UberNewbie can't set his clock...

[mackrackit]

When does the shift command actually change the data in BCDByte?

It is my understanding that the shift command in a case like this will not change the data.
It only tells what part of the value to use in the calculation.

[Melanie]

OK, lets break this down...

DecimalByte=(BCDByte>>4)*10+(BCDByte & $0F)

The calculations in the brackets will be perfomed first, and the results stored in a PICBasic variable behind the scenes. BCDByte is unchanged - just as well because we refer to it twice, once to access the top four bits, and once to access the bottom four bits.

Thereafter, PBP follows mathematical rules of priority... ie Multiplication and Division are performed before addition ans subtraction. Because items in brackets are always calculated from the centre out, and each set of brackets is it's own self-contained world, the result of the formula below, will be the same as that above.

DecimalByte=(BCDByte & $0F)+((BCDByte>>4)*10)

However, you do have an extra set of brackets there... but PBP actually resolved the formula without any additional penalty. Might not be so lucky on another occasion.

[Byte_Butcher]

Thanks again Melanie,
Hmmm, I think I almost understand what's going on with that code. I must actually be learning something.

I ended up with this, from the code you supplied and it works excellent.

increminute: 

        rtcmathtemp =(rtcmin>>4)*10+(rtcmin & $0F)  'convert BCD minutes into Decimal minutes
        
        rtcmathtemp=rtcmathtemp+1   'increment by 1
        If rtcmathtemp>59 then      'If minutes exceeds 59
        rtcmathtemp=0               'reset to 0
        endif
  
        rtcmin=((rtcmathtemp DIG 1)<<4)+rtcmathtemp DIG 0 'convert Decimal back to BCD

        gosub settime
       
        return

[Byte_Butcher]

Sigh, well I seem to have a new problem. Although I'm obviously able to read/write to the DS1302 in "burst" mode, I seem to be having a problem addressing individual registers.

For instance, I need to turn the trickle charger on...
I *thought* it was as simple this:

        rst = 1

        'Set Battery charger on and set to "1 diode, 2Kohm"
        Shiftout IO, SCLK, LSBFIRST, [$90, $A5]  ' Set charger   [$90, $A5] 
 
        RST = 0

But that doesn't seem to do it for me.

Anyone got the patience to help me along a little further....

p-p-p-please?

Thanks!

Steve

[Archangel]

Hi Steve, check uot pages5/ 6 of this data sheet, it says: DS 1302 powers up with trickle charger disabled and only a pattern of 1010 will enable charger. http://forums.parallax.com/forums/attach.aspx?a=26594 HTH

[Byte_Butcher]

Thanks Joe,
You can't imagine how many times I've read the data sheet.... (it's been open on my desktop for days now)
I'm clearly not quite understanding yet.

Yes, a pattern of 1010 turns on the charger, and the other 4 bits of the byte set the charge rate.

So what ( I think) I want to send is 10100101 which should tun on the charger and set it to "1 diode, 2Kohm" operation. In HEX, that's $A5, right?

So I've sent $90, which should be the register address for the charger, and $A5, which should be the code to turn it on and set it to my chosen charge mode. I even tried sending the data in binary, like so:

        rst = 1

        'Set Battery charger on and set to "1 diode, 2Kohm"
        Shiftout IO, SCLK, LSBFIRST, [$90, %10100101]  ' Set charger   [$90, $A5] 
 
        RST = 0

but with the same (no) result.

What am I doing wrong? (please!)

Thanks,
Steve

[Byte_Butcher]

Ahh, never mind, I figured it out...

Setting up the trickle charger is the first task task I ask of the DS1302, and I just needed to pull the reset line LOW first, before I yank it high and move the data.
All I was missing was "rst = 0" up front:

 
       rst = 0
       rst = 1

        'Set Battery charger on and set to "1 diode, 2Kohm"
        Shiftout IO, SCLK, LSBFIRST, [$90, %10100101]  ' Set charger   [$90, $A5] 
 
        RST = 0

Thanks again to everyone!

Steve