Worklog Thundervolt

YveltalGriffin

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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.
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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"
I dubbed the board "Thundervolt" and whipped up a suitable logo. Then I imported loopj's Power Strip outline into KiCAD and got cracking!

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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.

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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
I managed to fit dual XFL5015 inductors for the 1V and 1.15V rails. These have very low DCR and high Isat and as a result, the core regs should be ~92% efficient which is amazing.

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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!

thundervolt_mobo.PNG


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.

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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. :)
 
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This looks absolutely epic! A compact, Omega-compatible (ish) power supply for portable Wiis that supports undervolting would be hugely helpful, at least for me. Can't wait to see this project reach completion! I'm especially excited for the the predicted low-price mass-manufacturing can provide, and I really hope this gets a LOT more community support in the near future! The open-source nature is just the cherry on top, and I'd love to incorporate this into my project.
 

loopj

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I'm really excited about this board.

Apart from the features Yveltal pointed out, here's what I'm pumped about:
  • Having battery management on a separate board arguably enables more flexibility and modularity:
    • You can use Thundervolt on both Wii micros and portables
    • You can use different battery charger ICs to enable the use of higher voltage batteries (eg. 4.47V)
    • Or, you can stick with the tried and tested battery charger ICs like the BQ25895
  • Even though there is (currently) no connector on this board for power, that doesn't preclude you from having a connector on the /other/ end of the VBAT wires, meaning this can be as modular as Power Strip
  • Since we are wiring I2C lines to this board anyway for undervolting control, using an I2C temperature sensor means there is one less wire going to external boards. Again, this is a big improvement over Power Strip
  • Using (abusing?) the U10 via for our own voltage supervisory purposes just feels so goddamn right! Also, again this is one less wire going to external boards (unless you were doing the wireless U10 relo).
  • aesthetics
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YveltalGriffin

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loopj suggested adding an ALERT interrupt between the TMP1750 and the ATtiny1616, so I did.

alert.png


Explanation: After setting up an undervolt as the I2C controller, the ATtiny will fall back into I2C peripheral mode. Once the Wii takes over as controller, the ATtiny can no longer actively poll the TMP. It would be janky to rely on Hiidra to constantly poll the TMP, detect an overtemp condition, and send a command to the ATtiny to shut down the regs. Instead, the TMP's ALERT pin will send an interrupt directly to the ATtiny, telling it to shut down the system during an overtemp event.

I also finished up the solderpaste stenciling jig PCBs:
thundervolt_jig2.PNG
thundervolt_jig.PNG


Aiming to order everything this weekend! The board is designed right at JLC's min tolerances (3.5/3.5mil) so I'm prepared for them to balk at it :XD:
 
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subierekt

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So theoretically could the 5v reg on the short stack board handle this? So you could really only have 5v/gnd and the data lines if using this in short stack. Not that id really care about undervolting in a non portable like it, just using it as an example.
 

YveltalGriffin

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Yep, Thundervolt will work with any input from 2.5 - 5.5V as long as it can provide enough current. 5V/3A USB-C as used in Wii Micros will be plug and play.

Boards have been ordered and should be here in a week or so!
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YveltalGriffin

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The boards arrived and they look amazing! JLC did a great job.

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Fitment on the Wii motherboard is perfect thanks to @loopj's work on Power Strip. <3

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The jig PCBs fit nicely too. I'm stoked! Can't wait to assemble these.
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YveltalGriffin

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Info dump for those not in the Discord:

Thundervolt rev1 boards have been assembled and tested. All the hardware is fully functional!
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So sleek!

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LP5907UVX solder balls:
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Atmel ICE connected for programming. Thundervolt's amber LED looks awesome!
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Voltages configured to non-standard values via I2C: 750mV, 800mV, 1500mV, and 2800mV


Pics of initial Wii i2c testing, followed by installation and testing on a real mobo. @loopj has written all of the firmware and homebrew stuff from scratch, including the i2c drivers, without Thundervolt hardware! So far there have only been minor bugs, that he's been quick to iron out. What a beast!!!

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Thundervolt will release with a companion homebrew app for configuring undervolt settings, setting the overtemperature threshold, and more. Alex (@supertazon ) is helping out a ton with the GUI and graphics programming. Here is a mockup of the GUI...

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...and how it currently looks on hardware, via direct drive.

app.jpg


I'm also working on Thundervolt rev2 hardware, which adds castellations for easier installation, and INA700s for voltage/current/power sensing on all the voltage rails. This "closes the loop" and allows the Wii to undervolt itself, AND monitor/log its own power consumption. B|

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Many thanks to @loopj and Alex (@supertazon) for all their help thus far! This project is a collaborative effort and a labor of love, and we can't wait to finish it up and release it to all of you!
 
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StonedEdge

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