* Ok, after doing some digging and experimenting, the above appears to be straightfwd, although I have to change several settings.

To sleep:
```rust
scl.mode(PinMode::Output, &mut gpiob.regs);
scl.output_type(OutputType::PushPull, &mut gpiob.regs);
scl.pull(Pull::Floating, &mut gpiob.regs);
scl.set_low();
```

To wake, and reset to normal I2C behavior:
```rust
scl.mode(PinMode::Alt(AltFn::Af4), &mut gpiob.regs);
scl.output_type(OutputType::OpenDrain, &mut gpiob.regs);
scl.pull(Pull::Up, &mut gpiob.regs);
```

I initially tried to just set the pull low without changing to PushPull, and it still stayed high. Might be some steps I can skip, but not sure