I have a 56 byte register available on some eeprom that I'd like to store engine hours with. Currently I just use 3 bytes to increment a 60 second timer and then download the information (the number rarely exceeds 9999 minutes before it transmits).
The problem is that I need to associate a date with this. Every time the vehicle is started I need to start my hours recording, but I need to determine which hour that hour was incremented on.
So if I have a byte[56] array, what would the be the easiest way to store a date (or just an hour of the date), followed by a number, and be able to tell them apart?
For transmitting, I'd need a way to iterate through the array and extract the date or hour, and the hours count.
Any ideas for this would be great, thanks a ton.
End results on a report would look similar to:
06:00 - 38 minutes 09:00 - 60 minutes 10:00 - 60 minutes etc
Okay here is an idea of a scheme to fit all the data you need in your 56 bytes (in fact we can fit upto 11 dates and times into 56 bytes):
Assuming you don't expect this system to last more than a thousand years we can define the first part of the year as i.e. year 2013 is split into two, the epoch and year.
Now you could simply use 7 bytes and increment the values of each and would allow you to store upto 8 dates and times but you could create a struct and bit bang the individual bits to compact it down further allowing you to cramm it into 40 bits (or 5 bytes) allwing you 11 dates.
You could also drop the epoch if you are really cramming but the above scheme will allow you to work with dates upto 3199.
I am sure there are other and more compact ways i.e. number of milliseconds since 01.01.1970 upto say a few years in the future might reduce it by a few bits but reduce the longevity of your code but I haven't had a look at the actual values.
Some example code (Have updated to use BitArray as bool is internally a byte(?!) but BitArray is actually bits... Very important in OPS case.:
OP should note that I believe you are wanting to store the amounts of minutes driven in each hour BUT this would then require a whole lot more space (a record for each hour they have driven in or a start and stop record for each day indicating the minute they started and stopped (a stop has to come after a start afterall). The code below will allow you to record how many minutes have been driven in a given day.
using System;
using System.Collections;
namespace BitBangingDate
{
class Program
{
static void Main(string[] args)
{
CompactDateManipulator x = new CompactDateManipulator();
Console.WriteLine(x.ToString());
x.Month = 7;
x.Day = 27;
x.Minute = 1234;
Console.WriteLine(x.ToString());
var bitArr = x.GetCompactedArray();
CompactDateManipulator x1 = new CompactDateManipulator();//create new blank date to test whether can be reiitialised from BitArray
x1.ReinitialiseDateFromBitArray(bitArr);
Console.WriteLine(x1.ToString());
}
}
class CompactDateManipulator
{
CompactDate _date = new CompactDate();
public int Month
{
get
{
return BoolArrayToInt(_date.month);
}
set
{
IntToBoolArray(ref _date.month, value);
}
}
public int Day
{
get
{
return BoolArrayToInt(_date.day);
}
set
{
IntToBoolArray(ref _date.day, value);
}
}
public int Minute
{
get
{
return BoolArrayToInt(_date.minute);
}
set
{
IntToBoolArray(ref _date.minute, value);
}
}
public BitArray GetCompactedArray()
{
return _date.GetFullArray();
}
public void ReinitialiseDateFromBitArray(BitArray arr)
{
_date.SetDate(arr);
}
//utility methods
void IntToBoolArray(ref bool[] bits, int input)
{
var len = bits.Length;
for (int i = 0; i < len; i++)
{
bits[i] = (input & 1) == 1 ? true : false;
input >>= 1;
}
}
int BoolArrayToInt(bool[] bits)
{
if (bits.Length > 32) throw new ArgumentException("Can only fit 32 bits in a int");
int r = 0;
for (int i = 0; i < bits.Length; i++)
{
if (bits[i]) r |= 1 << i;
}
return r;
}
public override string ToString()
{
return String.Format("Stored Date mm/dd/ss: {0}/{1}/{2}", Month, Day, Minute);
}
}
class CompactDate
{
//Layout Month(5) Day(9) Minute (12)
// 11111 111111111 111111111111
public bool[] month = new bool[5];
public bool[] day = new bool[9];
public bool[] minute = new bool[12];
public BitArray GetFullArray()
{
int fullLen = month.Length + day.Length + minute.Length;
BitArray full = new BitArray(fullLen);
int index = 0;
for (int i = 0; i < month.Length; i++,index++)
{
full.Set(index,month[i]);
}
for (int i = 0; i < day.Length; i++, index++)
{
full.Set(index, day[i]);
}
for (int i = 0; i < minute.Length; i++, index++)
{
full.Set(index, minute[i]);
}
return full;
}
public void SetDate(BitArray arr)
{
int index = 0;
for (int i = 0; i < month.Length; i++, index++)
{
month[i] = arr.Get(index);
}
for (int i = 0; i < day.Length; i++, index++)
{
day[i] = arr.Get(index);
}
for (int i = 0; i < minute.Length; i++, index++)
{
minute[i] = arr.Get(index);
}
}
}
}