usart1 documentation

examples/usart1.rs

-//! Test the USART1 instance
+//! A simple echo server for the Nucleo 64, stm32f401re
 //!
-//! Connect the TX and RX pins to run this test
+//! The jumpers on the board should be in their default position.
+//! This setting tunnels RX/TX over a VCP on the onboard stlink2-1.
 //!
-//! PA2 (TX), PA3(RX) on the MCU is connected to the pin header CN3
+//! Connect to the VCP at dev/ttyACM0 (or similar) 115200 8N1.
+//!
+//! Todo:
+//!  info on pin header CN3 (TX/RX), howto use
 //#![deny(unsafe_code)]
 #![deny(warnings)]
 //#![allow(warnings)]