3. Implement drivers for the Nucleo 64, stm32f401re/stm32f411re, similar to the f3/bluepill support crates. Most or all of the peripherals should be supported
* GPIO
* UART over USB using the ST-Link v2
* DMA
* Timers for e.g.
* Microsecond counter
* PWM generation
* Rotary encoder
* SPI
* I^2C
4. The stm32f4 supports higher clock frequency than the default 16 MHz. Implement a simple way of setting it to the maximum of 84 MHz for the stm32f401re and 100 MHz for the stm32f411re, or any valid lower value (configured using the PLL).
5. Create a demo using the RTFM core and some external peripheral such as an IMU or Bluetooth device. The demo should show how to use the RTFM core for safe concurrency and demonstrate different peripherals such as GPIO, USART, DMA, SPI etc.
### Documentation
[F3 Rust support crate](https://github.com/japaric/f3)
[Blue-pill Rust support crate](https://github.com/japaric/blue-pill/)