Strange problem with an 18F4580 based project

[malc-c]

Guy's, this is probably aimed at DT or Henrik as they are really familiar with my thermostat project, but I'm open to suggestions.

My prototype thermostat unit (details can be found at http://www.picbasic.co.uk/forum/showthread.php?t=12712) has been running now for around 6 months, but recently I've had two incidences where the unit appears to be running, but has actually locked up in some way, after I tried fixing a problem with a light that is driven from the unit.

The first instance the light was out, so whilst everything was still running I detached the cable and reseated the tube then plugged the light (an under cabinet florescent T5 tube) back in. Everything seemed OK until I noticed the snake in each vivarum move right up the cold end of the enclosure. The temperature on the LCD still showed 33.1C and both LEDs were pulsing away as normal, but on opening the viv the heat was obvious. I reset the controller and off went the alarms as both vivs were running at 45c (which was now shown on the display).

The second instance was the same, but this followed a simple tapping of the tube to get it to light. Only this time I noticed that the temperature readings from the DS18B20's didn't fluctuate (normally they are constantly changing every few seconds by +/- 0.1c).

It is as if the program in the chip stops running the PID loop or something but where you would expect the LCD to blank out, or the LEDs to stop pulsing if the chip stopped running that doesn't happen. Could it be the fuse settings? Can a PIC go into a state of limbo like this ??

I've been told that some of the commercial companies hang out on the reptile forums have got wind of my project so I don't really want to paste up the current version of the code in full, so PM me if you need the files. I can obviously post up spinets, if required.

Comments please

[Acetronics2]

Hi, Malc

@ First sight ... I could think the DS1820 do not update its scratchpad for any reason.
I read you use fluorescent tubes for lighting ... that rings my bell and I ask you

1) Which value for the pullup resistor ( usually 4.7k ... when sensor close to processor ! )
2) do you use ground shielded wire to connect your DSs ???
3) could you post me the DS identification and temp reading section of your program ? ( to see if any " health " control of the sensor is done )

may be we could think to some enforced DS chip " good running check " ...
some control like " heating power always rises, but temp not = default somewhere )

Alain

[malc-c]

Hi Alain, and thanks for posting.

Yes I'm using 4.7K resistors on each of the DS18B20's. The cable length is approx 2m from the tip of the sensor to the unit, and made up of three wires twisted (used a drill). My research didn't throw up anything about having to use shielded cable between the sensor and the PIC.

I'll zip up all the code (including the includes !) and let you check the code. To make things simpler, could you pm me your e-mail address.

Thanks

[malc-c]

Hope the following help

Initialization

;----[DS1820 Options]----Value----Default-----------------------------------
DEFINE  DS1820_DECIMALS    1                    ' 1
DEFINE  DS1820_VERIFYCRC   YES                  ' NO
DEFINE  DS18B20_ONLY       YES                  ' NO
INCLUDE "DT18x20.pbp"                           ' Include DT18x20 module

    FOR Bvar = 0 to 3                               ; assume all sensors are working
        SensorActive(Bvar) = 1
    NEXT Bvar
        
    FOR pid_Channel = 0 TO 3                        ; Set # of bits in resolution
        GOSUB SelectSensor                          ; for all sensors
        GIE = 0                                     ; disable interrupts before 1-wire
        @ DS1820_Resolution 12            
        GIE = 1                                     ; enable interrupts after 1-wire
    NEXT pid_Channel
        
    LOW HeaterOut1                                  ; set heater pins Output to off
    LOW HeaterOut2
    LOW HeaterOut3
    LOW HeaterOut4
    
    Low Lights1                                     ; set lighting pins to off
    Low Lights2

    GOSUB SendPWRstat

The subroutine referred to above

SendPWRstat:
    Bvar = 0
    Bvar.0 = ChannelPWR(0)
    Bvar.1 = ChannelPWR(1)
    Bvar.2 = ChannelPWR(2)
    Bvar.3 = ChannelPWR(3) 
RETURN

Now for the main part

    FOR pid_Channel = 0 TO 3                        ; cycle thru all sensors
        GOSUB SelectSensor
        DS1820_Error = 0                            ; clear any previous errors
        DS1820_Flags = 0                            ; clear status flags
        GIE = 0                                     ; disable interrupts before 1-wire
          @ DS1820_Stat                             ; check the sensors status
        GIE = 1                                     ; enable interrupts after 1-wire
        PAUSEUS 20
        IF !DS1820_Done THEN SensorError            ; if it's not done by now, error
        GIE = 0                                     ; disable interrupts before 1-wire
          @ DS1820_Read                             ; get the temperature result
        GIE = 1                                     ; enable interrupts after 1-wire
        GOSUB Check4Zeros
        
        DS1820_Flags = 0
        GIE = 0                                     ; disable interrupts before 1-wire
          @ DS1820_Stat
        GIE = 1                                     ; enable interrupts after 1-wire
        IF (DS1820_Error = 0) AND DS1820_Done THEN  ; if there were no errors
            Temperatures(pid_Channel) = TempC
            pid_Error = SetPoints(pid_Channel) - TempC
            GOSUB PID
            IF pid_Out.15 THEN pid_Out = 0          ; only keep positive values
            IF ChannelPWR(pid_Channel) THEN
                HeaterDrives(pid_Channel) = pid_Out
            ELSE
                HeaterDrives(pid_Channel) = 0
            ENDIF
IF Temperatures(pid_Channel) >  alarmhigh(pid_Channel) and Alarm = 1 then AlarmPin = 1
IF Temperatures(pid_Channel) >  alarmhigh(pid_Channel) and Alarm = 0 then AlarmPin = 0
IF Temperatures(pid_Channel) <=  alarmhigh(pid_Channel) then AlarmPin = 0
IF Temperatures(pid_Channel) <=  alarmlow(pid_Channel) then AlarmPin = 0
if Temperatures(pid_Channel) < alarmlow(pid_Channel)  and Alarm = 1 then AlarmPin = 1
if Temperatures(pid_Channel) < alarmlow(pid_Channel)  and Alarm = 0 then AlarmPin = 0
   
        GOSUB ShowLCD 
          
        ELSE
    SensorError:
           HeaterDrives(pid_Channel) = 0            ; turn off heater if sensor's bad
           SensorActive(pid_Channel) = 0
           GOSUB ShowError                          ; display error message
        ENDIF
    NEXT pid_Channel

The other two parts you may be interested in is the checking and displaying sections

AllZeros  VAR Bit
Check4Zeros:
    AllZeros = 1
    FOR Bvar = 0 TO 8
        IF DS1820_Buffer(Bvar) != 0 THEN AllZeros = 0
    NEXT Bvar
    IF AllZeros THEN DS1820_CRCfailed = 1
;------------------------------------------------------------------------------ 

;----[show output on LCD]------------------------------------------------------- 
ShowLCD:
    LOOKUP pid_Channel,[$80,$C0,$89,$C9],Bvar       ; Find location
    LCDOUT $FE,Bvar,DEC1 pid_Channel+1,"= "         ; print to LCD     
    TempWD = TempC : GOSUB TempToLCD                ; display TempC
    LCDOUT $DF                                      ; deg symbol

and the select sensor sub

SelectSensor:
  SELECT CASE pid_Channel
    CASE 0 : @ DS1820_Select  _TempSensor1      ; Select the DS18x20 pin
    CASE 1 : @ DS1820_Select  _TempSensor2
    CASE 2 : @ DS1820_Select  _TempSensor3
    CASE 3 : @ DS1820_Select  _TempSensor4
  END SELECT  
RETURN

If you need more drop me an e-mail or I can post up more snipets

[Darrel Taylor]

Malcolm,

The heater outputs are interrupt driven, so if the main program locks up somewhere due to an unexpected condition, the heaters will continue pulsing at the last drive level given from the PID loops.

I can't imagine all four DS18B20's having a problem at the same time. The program is checking CRC's.
If 1 VIV got hot and the others were OK, I might suspect a DS.

You may need to use the WDT to monitor the main loop.
Then it'll reset the processor if it gets lost.

Using ...
DEFINE NO_CLRWDT 1
PBP will not add CLRWDT instructions throughout the code.
Then "strategically" placing CLRWDT statements in your program will clear it as long as the loop is running.

I say strategically, because if you place a CLRWDT in the area where it's locking up, it won't help.

Since the problem seems to be repeatable by fiddling with the lights, it should be fairly easy to locate good placements of the CLRWDT statements.

Blinking an LED in the main loop may help identify when or if it's locked.

[malc-c]

Darrel,

Thanks for your input - with your prior knowledge of this project I thought you would be best placed to know what is going on.

OK I'll be perfectly honest, I'm not 100% sure where I would need to place the CLRWDT commands, so here is the main program loop

;-----------------------------------------------------------------------------
; *****  MAIN PROGRAMMING LOOP *****
;-----------------------------------------------------------------------------

Main:


If SetButton=0 then                                 ; jump to programming
Gosub SetButtonRelease
goto mainmenu
endif

If DecButton=0 then
Gosub SetButtonRelease
goto lightoveride                                   ; manual overide of light
endif

If IncButton=0 then
Gosub SetButtonRelease
goto cancelalarm                                   ; manual overide of alarm
endif


    FOR pid_Channel = 0 TO 3                        ; cycle thru all sensors
        GOSUB SelectSensor
        GIE = 0                                     ; disable interrupts before 1-wire
        @  DS1820_Convert                           ; start a temperature conversion
        GIE = 1                                     ; enable interrupts after 1-wire
    NEXT pid_Channel
     
;----[check for data on com port] 

    FOR TempWD = 0 TO 10000
        IF RCIF THEN GOto coms
        PauseUs 100
    NEXT TempWD
;--------------------------------    


    FOR pid_Channel = 0 TO 3                        ; cycle thru all sensors
        GOSUB SelectSensor
        DS1820_Error = 0                            ; clear any previous errors
        DS1820_Flags = 0                            ; clear status flags
        GIE = 0                                     ; disable interrupts before 1-wire
          @ DS1820_Stat                             ; check the sensors status
        GIE = 1                                     ; enable interrupts after 1-wire
        PAUSEUS 20
        IF !DS1820_Done THEN SensorError            ; if it's not done by now, error
        GIE = 0                                     ; disable interrupts before 1-wire
          @ DS1820_Read                             ; get the temperature result
        GIE = 1                                     ; enable interrupts after 1-wire
        GOSUB Check4Zeros
        
        DS1820_Flags = 0
        GIE = 0                                     ; disable interrupts before 1-wire
          @ DS1820_Stat
        GIE = 1                                     ; enable interrupts after 1-wire
        IF (DS1820_Error = 0) AND DS1820_Done THEN  ; if there were no errors
            Temperatures(pid_Channel) = TempC
            pid_Error = SetPoints(pid_Channel) - TempC
            GOSUB PID
            IF pid_Out.15 THEN pid_Out = 0          ; only keep positive values
            IF ChannelPWR(pid_Channel) THEN
                HeaterDrives(pid_Channel) = pid_Out
            ELSE
                HeaterDrives(pid_Channel) = 0
            ENDIF
IF Temperatures(pid_Channel) >  alarmhigh(pid_Channel) and Alarm = 1 then AlarmPin = 1
IF Temperatures(pid_Channel) >  alarmhigh(pid_Channel) and Alarm = 0 then AlarmPin = 0
IF Temperatures(pid_Channel) <=  alarmhigh(pid_Channel) then AlarmPin = 0
IF Temperatures(pid_Channel) <=  alarmlow(pid_Channel) then AlarmPin = 0
if Temperatures(pid_Channel) < alarmlow(pid_Channel)  and Alarm = 1 then AlarmPin = 1
if Temperatures(pid_Channel) < alarmlow(pid_Channel)  and Alarm = 0 then AlarmPin = 0
   
        GOSUB ShowLCD 
          
        ELSE
    SensorError:
           HeaterDrives(pid_Channel) = 0            ; turn off heater if sensor's bad
           SensorActive(pid_Channel) = 0
           GOSUB ShowError                          ; display error message
        ENDIF
    NEXT pid_Channel

     
;   ---------------------------------------------------------------------------
;   check lighting periods and turn lights on or off accordingly
;   ---------------------------------------------------------------------------

    fn = 0                                                      ; select the first Lights
    if lightover = 0 then GOSUB CheckTimes                      ; if manual override set to off then go compare the programed period
    if lightover = 1 then progON=1                              ; if manual override flag set to on then lights on flag set to 1
    IF ProgON THEN                                              ; If in the program period
       IF Lights1 = 0 THEN Lights1 = 1
    ELSE
       IF Lights1 = 1 THEN Lights1 = 0
       IF Lights1 = 0 then LCDOut $FE, $94+9,"          " 
    ENDIF

    fn = 1                                                      ; select the second Lights
    if lightover = 0 then GOSUB CheckTimes                      ; compare the programed period
    IF ProgON THEN
        IF Lights2 = 0 THEN Lights2 = 1

    ELSE
        IF Lights2 = 1 THEN Lights2 = 0
     LCDOut $FE, $94+9,"          "
     ENDIF
    IF Lights1 = 1 then LCDOut $FE, $94+9,"Light 1 ON"
    IF Lights2 = 1 then LCDOut $FE, $94+9,"Light 2 ON"   
    if Lights1 = 1 and Lights2 = 1 then LCDOut $FE, $94+9,"Lights ON "
    If Lights1 = 0 and Lights2 = 0 then LCDOut $FE, $94+9,"          "

     
;   ---------------------------------------------------------------------------
;   Check for night time drops - if condition matched, drop temp
;   ---------------------------------------------------------------------------

    fn = 0                            ; select the first setting
    GOSUB CheckTimes2                   ; compare the programed period
    IF ProgON2 THEN
    SetPoints[0]=Droptemp[0]          ; change the corresponding set point to the drop temperature
    LCDOut $FE, $94,"Night"
    ELSE
    SetPoints[0]= normtemp[0]          ; change the corresponding drop temperature to set point
    LCDOut $FE, $94,"     "
    ENDIF    
  
    fn = 1                              ; select the second setting
    GOSUB CheckTimes2                   ; compare the programed period
    IF ProgON2 THEN
    SetPoints[1]=Droptemp[1]          ; change the corresponding set point to the drop temperature
    LCDOut $FE, $94,"Night"
    ELSE
    SetPoints[1]= normtemp[1]          ; change the corresponding drop temperature to set point
    LCDOut $FE, $94,"     "
    ENDIF  
     
    fn = 2                              ; select the third setting
    GOSUB CheckTimes2                   ; compare the programed period
    IF ProgON2 THEN
    SetPoints[2]=Droptemp[2]          ; change the corresponding set point to the drop temperature
    LCDOut $FE, $94,"Night"
    ELSE
    SetPoints[2]= normtemp[2]          ; change the corresponding drop temperature to set point
    LCDOut $FE, $94,"     "
    ENDIF  
     
    fn = 3                              ; select the fouth setting
    GOSUB CheckTimes2                   ; compare the programed period
    IF ProgON2 THEN
    SetPoints[3]=Droptemp[3]          ; change the corresponding set point to the drop temperature
    LCDOut $FE, $94,"Night"
    ELSE
    Setpoints[3]= normtemp[3]          ; change the corresponding drop temperature to set point
    LCDOut $FE, $94,"     "
    ENDIF   
     
     
     
;----[Flash Star on LCD]-------------------------------------------------------              
If alarm=1 then
    LCDOUT $FE,$80 + 18,("*"&FlashStar*$FF)|(" "&~(FlashStar*$FF)) ; flash a star to show sample time, but used to indicate Alarm settings monitored
    FlashStar = !FlashStar 
endif                             




;-----------------------------------------------------------------------------
; *****  MAIN PROGRAMMING LOOP END *****
GOTO Main                                
;-----------------------------------------------------------------------------

Could you advise me ??

Thanks