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?
2 Answers
They often mean that communications do not work properly. The very first bit (the start bit) appears, but the data bits do not. Common reasons for that are:
- Bad connection in ground or data line (high resistance or capacitance)
- Sender's baudrate is way too high (sender sends at 57600, receiver listens at 9600)
- Sender's voltage is too low (1.8V sender sends data to 5.0V receiver)
- Power supply problems (regulator is overloaded or oscillating because capacitors are not big enough)
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\$\begingroup\$ And noise pick up or loose connections could cause spurious start bits. Feel free to add to your answer \$\endgroup\$– KalleMPSep 4, 2015 at 19:21
Nothing, they're just bytes. Why your device produces them and how your terminal emulator interprets them is implementation-specific, but they don't mean anything in a general sense.
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\$\begingroup\$ They are bytes because they cannot be shown (UTF-8 chars). I'll try to give you UTF-8 hex codes for these three. \$\endgroup\$– JuniorSep 4, 2015 at 7:00
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2
11111101
, FE is11111110
, and FF is11111111
. There are lots of1
-level bits on your signal line … \$\endgroup\$