Newbie Question

[Travin77]

Thanks for the code. I almost got it to work i think. The problem is I don't know how to adjust/configure my registers. I looked at both the 12f625 and 16f629a datasheets to compare the original code to the updated code but my pic has alot registries naturally. I am also not sure if I have the crystal pins setup correctly or not. Here is my code and schematic. The oscillator has built in caps. I also forgot to ask what code I would need to make something happen at a given time. Thanks for any help you all can give.

[DynamoBen]

Several things:

1) First your crystal is connected incorrectly based on the text file. On a 16F628 the crystal needs to be tied to pins 15 and 16. (see datasheet for details)

2) Depending on your baud rate you may want to move the speed of your crystal up. At 9600 baud I usually use 16 mhz crystal.

3) Here is an example of a typical Device programming Options :

@ DEVICE pic16F628, HS_OSC ' System clock Options
@ DEVICE pic16F628, WDT_ON ' Watch Dog Timer
@ DEVICE pic16F628, PWRT_ON ' Power-on timer
@ DEVICE pic16F628, BOD_ON ' Brown-out detector
@ DEVICE pic16F628, MCLR_OFF ' Master Clear Options
@ DEVICE pic16F628, LVP_OFF ' Low-voltage programming
@ DEVICE pic16F628, CPD_OFF ' Data Memory Code Protect
@ DEVICE pic16F628, PROTECT_OFF ' Program Code Protections

NOTE: If you noticed above I have clock option set to HS not XT. At 16mhz this is considered High-Speed.

4) When using a crystal don't forget to define the speed:
DEFINE OSC 16 ' 16mhz XTAL

5) The word "SYMBOL" is unneeded when you are defining constants. Use the follwing instead:
line1 CON 128

6) TRISB=%11111111 ' PORTB all Inputs
TRISB=%00000000 ' PORTB all Outputs
TRISB = %00000001 ' PORTB.0 PIN input for button

These things should help get you running.

[paul borgmeier]

With your code posting, if you fix the crystal location as DynamoBen suggested (and makd sure to add the caps to GND) and delete the “INTCONB=0 'interrupts off”
line, the clock portion with display should work great as is.

Note - for the code you have, you need to use 4MHz xtal. You could adjust the algorithm for 16MHz xtal if desired. One last thing, to “use the clock”, you can put something like

If HH = 4 then ‘ turn on portb.1 at 4:15 and turn it off at 4:30
If MM = 15 then portb.1=1
If MM = 30 then portb.1=0
Endif

In the section labeled “do something here”

Again, Good Luck,

Paul Borgmeier
Salt Lake City, Utah
USA

[Travin77]

I also have a 20mhz crystal. Would this be better to use? Also, I really don't know how to adjust the algorithim for any change in crystal speed, how would you do this? Additionally, on ProtectionsDynamoBen's post, do I need to include the following in the program:
@ DEVICE pic16F628, HS_OSC ' System clock Options
@ DEVICE pic16F628, WDT_ON ' Watch Dog Timer
@ DEVICE pic16F628, PWRT_ON ' Power-on timer
@ DEVICE pic16F628, BOD_ON ' Brown-out detector
@ DEVICE pic16F628, MCLR_OFF ' Master Clear Options
@ DEVICE pic16F628, LVP_OFF ' Low-voltage programming
@ DEVICE pic16F628, CPD_OFF ' Data Memory Code Protect
@ DEVICE pic16F628, PROTECT_OFF ' Program Code
I noticed after time setup, the program changes the contitions of some of the registries. Do I need to do the same and what should they be?

Sorry for being a hassle but I really appreciate you alls help on this.

Thanks

[DynamoBen]

The @ DEVICE statements are always at the top of my program. It automatically sets up my programmer when I load the file.

If you change the crystal speed you will need to alter your timing. For now I would just mess around with 4mhz until you find your way around. If it works then great!

The reason you need to adjust as you change the crystal speed is because the timer function is directly proportional to the crystal. Faster the crystal the faster the timer function will interrupt. If you move to a 20mhz crystal your interrupt will be 5 times faster. So instead of 1 second in your clock program it will be 200ms.

One thing to remember, most everyone here learned by reading the manual and experimenting. You may have to experiment to answer some of your questions. You may want to pick up Nuts and Volts magazine this month. They are doing a series on PICs and PICBasic, very good if you’re just starting out.
http://www.nutsvolts.com/

[Travin77]

Thanks for the help, I just dont understand how it works. I am assuming that if I increase my crystal speed to 20 mhz that I need to change my prescaler or am I way off? Can you explain how it works for me please? I have read the data sheet and understand how to adjust the registers I just don't know how to figure out what they should be.

[DynamoBen]

Sort of.

Check this piece of software out. It really helped me to understand the timers and interrupt times.

http://users.picbasic.org/projects/P...icTimerCal.htm

BTW: The datasheet does have a calculation in it. Honestly I never understood it.