Thundervolt

[YveltalGriffin]

Thundervolt is a stylish, highly integrated power hat for Nintendo Wii, with software-controlled undervolting. It is fully open source and permissively licensed on GitHub!

There are three Thundervolt board variants. For details on the differences between each version, see the hardware folder on GitHub. As of 2024-07-07, both Thundervolt 1 and Thundervolt Lite have been released.

Features

• 0.8mm 4L VIPPO rigid PCB — solders directly to 4-layer Wii motherboards
• 55 x 47mm — fits within all but the most extreme trim outlines
• 2.4V to 5.5V input (intended for 1S li-ion or 5V USB-C)
• Highly efficient I2C-controlled buck regulators for 1V, 1.15V, and 1.8V (η > 90%)
• Highly efficient I2C-controlled buck-boost regulator for 3.3V (η > 90%)
• Dynamic undervolting, configurable via Wii homebrew app
• Safe mode solder jumper to force stock voltages
• Wii power-on reset functionality (aka U10 emulation)
• Onboard TMP1075N for temperature monitoring and emergency overtemp shutdown
• Integrated INA700s for realtime voltage/current/power monitoring (Thundervolt 2 only)

The GitHub repo has details about how to order the boards, compile the homebrew, flash the firmware, etc. Loopj and I will try to write up some nicer docs eventually-- probably around the same time Thundervolt Lite is released.

Here's a quick YouTube video demonstrating the core features of Thundervolt:



And here's a recording of the homebrew app running on Dolphin in 4K, to showcase the graphics, music, and sound effects:



Next Steps

• 2024-07-07: Thundervolt Lite tested and released on GitHub.
• 2024-07-14: Assembly guidelines up on GitHub.
• Thundervolt 2 is much more complex and it may be a while before loopj and I are ready to release it.
• Mjolnir, a companion BMS board to handle charging and fuel gauging, is in development. Mjolnir will integrate tightly with the existing Thundervolt app.
• The homebrew app will get built-in stress tests at some point. We want to have dedicated CPU, GPU, MEM1, and MEM2 stress tests to make it easier to validate undervolt stability without exiting the app.

Credits

• @YveltalGriffin designed the Thundervolt hardware and wrote the homebrew app
• @loopj wrote the Thundervolt firmware, I2C drivers, and contributed a great deal to the homebrew app
• Alex (@supertazon) contributed the GRRLIB rain effect and other graphics used in the homebrew app
• @ShockSlayer composed the homebrew app's background music

This project has truly been a community effort! Huge thanks to my collaborators for all their help in bringing Thundervolt to life. I can't wait to see it used in some awesome projects!

 

[loopj]

MFW I can finally undervolt Wii Sports

 

[ShockSlayer]

Happy to have been able to contribute.

 

[thedrew]

This is it. End game for undervolting. Yall are amazing. How are the temps of the regs during testing being that they are right next to the CPU/GPU? I'm thinking of using some thick thermal pad to attach the regs to the heatsink or something just in case.

 

[YveltalGriffin]

All of the regulators are rated up to 125°C! While the regs don't have die temp sensing, the Thundervolt TMP never even reached 50°C in my tests. So, there's no need for additional regulator cooling.

 

[Teatimetim]

Is there a control in place to prevent you from undervolting too far and not being able to boot the wii back up?

 

[YveltalGriffin]

Yep, there's a safe mode solder jumper on the Thundervolt PCB. Bridging the jumper (or connecting & pressing a button as shown in the demo video) forces stock voltages. You can then edit your persisted undervolt settings to get things stable again.

The app also enforces hard limits on all the voltage rails, so you can't irreparably damage your Wii by going too high or too low. The upper limits are the stock voltages, and the lower limits are 750mV, 850mV, 1300mV, and 3000mV.

 

[Shank]

Can we undervolt the ground line to save even more power? Asking for a friend.

 

[Customledmods]

This is amazing! Thanks for sharing with the community.

 

[Stitches]

The future is now!

 

[YveltalGriffin]

Thundervolt Lite has been tested and released on GitHub!

Thundervolt Lite is way cheaper than the other variants, only costing $7 for 10 bare boards, while being functionally identical to Thundervolt 1. Please see the hardware folder on GitHub for KiCAD source files, Gerbers, BOM, and details on ordering.

The Thundervolt app already has support for Thundervolt Lite built in, so there's no need to download a new build.

Detailed assembly guidelines with step-by-step photos will be added to the GitHub repo later this week. My hope is that this cheaper version will make Thundervolt more accessible to folks!

FYI: I will be selling my leftover Thundervolt 1 and Lite PCBs at cost. Be on the lookout for a For Sale thread.

 

[thedrew]

Just when I thought it couldn't get any better!

 

[YveltalGriffin]

Detailed assembly instructions have been added to the Thundervolt repo! See ASSEMBLY.md in the hardware folder.

The docs show how to use the jig PCBs, which make solderpaste stenciling a breeze. There are also some equipment recommendations, as well as notes on rework, bring-up, and flashing the firmware.

I also listed my leftover Thundervolt PCBs for sale here.

 

[YveltalGriffin]

I have an update regarding a minor "bug" @loopj and I have noticed with Thundervolt. The risk to end users is low, but just to be extra safe, I have released new board revs and firmware to address the issue.

~

During Thundervolt testing, I noticed some strange behavior with the U10 emulation. In certain scenarios, especially when measuring or probing U10 while the mobo is on, latchup of some kind occurs on the Wii's U10 pin, and Thundervolt's faux open drain U10 emulation will fail.

When this happens, the U10 pin will be "stuck" at 3.3V, and will backfeed into the ATtiny, which is running at 1.8V. With Thundervolt connected, the U10 pin will measure somewhere in between the two voltages, usually ~2.2V or so.

This sometimes results in a Wii that can't be reliably reset at power-on, leading to all the classic U10 symptoms: no video, very slow boot times, Bluetooth not working, etc.

Note: I say "sometimes" because so far, only I have observed real issues stemming from this. Loopj has seen the ~2.2V U10 phenomenon, but it has not impacted his test mobo's functionality. It seems sort of mobo-dependent, which is why risk to end users is low.

BitBuilt veterans may recognize the "stuck U10" issue I'm describing-- it happens sometimes with traditional U10 relocations, too. We don't know why it happens on stock consoles, and likewise, it's unclear why it happens with Thundervolt. It might be from ESD damage, or some interaction with the ATtiny's faux open drain output.

~

Assuming the issue IS related to the ATtiny faux open drain output, the solution is pretty simple: isolate the ATtiny from the U10 pin with an N-channel MOSFET. This makes the U10 emulation a true open-drain output, and electrically identical to the original IC.

Thundervolt Lite now has a SOT-523 NFET, and Thundervolt 1 has a chipscale DFN1006-3 NFET.

To maintain firmware compatibility, the new Thundervolt boards have a previously-floating GPIO tied to GND. The ATtiny firmware will check this pin to see if a FET is present and drive the U10 output accordingly.

The hardware and software changes are very minimal, but they are still untested. I will try to validate everything ASAP.

TL;DR:

• There is some unexplained Wii U10 behavior that sometimes results in boot issues with Thundervolt. (It can happen with normal U10 relocations, too!)
• New TV board revs with tweaked U10 circuitry have been released. If placing a new order, always order the latest Gerbers and BOM!

Important takeaways:

• Original Thundervolt boards still work fine!
• Avoid probing or measuring the U10 pin while your Wii is on. And exercise proper ESD precautions!
• You probably won't have any U10 issues with original TV boards. If you do, please let me know, and either
  • Do a normal wireless U10 relocation, or
  • Order the latest rev boards