[펌] 라즈베리 파이 - UART 연결

https://periar.tistory.com/230#google_vignette

https://neighborhoodunclelab.tistory.com/entry/%EB%9D%BC%EC%A6%88%EB%B2%A0%EB%A6%AC-%ED%8C%8C%EC%9D%B4%EC%97%90%EC%84%9C-UART-%EC%82%AC%EC%9A%A9%ED%95%98%EA%B8%B0