Digital Hourmeter

[Melanie]

Hmmm... don't quite understand your figures...

1/60=16667uS = $411B based on 1uS tick time (4MHz clock)

$0000-$411B=$BEE5

Use Microsofts Calculator in Scientific mode... you cant do 0-411B in hex directly, so instead do FFFF-411B and just add 1 to your answer.

Setting the clock for a 16667uS count would be...

T1CON.0=0 ' Stop the Clock
TMR1H=$BE ' Set Timer Highbyte
TMR1L=$E5 ' Set Timer Lowbyte
T1CON.1=1 ' Restart the Clock
PIR1.0=0 ' Reset TMR1's Interrupt Flag

If you're returning from an Interrupt then use RESUME otherwise if it's from a subroutine use RETURN.

You may have to adjust the $E5 value slightly to trim your time accurately to account for instruction cycle time in setting the clock etc.

[jmgelba]

Melanie,
I think we have our wires crossed a little.

Are you setting up the timer to count internal pulses? I am trying to count a 60hz 50% duty cycle pulse from the mains supply. When I've counted 21600 of them, I want the counter to reset, send a increment to a counter, and start again.

Therefore, I dont understand why we need to measure 16.67ms. This is the period between highs at the i/p. Time really has nothing to do with it, we just need to get to 21600 and say, ok, im done, reset me please :-)
So thats why I have the numbers in there that I do. Start the counter at 43935, when we've counted 21600 pulses we should be at 65535. The next pulse will set the interupt, and we start again. Well, start the timer at 43936 I guess.

65535 = $FFFF
43935 = $AB9F
21600 = $5460

65535 - 21600 = 43935

According to Microsoft's calculator.
Thanks for the tidbit on the resume command.

Disclaimer:- I know you're not stupid, so the natural conclusion is that I must be LOL. Thanks for your help Mel.

[Melanie]

No, it's my fault... not reading the thread properly from the beginning...

What I told you was valid for the timer keeping it's own time...

But, nevertheless if you want the Timer to count 21600 (or however many) pulses from an external source then yes, it's 65536-21600=43936, or $ABA0 that needs to be preset into TMR1H & TMR1L. Note I'm subtracting from 65536 ($0000 or zero) and not from 65535 ($FFFF), because the interrupt is on the roll from 65535 ($FFFF) to 65536 ($0000).

Look at the T1CON Register for your PIC... you will also have to set TMR1CS for EXTERNAL input and provide your 60Hz pulses on the appropriate T1CKI pin for your PIC.

[jmgelba]

So I am on track with this?
Timer counts up, sets the interupt. Interupt causes CounterA to advance by 1, which increments the digits for the display. Obviously, the segment drive logic is not there yet.



Tenths var word
Units var word
Tens var word
Hundreds var word
Thousands var word
Tenthousands vAR WORD

Gosub SetTimer ' Set the Timer
On Interrupt goto CounterA
PIE1.0=1 ' Enable TMR1 Interrupts

SetTimer:
T1CON.0=0 ' Stop the Clock
TMR1H=$AB ' Set Timer Highbyte
TMR1L=$A0 ' Set Timer Lowbyte
T1CON.1=1 ' Restart the Clock
PIR1.0=0 ' Reset TMR1's Interrupt Flag
Return

CounterA:
' Timer Interrupt Handler
' =======================

Gosub SetTimer ' Set the Timer for next count
Tenths=Tenths+1 ' Increment 1/10TH minute Counter

If Tenths>9 then
Tenths=0
Units=Units+1 ' Increment the Units

If Units>9 then
Units=0
Tens=Tens+1 ' Increment the Tens

If Tens>9 then
Tens=0
Hundreds=Hundreds+1 ' Increment the Hundreds

If Hundreds>9 then
Hundreds=0
Thousands=Thousands+1 'Increment the Thousands

If Thousands>9 then
Thousands=0
Tenthousands=Tenthousands+1 'Increment the Tenthousands

endif
endif
endif
endif
endif
endif
endif
Resume
End

[Melanie]

Ummm.... on track?.... well maybe you're on a siding but you've not reached the main line yet... theory might be there, but reality it won't run - way to go yet...

Tenths var word
Units var word
Tens var word
Hundreds var word
Thousands var word
Tenthousands vAR WORD

Where's the PIC initialisation here? No Registers are configured, no I/O, TMR1 is not set up to accept external pulses...

Gosub SetTimer ' Set the Timer
On Interrupt goto CounterA
PIE1.0=1 ' Enable TMR1 Interrupts

At this point your program runs into a subroutine without calling it. You should have a logical program loop.

SetTimer:
T1CON.0=0 ' Stop the Clock
TMR1H=$AB ' Set Timer Highbyte
TMR1L=$A0 ' Set Timer Lowbyte
T1CON.1=1 ' Restart the Clock
PIR1.0=0 ' Reset TMR1's Interrupt Flag
Return

Your program encounters a Return with nowhere to return to... so at this point it dies - quite apart from the fact it's counting INTERNAL clock ticks.

You've not set any ENABLE/DISABLE to identify which sections of your code will be interruptable, and which sections should be protected from interrupt.

That's just a starter without going into any depth.

[jmgelba]

I realize all the initialization settings are not there! I was just asking if what I posted made any sence. I also realize that there is no program loop, becuase I havent created it. I'm just trying to learn this stuff piece by piece. It easier for me to break it down into sections to figure exactly what is going on before I attempt to write a huge program with a 1000 mistakes only to get disheartened and pay someone to do it for me.

[Dwayne]

Hello Jm,

Jm>>I was just asking if what I posted made any sence. I also realize that there is no program loop, becuase I havent created it. I'm just trying to learn this stuff piece by piece. It easier for me to break it down into sections to figure exactly what is going on before I attempt to write a huge program with a 1000 mistakes only to get disheartened and pay someone to do it for me.<<

Naw, I think we can help you figure it out <smile>..

I am curious... what are you going to use your hour meter for??? I am a pilot, and I am building a new airplane right now... I am going to use a PIC chip as a HOBBS meter for my Engine, as well as a RPM and a possibly a Altimeter/Velocity (if I can find a sensor that is cheap enough). Your project looks almost exactly like mine to many a degree, that is why I ask.

Dwayne