LAB-X1 keypad/timer

I wrote this for someone else wanting a dual background timer with keypad entry to enable/disable individual timed outputs. Figured maybe someone would find it handy - or learn from it.

It runs on the LAB-X1 experimenter board from MeLabs. You can find these here (http://store.melabs.com/cat/boards.html).

This responds to a keypress very quickly, and there's plenty of room for more code in the main loop.

Code:

---

' Name        : CNTDWN_1934X.pbp
' Compiler    : PICBASIC PRO Compiler 2.6
' Assembler  : MPASM
' Target PIC  : 40-pin 16F1934 or similar
' Hardware    : LAB-X1 Experimenter Board
' Oscillator  : 4MHz external crystal
' Keywords    : IF THEN ELSE, FOR NEXT, LCDOUT, WHILE WEND
' Description : PICBASIC PRO program to demonstrate using Timer1 assembly
' interrupts for dual countdown timers in the background. Interrupt periods
' are approximately 100mS intervals with a 4MHz oscillator.
'
' Note: Open the 16F1934.INC file in your PBP directory, and comment out the default
' __config settings.
Asm
  __config _CONFIG1, _FOSC_XT & _WDTE_SWDTEN & _PWRTE_ON & _MCLRE_ON & _BOREN_ON & _IESO_ON & _FCMEN_ON
  __config _CONFIG2, _PLLEN_OFF & _LVP_OFF & _VCAPEN_OFF & _STVREN_ON & _BORV_25
Endasm
 
' Define LCD pins
Define LCD_DREG  PORTD
Define LCD_DBIT  4
Define LCD_RSREG PORTE
Define LCD_RSBIT 0
Define LCD_EREG  PORTE
Define LCD_EBIT  1
 
Asm
#Define Alarm PORTD ; define port for outputs in interrupt handler
#Define Out1 0      ; output1 pin on RD0
#Define Out2 1      ; output2 pin on RD1
Endasm
 
Define INTHAND TmrInt ' point to assembler interrupt handler
 
' setup vars
Tick1 Var Byte Bank0 System  ' Tick counter for alarm1. 255 * 100mS MAX
Time1 Var Byte Bank0 System  ' # of 100mS ticks to compare with Tick1
Tick2 Var Word Bank0 System  ' Tick counter for alarm2. 65,535 * 100mS MAX
Time2 Var Word Bank0 System  ' # of 100mS ticks to compare with Tick2
 
TmrFlag Var Byte Bank0 System ' last 2-bits indicate timer enabled or expired
State  Var Bit  Bank0 System ' state var to indicate LCD needs updating.
IocFlag Var INTCON.0    ' portb int-on-change flag bit
TmrFlag = %00000011    ' 1 = enabled. 0 = expired. start enabled.
State = 1
 
  ' set output "on" times below by adjusting values in Time1 & Time2
  Time1 = 100  ' 100 * 100mS = 10 seconds (255 MAX)
  Time2 = 600  ' 600 * 100mS = 60 seconds (65535 MAX)
 
  ' clear interrupt tick counters
  Tick1 = 0    ' clear Tick1 count
  Tick2 = 0    ' clear Tick2 count
  Goto Init    ' jump to hardware initialization routine
 
' ===========\ Assembly Interrupt Handler /=========== ' 
Asm
TmrInt                ; registers in bank0 so no switching necessary
  bcf    PIR1,TMR1IF  ; clear Timer1 interrupt flag bit
  btfss  TmrFlag,0    ; has this timer expired?
  bra    DoTick2      ; yes, jump to Tick2
  incf  Tick1,F      ; no, increment Tick1 count           
  movf  Time1,W      ; get Time1                 
  subwf  Tick1,W         
  btfsc  STATUS,2    ; is Tick1 = Time1?     
  bra    Alarm1      ; yes, do alarm1
  bra    DoTick2      ; nope, not time, do Tick2 count
 
Alarm1
  bcf    Alarm,Out1  ; clear PORTD,0. turn off alarm1
  clrf  Tick1        ; clear Tick1 count, we're done
  bsf    State        ; indicate State change
  bcf    TmrFlag,0    ; expire Tick1. user has to re-arm by setting TmrFlag.0
 
DoTick2
  btfss  TmrFlag,1    ; has this timer expired?
  bra    ExitISR      ; yes, so exit
  incf  Tick2,F      ; no, increment Tick2 low byte count
  btfsc  STATUS,2    ; low byte over-flow?
  incf  Tick2+1,F    ; yes, increment Tick2 high byte
  movf  Time2+1,W    ; get Time2 high byte
  subwf  Tick2+1,W   
  btfsc  STATUS,2    ; are Time2 & Tick2 high bytes the same?
  bra    DoLow        ; yes, check low byte
  bra    ExitISR      ; no, exit
 
DoLow
  movf  Time2,W      ; get Time2 low byte
  subwf  Tick2,W
  btfsc  STATUS,2    ; are Time2 & Tick2 low bytes the same?
  bra    Alarm2      ; yes, do alarm2
  bra    ExitISR      ; nope, exit
KillTmr1
  bcf    T1CON,TMR1ON ; stop Timer1
  clrf  TMR1H        ; clear high/low counts
  clrf  TMR1L
  retfie              ; return with auto context restore
 
Alarm2
  bcf    Alarm,Out2  ; clear PORTD,1. turn off alarm2
  clrf  Tick2        ; clear Tick2 low
  clrf  Tick2+1      ; clear Tick2 high, we're done
  bsf    State        ; indicate State change
  bcf    TmrFlag,1    ; expire Tick2. user has to re-arm by setting TmrFlag.1
 
ExitISR
  movf  TmrFlag,W    ; load enable/disable flags
  sublw  0x00
  btfsc  STATUS,2    ; are both tick timers expired?
  bra    KillTmr1    ; yes, stop Timer1, we're done
  bcf    T1CON,TMR1ON ; no, still have one or more enabled, so stop Timer1
  movlw  0xb3        ; get low byte of reload value
  addwf  TMR1L,F      ; add to existing count
  btfsc  STATUS,2    ; low byte over-flow?
  incf  TMR1H,F      ; yes, bump-up TMR1 high byte by 1
  movlw  0x3c        ; no, get high byte to add
  addwf  TMR1H,F      ; add to existing TMR1 count for ~100mS interrupt intervals
  bsf    T1CON,TMR1ON ; re-start Timer1
  retfie              ; return with auto context restore
Endasm
 
' =============\ Main Program Start /============= ' 
Start:
  ' using IOCBF you can tap 1 or more keys very fast, and never miss
  ' a press. Much faster than reading the entire port. And key presses
  ' do not generate an interrupt. Only set flag bits in IOCBF for each
  ' individual input that was edge-triggered.
 
  If IocFlag Then    ' if keys SW13, 14, 15 or 16 were pressed,
      State = 1      ' indicate LCD update needed
      Gosub GetKeys  ' get the button/buttons pressed
  Endif
 
  If State Then      ' update status on LCD only after a change
      Gosub GetStatus ' in State
      State = 0
  Endif
 
  Goto Start        ' loop forever
 
' =============\ Update Output Status /============= '
GetStatus: 
  ' Print status of timed outputs
  If (PORTD.0 | TmrFlag.0) = 0 Then
      Lcdout $fe,2,"Out1 off  "
  Else
      Lcdout $fe,2,"Out1 on  "
  Endif
 
  If (PORTD.1 | TmrFlag.1) = 0 Then
      Lcdout $fe,$c0,"Out2 off  "
  Else
      Lcdout $fe,$c0,"Out2 on  "
  Endif
  Return
 
' ===========\ Get Keypad Switch Presses /=========== ' 
GetKeys:
  Pause 10              ' crude debounce for key press
 
  ' SW13 resets Out1
  If IOCBF.4 Then      ' IOCBF.4 = 1 when low edge detected on RB4
      While PORTB.4 = 0  ' wait for key release       
      Wend              '
      PORTD.0 = 1        ' activate output
      Tick1 = 0          ' reset Tick0 count
      TmrFlag.0 = 1      ' reset enable flag
      If !T1CON.0 Then T1CON.0 = 1 ' if Timer1 disabled, re-enable
  Endif
 
  ' SW14 resets Out2
  If IOCBF.5 Then      ' IOCBF.5 = 1 when low edge detected on RB5
      While PORTB.5 = 0  ' wait for key release
      Wend              '       
      PORTD.1 = 1        ' activate output
      Tick2 = 0          ' reset Tick2 count
      TmrFlag.1 = 1      ' reset enablg flag
      If !T1CON.0 Then T1CON.0 = 1 ' if Timer1 disabled, re-enable
  Endif
 
  ' SW15 disables Out1
  If IOCBF.6 Then      ' IOCBF.6 = 1 when low edge detected on RB6
      While PORTB.6 = 0  ' wait for key release
      Wend              '     
      TmrFlag.0 = 0      ' expire Out1 time immediately
      Tick1 = 0          ' reset Tick1 count
      PORTD.0 = 0        ' de-activate output
  Endif
 
  ' SW16 disables Out2
  If IOCBF.7 Then      ' IOCBF.7 = 1 when low edge detected on RB7
      While PORTB.7 = 0  ' wait for key release
      Wend              '       
      TmrFlag.1 = 0      ' expire Out2 time immediately
      Tick2 = 0          ' reset Tick2 count
      PORTD.1 = 0        ' de-activate output
  Endif
  IOCBF = 0            ' reset all int-on-change bits on exit
  IocFlag = 0
  Return
 
' ===========\ Hardware Initialization Routine /=========== ' 
Init:
  ANSELA = 0    ' porta all digital
  ANSELB = 0    ' portb all digital
  ANSELD = 0    ' portd all digital
  ANSELE = 0    ' porte all digital
 
  PORTD = %00000011  ' turn on alarm outputs
  TRISD = 0          ' PORTD all outputs
 
  OPTION_REG.7 = 0    ' enable PORTB pullups 
  PORTB = 0          ' RB3 low
  TRISB = %11110111  ' RB3 = 0 for output to keys 13, 14, 15, 16
  WPUB = %11110000    ' weak pull-ups on for ----> RB4, 5,  6,  7
  IOCBP = 0          ' positive edge disabled
  IOCBN = %11110000  ' negative edge int-on-change enabled for keys
  Pause 100          ' wait for LCD to start
  Lcdout $fe,1        ' clear LCD
 
  PIR1 = 0            ' clear interrupt flags before enabling interrupts below
  PIE1 = %00000001    ' Timer1 interrupt enabled
  INTCON = %11000000  ' global & peripheral interrupts enabled
 
  ' and finally -- setup & start Timer1
  TMR1L = $b3        ' load Timer1 for ~100mS over-flows
  TMR1H = $3c
  T1CON = %00010001  ' set 1:2 prescale, Timer1 on
  T1GCON = 0          ' Timer1 gate control not used
 
  Goto Start          ' start main program
 
  End

---