Lookup command and hex numbers?

mmccarty

I'm pulling time and date from a RTC and trying to use the lookup command to store times for daily timed events, but I am running into problem with the dates stored as hex numbers. When I use the "day" variable as the index for the lookup command it counts over by the decimal equivalent. (29th day of the month counts over 41 places instead of 29). Am I missing something simple here or do I need to convert the hex day into a decimal index variable beforehand? How?

Carl Hayes

They aren't stored as hex numbers. They're stored as BCD numbers. Isolate the high-order four bits, which represent the tens digit of a decimal representation; multiply it by ten; and then add the low-order four bits, which represent the units digit. That gives you the binary (or hex, if you prefer) equivalent of the BCD number you get out of the RTC.

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· -- Carl, nn5i@arrl.net

mmccarty

Thanks for the help, I have it working:

indx = (date.NIB1 * 10) + date.NIB0

The next question:

I have times stored in a table in a four digit format (1545, 1600, 1830). What would the best way to convert into separate hours and minutes variables to compare to the RTC for alarm events?

-Mac, KB9HV

Zoot

Not sure that code will give accurate results. Try this:

time var Word
hrs VAR Byte
mins VAR Byte
hrs = time/100
mins = time//100

Personally, I would do your table in BCD as HEX rather decimal, then you can just deal with the nibs:

TimeTable DATA Word $1600, Word $0500, Word $1330, Word $1200

FOR idx = 0 TO 3
  READ TimeTable+(idx<<1), Word time
  hrs = time.NIB3 * 10 + time.NIB2
  mins = time.NIB1 * 10 + time.NIB0
  DEBUG "The time is ", DEC2 hrs, ":", DEC2 mins, CR
NEXT

But you could leave it BCD especially if you are using an RTC that is also BCD -- you can just compare the "read" word and an assembled BCD word from the RTC -- greater than, less than, equal to, etc. and it will work just fine as Hex words. If you need to compare just hours or just mins, you could use the high and low bytes.

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mmccarty

Thanks all for the help. The code that was posted did work, although I'm not sure why. (That message seems to have been deleted). Zoot's code had me smacking myself in the head, fairly obvious, y'all make this seem easy... Although as Zoot stated I didn't really need to do a conversion, just do the table in BCD and compare apples to apples:

offtime is the times in the lookup table and hrs and mins is the time from the RTC:

IF offtime.BYTE1=hrs AND offtime.BYTE0=mins THEN
DEBUG HOME, "TIMES UP!!!"