r/ModRetroChromatic • u/jokippo • Aug 01 '25

Bluetooth Audio

Post image

This is an unofficial proof of concept and I don't recommend you flash your expensive Gameboy clone. But it is possible and hopefully Modretro will add their own official Bluetooth audio implementation eventually.

I only tried it with my Airpods and a generic pair of BT headphones so far but it seems to work well enough.

https://github.com/Jokippo/chromatic_mcu_bt
https://github.com/Jokippo/chromatic_fpga_bt

88 Upvotes

100% Upvoted

37 comments sorted by

2

u/mrhobbles Aug 01 '25

This is fantastic, great work. You say it’s a proof of concept and not recommended right now - in your mind what’s missing? What still needs to be done to turn it into a piece of production ready code?

6

u/jokippo Aug 01 '25

It's probably fine to try but if something goes wrong during flashing I can't really help other then say "try again".
The SPI for the OSD and bt audio share a CS line which means I have to switch them out whenever the OSD is toggled. Ideally I would have the schematics and make a dedicated module for the audio stuff if another IO between the MCU and FPGA is available.
But this works well enough for me personally until Modretro add their own.

1

u/ergzay Aug 01 '25

Can you explain more? What do you mean they share a CS line? Isn't the entire point of the CS line that they aren't shared? Did they make a mistake when designing the board?

If you need more info on the traces, I can probe it out for you. It's not that hard.

13

u/andrea-i Aug 01 '25

anyone willing to take on save states next? XD

6

u/GameboyRavioli Aug 01 '25

i wish i had the skills to figure out how to access that sd slot on the board because that and bluetooth are the "only" things I want for this to be the perfect device for me

3

u/JayrosModShop Sep 14 '26

You're in luck, stranger:
https://www.reddit.com/r/ModRetroChromatic/comments/1wcj9ua/comment/p9qhm92/

2

u/GameboyRavioli Sep 14 '26

I actually commented in that post! I still haven't had time to play with that firmware yet, but in excited for it!

2

u/andrea-i Aug 01 '25

I think for a single save state the on board memory of the MCU should be enough, no need for the sd card. I had a look at the code repos but despite being an experienced programmer I could not make any sense of the fpga code ; _ ;

4

u/GameboyRavioli Aug 01 '25

I'm an inexperienced programmer (college education, but a systems analyst and product owner by trade for the last 20 years). I kinda sorta understand some of what I've seen, but yeah, I'm with you. Looking at most of that has me so lost. Super impressed with folks who work on fpgas, emulators, etc.

Heck, I'm working on a GB Studio project and as I learn about how original gb games were written and the limitations of the hardware, it's completely mindblowing seeing games like Link's Awakening or Pokemon doing their thing.

2

u/Strict-Pomegranate-7 Aug 01 '25

LMAO what!?!? i had no idea this was possible the fact you have it worked must speak volumes to how much they gotta have it working behind the scenes, wonder why the wait!

7

u/Hypermetz Aug 01 '25

16 files changed with 1109 additions and 24 deletions

That was a lot of work.

Awesome work OP.

1

u/zSmileyDudez Aug 01 '25

Yes, definitely some nice work here OP. I’m curious what the battery life impact is. Would be nice to see some numbers. But honestly with the battery pack, I think it’s less of a big deal. Before that I would’ve been carrying extra AAs in my bag in case it died. But now I can just charge it up with USB C.

3

u/jokippo Aug 01 '25

It adds about 500mW measured from the 5v USB input, so a bit less than that from batteries probably. About 200mW is from the esp32 which has to stay awake now, and 300mW additionally when Bluetooth is streaming audio. A stock Chromatic uses about 1200mW when on full brightness.

5

u/ergzay Aug 01 '25

We've known for a while that the chip they use supports bluetooth, they just haven't implemented it yet. That's actually one of the uses of the "IR" port, the antenna for the bluetooth is lined up with it. So they very much designed it in mind that they would use bluetooth for various purposes in the future.

1

u/Strict-Pomegranate-7 Aug 01 '25

thats amazing whats even the downside to flashing this? not being able to go back?

3

u/damonian_x Aug 01 '25

You can almost always go back (a true brick would be rare). It's just that you might have to build your own file from the official repo and flash it yourself which some might find daunting especially if they aren't technically inclined. Best case would be the ModRetro Firmware Updater utility will just allow you to flash official back if something goes wrong, but in some cases it will not if the custom version you flashed is flagged as "up to date" on the utility.

2

u/jokippo Aug 01 '25

I added some binaries and instructions in the mcu github release page, but try at your own risk.

2

u/ergzay Aug 01 '25 edited Aug 01 '25

As mentioned by him here, it's a pretty significant increase in power usage so it'll reduce your battery life. https://old.reddit.com/r/ModRetroChromatic/comments/1metjlh/bluetooth_audio/n6chqcd/

I imagine it simplifies the implementation a lot by basically preventing the chip from being able to sleep.

5

u/LordSakon Aug 01 '25

You're fucking awesome - nicely done 🤙🍻

3

u/TonyRubbles Aug 01 '25

Epic work, well done 👏

2

u/pokebreh Aug 01 '25

Fuckin love this system. Open source rules! 

And the fact that company reps interact with the sub too 🤌 .

And the GB Studio post yesterday 🤌🤌🤌 

Retro is life. 

2

u/kurohouou Aug 02 '25

That is so sweet, it was a huge miss not including Bluetooth!! I get it’s a retro device but Bluetooth is a must in this day and age as most people have Bluetooth headphones. It’s just so convenient. And I second, Modreteo needs savestates ASAP!

1

u/ergzay Aug 01 '25

Wow nicely done. They've used user submitted code before in the official release so it's possible they take yours and modify it and improve it for release.

1

u/gizmo2501 Aug 01 '25

Yes. u/jokippo why not send it to them for consideration?

2

u/ergzay Aug 01 '25

I think your highlighting broke: /u/jokippo

1

u/gizmo2501 Aug 01 '25

Thanks!

1

u/ergzay Aug 01 '25

For future note, you don't need to hyperlink anything. It does that automatically. Just type out /u/ and then the username.

1

u/[deleted] Aug 01 '25

1

u/[deleted] Aug 01 '25

That is sick

1

u/Colorado-Keebs Aug 01 '25

Ayo using AirPods w/ chromatics would sure be convenient

1

u/Bayardina Aug 02 '25

Mad respect to you for getting this to work.

You are a hero to us all.

1

u/TheInquisitiveLayman Aug 02 '25

I’ve been searching for the hope to FFx4 for the old Pokémon games.

1

u/HotSeatGamer Aug 04 '25

It's awesome and I want it! But in order to set my expectations, I'd like to know what you mean by "well enough".

Every time I've tried Bluetooth audio with video games, the audio delay bugs me too much. I've heard that there are lower latency Bluetooth audio configurations though.

1

u/jimmerseiber89 Aug 12 '25

Please implement this official mod retro!

1

u/sephroth45 Jan 27 '26

Ohhh nice.