I have the following 5 bytes in the attached image and need to extract the datetime from it. I understand I'll need to bit shift and maybe use bitwise and's, but fail to get the correct information from the bytes.
2 Answers
Maybe this?
int yearBase = 1993; int year = yearBase + (int) ((bytes[4] & 0xF0) >> 4) | ((bytes[3] & 0xE0) >> 1); int month = (int) (bytes[4] & 0x0F); int day = (int) (bytes[3] & 0x1F); int hour = (int) ((bytes[2] & 0xF8) >> 3); int min = (int) (((bytes[2] & 0x03) << 3) | ((bytes[1] & 0xE0) >> 5)); int sec = (int) ((bytes[1] & 0x1F) << 1) | ((bytes[0] & 0x80) >> 7); int hundreths = (int) (bytes[0] & 0x7F); 
1 Comment
Matthew Lamb
Matt that is given me some good dates, I'll have to test this against the dates that I know. I'll have to track down some data for that, but the above is definitely on the right track, Thank you.
I recently answer a question about bitshifting and integer packing in C#.
May be helper class written in that case can be usefull to you as starting point
public static class BinaryConverter { public static BitArray ToBinary(this int numeral) { return new BitArray(new[] { numeral }); } public static int ToNumeral(this BitArray binary) { if (binary == null) throw new ArgumentNullException("binary"); if (binary.Length > 32) throw new ArgumentException("must be at most 32 bits long"); var result = new int[1]; binary.CopyTo(result, 0); return result[0]; } public static BitArray Take (this BitArray current, int length ) { if (current.Length < length) throw new Exception("Invalid length parameter"); List<bool> taken = new List<bool>(); for (int i = 0; i < length; i++) taken.Add(current.Get(i)); return new BitArray(taken.ToArray()); } public static BitArray Shift (this BitArray current, int length ) { if (current.Length < length) throw new Exception("Invalid length parameter"); List<bool> shifted = new List<bool>(); for (int i = 0; i < current.Length - length; i++) shifted.Add(current.Get(length + i)); return new BitArray(shifted.ToArray()); } public static BitArray FitSize (this BitArray current, int size) { List<bool> bools = new List<bool>() ; bools = bools.InitBoolArray(size); for (int i = 0; i < current.Count; i++) bools[i] = current.Get(i) ; return new BitArray(bools.ToArray()); } public static List<bool> InitBoolArray(this List<bool> current, int size) { List<bool> bools = new List<bool> (); for (int i = 0; i < size; i++) bools.Add(false); return bools ; } Here the reference to that answer Dynamic Bit Shifting / Unshifting
At the link above is displayed how pack small number on the same integer, your five bytes is pretty close to that question
Yare calculated. Are they a single value with bits concationated or is each one represent a single digit of the last two digits of a year? The fact that they are separated from each other makes me think each is a digit, but you can only represent 0-7 with the 3 bits it uses inByte 3. If they are concatenated that gives you 0-127, so you could use that for 0-99