timer0 - counter

[Nobody/Anonymous]

Hi to all

I pretend to count how many times  a pin (ra4) goes to 0V or V+. My idea in the future will be to build an anemometer or an frequency counter or something based on that. I know that timers are excelent to do the job but until now I wasn't able to make a test with  a switch.
I have a resistor from RA4 to V+ and a switch to 0V. I supose that when I press the switch the timer will be incremented and then I can display Timer0 value to my 7seg.display.
Until now none of my approaches give me a good result.
Can anyone give me an idea how to make timer0 work?
Thank you all
Eduardo Freitas
the code I'm using is this:

'=================================================
'Chip model
#chip 16F628A, 4
#config OSC = INTOSC_OSC_NOCLKOUT, WDT = OFF
'config OSC = XT, WDT = OFF

#define StartUpDelay 100 ms

'setting the 7 segment display with 2 displays
#define displaycount 4

#define DispSelectA nop 
#define DispSelectB nop
#define DispSelectC nop
#define DispSelectD nop

#define Display1 PortA.0
#define Display2 PortA.1
#define Display3 PortA.2
#define Display4 PortA.3
#define waitDisplay wait 6 ms

#define DisplayPortA PORTB
#define DisplayPortB PORTB
#define DisplayPortC PORTB
#define DisplayPortD PORTB
'#define DispSelectA set PORTA.0 ON set PORTA.1 OFF
'#define DispSelectB set PORTA.0 OFF set PORTA.1 ON

dir PORTB.0 out
dir PORTB.1 out
dir PORTB.2 out
dir PORTB.3 out
dir PORTB.4 out
dir PORTB.5 out
dir PORTB.6 out
dir PORTB.7 out

dir PORTA.0 out
dir PORTA.1 out
dir PORTA.2 out
dir PORTA.3 out
dir PORTA.4 in

InitTimer0(Ext,PS0_1/2)

Startup:
Wait StartUpDelay

'MAIN PROGRAM
dataCount=0
Main:
        ' First time value =0, after that count pulses on RA4(remember prescaler /2)
    dataCount=timer0
    ClearTimer 0

'START COUNT PULSES on pin

    Centenas=dataCount/100
    Dezenas=(dataCount %100)/10
    Unidades=dataCount % 10
    for icounter = 1 to 128
          Set Display2 ON:Set Display3 ON:Set Display4 ON:Set Display1 OFF
          displayvalue 1, unidades
          waitDisplay
          Set Display1 ON:Set Display3 ON:Set Display4 ON:Set Display2 OFF
          displayvalue 2, dezenas
          waitDisplay
          Set Display1 ON:Set Display2 ON:Set Display4 ON:Set Display3 OFF
          displayvalue 3, centenas
          waitDisplay
          Set Display1 ON:Set Display2 ON:Set Display3 ON:Set Display4 OFF
          displayvalue 4, dataCount
          waitDisplay
    next
    iCounter=1
    'Clear all
    unidades=0
    dezenas=0
    centenas=0

    'clear display
    Set Display1 ON:Set Display2 ON:Set Display3 ON:Set Display4 ON
    displaychar 1, "0"
    Set Display1 ON:Set Display2 ON:Set Display3 ON:Set Display4 ON
    displaychar 2, "0"
    Set Display1 ON:Set Display2 ON:Set Display3 ON:Set Display4 ON
    displaychar 3, "0"
    Set Display1 ON:Set Display2 ON:Set Display3 ON:Set Display4 ON
    displaychar 4, "0"
    wait 1 s
Goto Main
'================================================

[Santiago]

Hi Eduardo.

I think there is a bug in the Timer0 function in timer.h that afect only to the counter mode

You can try this function: copy in yor code afther "Goto Main" and use "MyInitTimer0 (Ext, PS0_1/2)" instead of "InitTimer0(Ext,PS0_1/2)":

Sub MyInitTimer0(TMR0Source, TMR0Pres) #NR

    OPTION_REG = OPTION_REG AND 192

    if TMR0Source = Ext THEN SET OPTION_REG.T0SC ON
    OPTION_REG = TMR0Pres OR OPTION_REG 

    clrwdt

End Sub

If this works, you can edit your ../include/lowlevel/timer.h file, look for the function "Sub SInitTimer0" (line 152) and change it for this one:

Sub Sub SInitTimer0
    OPTION_REG = OPTION_REG AND 192
    if TMR0Source = Ext THEN SET OPTION_REG.T0SC ON
    OPTION_REG = TMR0Pres OR OPTION_REG 
    clrwdt
End Sub

Regards.

[Nobody/Anonymous]

Thank you Santiago,

The change result! I changed the OPTION_REG.T0SC to OPTION_REG.T0CS and now is counting!

Regards

[Santiago]

You're right... was a typo error... but you realized it.

Sorry for the mistake.

[Edward LaBudde]

Santiago, there is an error in your code:

if TMR0Source = Ext THEN SET OPTION_REG.T0SC ON

Should read:

if TMR0Source = Ext THEN SET OPTION_REG.T0SE ON

Regards, Ed.

[Nobody/Anonymous]

Sorry Edward, but that precisely is the error in the original GCBasic code, the clock source is selected in OPTION_REG.T0CS register, not in OPTION_REG.T0SE register, that is for select rising or falling edge when in counter mode.

Then as Eduardo Freitas said, there was an error in my code but was this:

if TMR0Source = Ext THEN SET OPTION_REG.T0SC ON 

Should read:

if TMR0Source = Ext THEN SET OPTION_REG.T0CS ON

_________________________________________________
You can check it in the datasheet:

bit 7   RBPU

bit 6   INTEDG

bit 5   T0CS: TMR0 Clock Source Select bit
        1 = Transition on T0CKI pin
        0 = Internal instruction cycle clock (CLKO)

bit 4   T0SE: TMR0 Source Edge Select bit
        1 = Increment on high-to-low transition on T0CKI pin
        0 = Increment on low-to-high transition on T0CKI pin

bit 3   PSA: Prescaler Assignment bit
        1 = Prescaler is assigned to the WDT
        0 = Prescaler is assigned to the Timer0 module

bit 2-0 PS2:PS0: Prescaler Rate Select bits

[Edward LaBudde]

Santiago, I got an error compiling it the way it was: TOSC not previously defined.  Works fine after I changed it to TOSE as above.  Regards, Ed.

[Santiago]

Edwuard, in my previous post i said (read carefully):

___________________________________________________

Then as Eduardo Freitas said, there was an error in my code but was this:

if TMR0Source = Ext THEN SET OPTION_REG.T0SC ON 

Should read: 

if TMR0Source = Ext THEN SET OPTION_REG.T0CS ON
___________________________________________________

TOSC bit doesn't exist, the correct name is TOCS.

This error only appears when using External clock source, when using internal clock there is no problem.

Greetings.

[Santiago]

Sorry i forgot to say, the correct is T0CS:
0 = number
O = capital letter

The correct is with number: T0CS = Timer 0 Clock Source