearly linearly.
 

--- Quote from: amachronic on June 22, 2024, 12:33:35 PM ---Compared to speachy's wishlist I am missing a few things (UHS-I, OTG, separate line-out port, 60 FPS display) but they aren't showstoppers and could probably be added in a future revision. Only UHS-I is really a pain, because then you need a level shifter + 1.8v supply on the board, and most of my parts require 3.3v.

--- End quote ---

Yeah, no 1.8v supply does hurt. What do you intend to do for power/battery management?  (And not having UHS-1 won't really be visible except when doing file transfers...)

I look forward to seeing what you come up with!

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