Elapsed timer not working as expected at 64MHz

[richard]

debug T1PS and TimerConst to see what's going on would be a good start

[Demon]

Roger, oveur.

[longpole001]

yep there was no elapsed-18_k22

[richard]

seems to me the easiest way to restore correct function for "ticks" when the post scaler is in use is to move the ticks loop inside the post scale loop , no extra vars no extra overhead

ClockCount:
@ RELOAD_TIMER                   ; Reload TIMER1

    T1Post = T1Post + 1
    IF T1Post = T1PS THEN
      T1Post = 0
     Ticks = Ticks + 1
        IF Ticks = 100 THEN
           Ticks = 0
           Seconds = Seconds + 1
           SecondsChanged = 1
           IF Seconds = 60 THEN
              Seconds = 0
              Minutes = Minutes + 1
              MinutesChanged = 1
           ENDIF
           IF Minutes = 60 THEN
              Minutes = 0
              Hours = Hours + 1
              HoursChanged = 1
           ENDIF
           IF Hours = 24 THEN
              Days = Days + 1
              DaysChanged = 1
              Hours = 0
           ENDIF
       ENDIF
    ENDIF
@ INT_RETURN                     ; Restore context and return from interrupt

[Demon]

I can only think that there was a reason why Darrel did it as he did. The dude could probably code this stuff while playing ping pong; the Bruce Lee of PBP and ASM.

There's more than one way to solve a problem, he probably took the one that worked for all PICs (until the K22 series came along). And even that he's solved the problem, it just wasn't widely known. I can only think he had greater concerns on his mind. Can you imagine how much of a headache it must have been tracking the new releases versus his routines? Makes me appreciate and miss him even more.

I now fear the day when Microchip releases a new product line. I love the K22 like I loved the 16F628 and 16F877, I'm not changing unless I'm forced to change.

Shoot, I might even stay on PBP 2.6. LOL

[richard]

it has nothing to do with the k22's its the problem exists whenever the T1PS value is >1 on any chip
its all to do with the way he implemented the post scaling , the loops are inside out . its no bigie to fix . its only apparent if you need to use "ticks" .
imho most of the time using ticks is pointless by the time you process the reading and then display it it's already meaningless and out of date . if you want to time events to such accuracy trigger times need to be allowed for and properly sync'ed , there are much better ways
ps
the k22 interrupt vagaries are a separate issue and unrelated to ticks not being 100th's of a sec

[Demon]

its only apparent if you understand what's going on .

There, fixed it for you. LOL

I never dealt with timer guts before. I always thought pre-scaling and post-scaling were what the fish looked like when my mom prepared them.

Oh and I don't like fish.

Robert

[richard]

you have to toggle your led at the correct place in the loop
the interrupt runs at 4x the speed required (because of high fosc not chip type ) for timing so the post scaler divides it by 4

ClockCount:
@ RELOAD_TIMER ; Reload TIMER1

T1Post = T1Post + 1
Robert toggle your pin here eg latd.0=!latd.0 for 2.5mS
IF T1Post = T1PS THEN
T1Post = 0
Ticks = Ticks + 1
Robert toggle your pin here eg latd.1=!latd.1 for 10mS
IF Ticks = 100 THEN
Ticks = 0
Seconds = Seconds + 1
SecondsChanged = 1
IF Seconds = 60 THEN
Seconds = 0
Minutes = Minutes + 1
MinutesChanged = 1
ENDIF
IF Minutes = 60 THEN
Minutes = 0
Hours = Hours + 1
HoursChanged = 1
ENDIF
IF Hours = 24 THEN
Days = Days + 1
DaysChanged = 1
Hours = 0
ENDIF
ENDIF
ENDIF
@ INT_RETURN ; Restore context and return from interrupt

[Demon]

...imho most of the time using ticks is pointless by the time you process the reading and then display it it's already meaningless and out of date . if you want to time events to such accuracy trigger times need to be allowed for and properly sync'ed , there are much better ways
ps
the k22 interrupt vagaries are a separate issue and unrelated to ticks not being 100th's of a sec

I disagree. This is the first time I have a specialized need for a timer and it requires knowing how long a tick really is. I want to debounce using interrupts, so I press a button, look how long it takes for the contact to close and open again, take an arbitrary average and add maybe 25%, that's my debounce in mSeconds.

I know others use timers in what I consider a more complicated way, I have no clue how a preload value works and can never remember if the timer counts up or down from there (I have a hard time remembering little details like that). To them it's easier, I prefer the elapsed timer approach.

I turn a LED on and off, check the interval on the Saleae probe (I should get a commission every time I typed that), and that's it. Ticks=10mS is stuck in my brain ever since I first saw it on Darrel's include. I just count the ticks until I get my interval.

When you think about it, if we were that concerned with accuracy, we'd program in assembler.

Robert

[Demon]

debug T1PS and TimerConst to see what's going on would be a good start

I started by making my version of the Elapsed include and adding 2 variables at the end of the timer calc:

...
' -------------- calc timer reload Constants -------------------------------
ASM
T1PS = 1                             ; start with 1:1 postscaler
TimerConst = ((OSC*1000000)/4/100)   ; how many timer ticks will it take
  while TimerConst > 65400           ; if it's more than the timer can count
T1PS = T1PS * 2                      ;   double the postscaler
TimerConst = TimerConst / 2          ;   halve the count
  endw
TimerConst = 65536 - TimerConst + 8  ; final reload value
; ---------------------------- DEBUG SCALER --------------------------------
DebugT1PS = T1PS
DebugTC = TimerConst
; xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
...

Before Main of my program I added:

DebugT1PS CON EXT
DebugTC   CON EXT

Right now I'm wiring up a LCD to display the 2 variables.

Am I on the right track to look at them?

I've never tried to display something from inside Darryl's includes before. My plan was to copy them into 2 words and then displaying the lower and upper bytes on the LCD.

[richard]

Am I on the right track to look at them?

probably not if yours fails try this

DISABLE DEBUG

; syntax =     Handler  IntSource,        Label, Type, ResetFlag?
DEFINE  Elapsed_Handler  TMR1_INT,  _ClockCount,  asm,  yes
; the above define can be used in the INT_LIST macro, if desired (optional)

Ticks            VAR BYTE   ; Counts timer Overflows
T1Post           VAR BYTE   ; Timer1 postscaler
Seconds          VAR BYTE
Minutes          VAR BYTE
Hours            VAR BYTE
Days             VAR WORD
DebugT1PS     var byte
DebugTCL       var byte 
DebugTCh       var byte 

SecondsChanged   VAR BIT    ; idicates that the value has changed
MinutesChanged   VAR BIT
HoursChanged     VAR BIT
DaysChanged      VAR BIT

GOSUB ResetTime             ; initialize the Elapsed Timer

Goto OverElapsed            ; skip over the routines

' -------------- calc timer reload Constants -------------------------------
ASM
T1PS = 1                             ; start with 1:1 postscaler
TimerConst = ((OSC*1000000)/4/100)   ; how many timer ticks will it take
  while TimerConst > 65400           ; if it's more than the timer can count
T1PS = T1PS * 2                      ;   double the postscaler
TimerConst = TimerConst / 2          ;   halve the count
  endw
TimerConst = 65536 - TimerConst + 8  ; final reload value
 _DebugT1PS =T1PS
 _DebugTCH=TimerConst /256 
 _DebugTCL = TimerConst - _DebugTCH*256

; -----------------  ADD TimerConst to TMR1H:TMR1L -------------------------
ADD2_TIMER   macro

[Demon]

Actually, it worked.

I deleted my debug include 'cause I can work without it.

...
;T1PS        CON EXT    ' Already defined in include
TimerConst  CON EXT

varT1PS   var word
varTC     var word
    varT1PS = T1PS
    varTC   = TimerConst
    
    Lcdout $fe, 1, "Timer 1"
    Lcdout $fe, $94, "PS:", BIN8 varT1PS.byte1, " ", BIN8 varT1PS.byte0
    Lcdout $fe, $D4, "TC:", BIN8 varTC.byte1, " ", BIN8 varTC.byte0

MainProgram:

And I get:
PS:00000000 00000001
TC:01100011 11001000 <--- Dec=25544

EDIT: Woooops, still using OSC 16, BRB.

[Demon]

OSC 64 (16 + PLL)

PS:00000000 00000100 <--- Dec=4
TC:01100011 11001000 <--- Dec=25544

I had same results manually this afternoon.

Robert

[richard]

ok next whats in T1CON ?

[Demon]

Looking at the datasheet for 18F44K22, timer 1 has a 2 bit prescaler.

4 (100) takes 3 bits.

Gonna try timer 2.

...
13.0 TIMER2/4/6 MODULE p.175
...
• 8-bit Timer and Period registers (TMRx and PRx,
respectively)
• Readable and writable (both registers)
• Software programmable prescaler (1:1, 1:4, 1:16)
• Software programmable postscaler (1:1 to 1:16)
...

EDIT: Darn, DT Elapsed include only has Timer1...

Robert

[Demon]

Was looking at T1CON register and noticed this:

TxCKPS<1:0>: Timer1/3/5 Input Clock Prescale Select bits
11 = 1:8 Prescale value
10 = 1:4 Prescale value
01 = 1:2 Prescale value
00 = 1:1 Prescale value

So that is 2 bits.

bit 7-6 TMRxCS<1:0>: Timer1/3/5 Clock Source Select bits
  11 =Reserved. Do not use.
  10 =Timer1/3/5 clock source is pin or oscillator:
    If TxSOSCEN = 0:
      External clock from TxCKI pin (on the rising edge)
    If TxSOSCEN = 1:
      Crystal oscillator on SOSCI/SOSCO pins
  01 =Timer1/3/5 clock source is system clock (FOSC)
  00 =Timer1/3/5 clock source is instruction clock (FOSC/4)

bit 5-4 TxCKPS<1:0>: Timer1/3/5 Input Clock Prescale Select bits
  11 = 1:8 Prescale value
  10 = 1:4 Prescale value
  01 = 1:2 Prescale value
  00 = 1:1 Prescale value

bit 3 TxSOSCEN: Secondary Oscillator Enable Control bit
  1 = Dedicated Secondary oscillator circuit enabled
  0 = Dedicated Secondary oscillator circuit disabled

bit 2 TxSYNC: Timer1/3/5 External Clock Input Synchronization Control bit
    TMRxCS<1:0> = 1X
  1 = Do not synchronize external clock input
  0 = Synchronize external clock input with system clock (FOSC)
    TMRxCS<1:0> = 0X
  This bit is ignored. Timer1/3/5 uses the internal clock when TMRxCS<1:0> = 1X.

bit 1 TxRD16: 16-Bit Read/Write Mode Enable bit
  1 = Enables register read/write of Timer1/3/5 in one 16-bit operation
  0 = Enables register read/write of Timer1/3/5 in two 8-bit operation

bit 0 TMRxON: Timer1/3/5 On bit
  1 = Enables Timer1/3/5
  0 = Stops Timer1/3/5
    Clears Timer1/3/5 Gate flip-flop

T1CON=00000000

Robert

[richard]

ITS NOT using the prescaler those bits need to be 00 ie 1:1
@64mhz with a preload of 25544 you get a tmr1 int every 2.5mS dt's int routine inc's the tips counter till its 4 then inc's the elapsed time clock I count ie once every 10mS

next step after confirming t1con is ok is to toggle a pin in the int routine as per what Sheldon suggested and verify 2.5mS ints are occurring

[Demon]

In the Elapsed include:

...
' -------------- calc timer reload Constants -------------------------------
ASM
T1PS = 1                             ; start with 1:1 postscaler
TimerConst = ((OSC*1000000)/4/100)   ; how many timer ticks will it take
  while TimerConst > 65400           ; if it's more than the timer can count
T1PS = T1PS * 2                      ;   double the postscaler
TimerConst = TimerConst / 2          ;   halve the count
  endw
TimerConst = 65536 - TimerConst + 8  ; final reload value
...

Darryl talks about a post-scaler. Timers 1, 3 and 5 have none for a 18F44K22?

Neither does Timer 0, only Timers 2,4 and 6 have pre and post-scalers.

Robert

[richard]

t1con looks good should be 0 or 1 (on or off) depending on what the int routine is up to