M9names[m]: > <@9names:matrix.org> works fine for me with rev c of that board, with a few adjustments:
> 
> ```
> diff --git a/.cargo/config.toml b/.cargo/config.toml
> index 73f2ab3..e9d3d58 100644
> --- a/.cargo/config.toml
> +++ b/.cargo/config.toml
> @@ -1,5 +1,5 @@
>  [target.thumbv7em-none-eabihf]
> -runner = 'probe-run --chip STM32F411CEUx'
> +runner = 'probe-rs run --chip STM32F429ZITx'
>  rustflags = [
>    # `flip-link` moves stack at the end of flash
>    #"-C", "linker=flip-link",
> diff --git a/Cargo.toml b/Cargo.toml
> index 48a4f6f..2ef402f 100644
> --- a/Cargo.toml
> +++ b/Cargo.toml
> @@ -544,7 +544,7 @@ required-features = ["otg-fs", "usb_fs"] # stm32f407
>  
>  [[example]]
>  name = "usb-serial-poll"
> -required-features = ["otg-fs", "usb_fs"] # stm32f401
> +required-features = ["otg-fs", "usb_hs"] # stm32f401
>  
>  [[example]]
>  name = "ws2812-spi"
> diff --git a/examples/usb-serial-poll.rs b/examples/usb-serial-poll.rs
> index acce819..716d008 100644
> --- a/examples/usb-serial-poll.rs
> +++ b/examples/usb-serial-poll.rs
> @@ -6,7 +6,7 @@
>  use panic_halt as _;
>  
>  use cortex_m_rt::entry;
> -use stm32f4xx_hal::otg_fs::{UsbBus, USB};
> +use stm32f4xx_hal::otg_hs::{UsbBus, USB};
>  use stm32f4xx_hal::{pac, prelude::*};
>  use usb_device::prelude::*;
>  
> @@ -20,16 +20,17 @@ fn main() -> ! {
>  
>      let clocks = rcc
>          .cfgr
> -        .use_hse(25.MHz())
> +        .use_hse(8.MHz())
>          .sysclk(48.MHz())
>          .require_pll48clk()
>          .freeze();
>  
>      let gpioa = dp.GPIOA.split();
> +    let gpiob = dp.GPIOB.split();
>  
>      let usb = USB::new(
> -        (dp.OTG_FS_GLOBAL, dp.OTG_FS_DEVICE, dp.OTG_FS_PWRCLK),
> -        (gpioa.pa11, gpioa.pa12),
> +        (dp.OTG_HS_GLOBAL, dp.OTG_HS_DEVICE, dp.OTG_HS_PWRCLK),
> +        (gpiob.pb14, gpiob.pb15),
>          &clocks,
>      );
> ```
> 
> then just
> `cargo run --release --example usb-serial-poll --features otg-fs,usb_hs,stm32f429`

👀