# UART weird characters

What FD, FE and FF hex values of chars represent in UART communication? For some time my UART won't work, and always returning me those three?

• Are both DTE and DCE set to matching baud rate, character length, parity, stop bits (e.g. 9600 8N1 for example)? When was the system previously working? What could have changed? What data was expected and how is it encoded before sending to UART? (UART only sends raw data, regardless of what encoding is used.) – MarkU Sep 4 '15 at 7:18
• One common beginner mistake is not to have GND between DTE and DCE connected, wich can lead to non-working or unreliable data transfer. – Rev1.0 Sep 4 '15 at 7:19
• In binary, FD is 11111101, FE is 11111110, and FF is 11111111. There are lots of 1-level bits on your signal line … – CL. Sep 4 '15 at 8:08
• If you are expecting character data, the bytes FE and FF are used in various combinations as a BOM to inform the reader that the following characters are/are not Unicode characters. – Roger Rowland Sep 4 '15 at 9:11