Function open 

pub fn open(path: &str, baud_rate: u32) -> Result<Box<dyn SerialPort>>

Available on crate feature serial only.

Open a serial port with defaults suitable for Marlin BFT:

• 8N1
• read timeout 100 ms (so the host can pump retransmits without hanging in read)
• DTR/RTS not asserted explicitly — the OS-default behaviour applies