[aprssig] Dear Mr Kenwood (MicE decoding)
Robert Bruninga bruninga at usna.eduMon Dec 28 23:21:28 UTC 2009
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>> Decoding the Mic-E format is very simple, >> and especially in a pic chip. A simple offset >> subtraction of the binary value of the Mic-E >> character yields the numeric value of latitude or >> longitude etc... > > "Especially in a PIC chip?" How do you figure? Six bytes of Latitude: (0-9 or A-J or P-Y) 1) If > "9" then set the approprate msg/flag bits 2) If > $70 then Subtract $70 hex from the byte. 3) If > "@" then subtract $41 hex from the byte 3) Result is decimal digit of latitude. Done Base91 Encoding of Longitude: 1) for each byte, subtract 28 decimal 2) result is two digits of longitude. 3) do 3 times. 4) Add 100 degrees if 100 degflag is set 5) Subtract 60 if minutes digits are > 60 Done. Plus a little cleanup here and there... It was designed to be a pretty simple manipulation of bits. A table was never intended. That was just how Ian decided to represent the algorithm in the spec making it appear overly complex when in fact, it is a very simple offset of bits. Bob, Wb4APR
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