Help whit tmr1 on pic16f877a

[aratti]

Hi Don, here my suggestion. If your max encoder count is not bigger of 65535 then you can feed your encoder pulses directly to timer1 input (pin 15 of you 16f877). Timer1 has to be set as a counter using "T1CON = %00000111" and then you have two ways to control your motor.

1) You poll the timer1 register TMR1H and TMR1L to see when the count reaches the desired value to stop the motor.
Or
2) you use DT interrupt (as already suggested) and you just load the count in Timer1 register (you have to load the complement : 65535-desired count) and wait for the overflow. In other words when the count is reached the value of the timer1 counter will be 65535 and adding one pulses it will overflow invocking the interrupt. In this routine (called ISR) you will stop your motor.

If your needed count is greater then 2^16 it it still possibile to use timer1 as a counter but in this case interrupt is mandatory.

Cheers

Al.

[DonLuis]

Hi guys:

Aratti; I already tried tmr1 interrupt on overflow, as you are suggesting, I explained that, on my post on July 21st, it’s just that seem to take too long to stop the motor and I get much more than I am barging for, sort of speech, also tried external interrupts on RB.0, and lastly polling from what I got much better results if you like to take a look to that post, I even included the code I used for each attempt.

Archangel; thank you for that, I already took a look to Darrel’s page and downloaded his .bas files and included, them on the PBP folder, (I feel relief now), but I’ll to try this first, since I got everything setup, and due to that I have fairly good results on polling, using the same encoder disc it measures twice de input because it is counting up on every negative and positive pulse, so just finished while ago a disc with 75 slot’s about half the other one, if still no good output then I try Darrel’s code, I’ll let you all know as soon as I get around it.

[aratti]

I already tried tmr1 interrupt on overflow, as you are suggesting,

I suggested timer1 overflow with a true interrupt (Darrel Taylor interrupt) your code didn't use any interrupt.

You can try to use this simple snippet which uses the timer1 as a counter, without interrupt and works pretty well.

False           con 0
True            con 1
Z0               Var Byte
Cnts            var word
Tape_Len        Var Word

Logic_1         var portXx  ' any available free input

Motor = False
Brake = False
TMR1H = 0
TMR1L = 0

Main_Loop:
If ????? goto  Load_Tape
If ????? goto Set_Tape_L
goto Main_loop

Set_tape_L:
Tape_Len = XXXXX ' encoder pulses derived from the tape lenght desired
return

Start_Motor:
Brake = False
Motor = True
Return

Stop_Motor:
Motor = false
Brake = True
Pause 200
Brake = False
T1CON.0 = False
Return


Load_Tape:
 Cnts = 0
TMR1H = 0
TMR1L = 0
T1CON.0 = true
Resume_Halt:
Lcdout $FE, 1,   "  Press Yy to stop  "
Lcdout $FE, $C0, "--------------------"
Lcdout $FE, $94, "Now Loading Tape ..."
Lcdout $FE, $D4, "Loaded: ",dec Cnts

Gosub Start_Motor

For Z0 = 0 To 100                               ' 100 millisecs delay
pause 1
if Logic_1 = True then Hw_Halt                  ' check if emergency stop is activated
Next Z0

Winding:                                                ' loading start here
Cnts.highbyte = TMR1H
 Cnts.lowbyte = TMR1L
         If Cnts => Tape_Len then 
         gosub Stop_Motor                           ' if count = lenght desired stop motor
         goto Main_Loop
         End If
   if Logic_1 = True then Hw_Halt                ' If emergency stop key pressed stop motor

Lcdout $FE, $D4, "Loaded: ",dec Cnts            ' display updated count
goto Winding

Hw_Halt:
gosub Stop_Motor
Emergency_menu:
1) if ????? then goto Resume_Halt
2) if ????? then goto Main_Loop
goto Hw_Halt

End

Naturally you need to complete the code replacing the parts with ?????? and Xx with reference to your hardware setup.

Cheers

Al.