stm32samples/F0-nolib/uart_blink

Code for STM32F030F4 chinese board

• Toggle onboard green LED once per second.
• Echo received by USART1 data (not more than 64 bytes including '\n') on B115200:
  • if PA6 not connected to ground echo text directly
  • otherwice echo it reversly
• Light up LED on PA5 (opendrain) when receive data and turn it off when send.