Last summer, @Wesk and I were theorycrafting a Wii reg board for undervolting that would solder directly to the motherboard. Such a board would remove all voltage droop from wires and might allow for more extreme undervolting, while also being more compact than any other voltage regulation scheme to date! I did some crappy mockups at the time using MUN3CAD03s and determined there was more than enough room to fit everything. The project got put aside after that as I was developing the LOLWUT trim.
This March, @loopj's awesome Wii Power Strip and wundervolt inspired me to revisit this idea! I decided to prioritize the following things in the design:
- High efficiency regulators, especially for the 1V and 1.15V rails
- Buck-boost for 3.3V
- Fits within the outline of a conservative OMEGA trim as seen above
- I2C-controlled undervolting with a companion homebrew app
- ATtiny1616 for compatibility/feature parity with wundervolt
- Some sort of hardware-based "safe mode"
VBAT (well, really VSYS) and GND solder directly to the board. Thundervolt will not have charging onboard because (1) there isn't room without sacrificing reg efficiency and (2) charging generates a lot of heat that I don't want to dump into the tiny mobo.
It'll rely on an external charger board to switch VBAT/VSYS on and off with a PFET. The board is VIPPO (via-in-pad plated over) because that makes the routing more fun/interesting, and I wanted an excuse to use VIPPO.
The regulators I'm using are all I2C-controllable, but they are configured to come up at the nominal Wii voltages without I2C configuration.
- x2 TPS628681ARQYR for 1V, 1.15V
- x1 TPS628682ARQYR for 1.8V
- x1 TPS63810YFFR for 3.3V
The MCU is an ATtiny1616— the same one as wundervolt. loopj and I think we can make wundervolt and Thundervolt compatible with the same undervolt configuration homebrew app.
I originally had an NTC thermistor onboard, but I eventually replaced it with a TMP1075 I2C temp sensor. I also added some hand-drawn lightning art to the PCB!
Keep in mind the vias will be plated over, so they'll be invisible and all the pads will be smooth. The Swiss cheese preview is due to KiCAD limitations.
There's also a status LED, a safe mode jumper to force the onboard regs to come up at default voltages, and a U10 emulation pin which doubles as a Wii reset control output. Basically, Thundervolt should be able to hold the Wii in reset while it configures the regulators, and then let it boot after the regs have settled at their reduced voltages. We'll see if that works as expected.
In my opinion, this is the endgame for Wii portablizing. A custom motherboard could never compete with this level of integration since Thundervolt stacks directly on top of the mobo. Paired with nandFlex, loopj's periphlex, and AVEflex or fujiflex, the OMEGA trim can be made fully modular with minimal soldering and probably 1% of the work a custom mobo like Vegas requires.
Anyway... now I just need to design a jig PCB that surrounds the Thundervolt board, so I can use a solder paste stencil on it. After that will be ordering, assembly + testing, and a fully OSHW release on GitHub.
Last edited:
