Trouble simulating DS1307 RTC chip

[andrewgodfrey]

Hi.
I am planning to design a countdown timer with a picaxe 18x ,7 segment displays and a DS1307 real time clock chip.
As I do not yet have a DS1307,I have been experimenting with the Picaxe VSM program.

The program below has replaced the sample program that comes with the VSM program called "AXE110 datalogger.bas", and I have been using the schematic of the same name.


When I run the program, the lcd display shows hours:min:sec.

But the seconds value can suddenly jump several seconds and count to 100 instead of only 59.

Have I made a mistake with my program, or is there a bug in the VSM simulator?

i2cslave %11010000, i2cslow, i2cbyte
    
writei2c 0,($00,$00,$1,$03,$25,$12,$03,$10)  'Set time to 1:00:00 am on 25/12/03
        
Showtime:
 readi2c 0,(b0,b1,b2)
 serout 6,t2400,(254,128,#b2,":",#b1,":",#b0) 
goto Showtime

Thanks,
Russell.

 

[hippy]

The DS1307 values are held as BCD ( binary coded decimal ) where each byte is split into two 4-bit nibbles each of which represent a digit; so 12 is held as $12 which is two separate digits $1 and $2. That $12 is 18 in decimal which is what the # in the SEROUT commands give. You need to convert BCD digit pairs to decimal digits before using them ...

b0 = $12
BcdToAscii b0, b11, b12, b13
SerOut 6, T2400, ( b11, b12, b13 )

should show "0", "1" and "2".

 

[andrewgodfrey]

Thanks for the reply. It did help me understand the data output by the DS1307.
But the code you supplied actually gave me a syntax error using Picaxe VSM.

Would you please be able to supply code to convert the seconds value read from the DS1307 into decimal.
I expect this code would then also convert minutes and hours with a little modification.

I was able to get the folowing code to show "12" on the LCD display

start:

b0 = $12
BcdToAscii b0, b11, b12
SerOut 6, T2400, (254,128, b11, b12)

goto start

 

[hippy]

My mistake, and apologies for that; I confused BCDTOASCII with the syntax of BINTOASCII. As you have it is how it should be.