```
the following trait bounds were not satisfied:
             `Tx<stm32f4xx_hal::stm32::USART1>: stm32f4xx_hal::embedded_hal::blocking::serial::write::Default<_>`
             which is required by `Tx<stm32f4xx_hal::stm32::USART1>: cortex_m::prelude::_embedded_hal_blocking_serial_Write<_>`
```