Altering a variable in a loop.

[jmgelba]

Ok I programmed and there are a couple of issues.

There needs to be a time delay between each step up or down that the button is pressed. Right now, pressing either button and it is too fast to set a desired level. This delay cant be put into the loop though as the response of the regulator will be to slow.

Also it doesnt fully turn off and seems to settle at a very low duty cycle when it should be zero.

IF but_0 then
pause 75
eNDIF
if !but_0 then
         if SETPOINT>0 then
            SETPOINT=SETPOINT-1
           endif
           
    endif
    
IF but_1 then
PAUSE 75
ENDIF    
    if !but_1 then
            if SETPOINT<19 then
            SETPOINT=SETPOINT+1
        endif
        
    endif

This button code used before worked well.

[jmgelba]

 If UpButton THEN
    PAUSE 75
    Setting = Setting + 1              ' Increment setting
    If Setting = 6 THEN Setting = 5    ' Make sure it doesn't go beyond 5
    SettingChanged = 1                 ' Set flag indicating new setting
  EndIf


  If DnButton THEN
    PAUSE 75
    Setting = Setting - 1
    If Setting = 255 THEN Setting = 0  ' Make sure it doesn't go below 0
    SettingChanged = 1                 ' Set flag indicating new setting
  EndIf

Adding the PAUSE 75 fixed the run away issue and gives a quick response to a button press while still being easy to use.

Still havent figured out why at DutyCycle=0 there is still a very low pwm signal that lasts for just a few uS. Or while at setting 5 it rolls over to setting 1.

[HenrikOlsson]

There's a mistake in my code.
The Setting variable can go from 0 to 5 (6 settings) but there's only five entries in the first LOOKUP statement, the one that sets the initial dutycycle.

[jmgelba]

I did actually catch that And yes, it does work. Or it did. Now I think I either messed it up or there is a hardware issue

[jmgelba]

Define OSC 20
DEFINE ADC_BITS 10
DEFINE ADC_CLOCK 3
DEFINE ADC_SAMPLEUS 50
DEFINE CCP1_REG PORTB
DEFINE CCP1_BIT 3


PORTA = %00000000       ' Turn off all PORTA 
PORTB = %00000000       ' Turn off all PORTB
ADCON0 = %00000001
ADCON1 = %01111000
ADCON2 = %10000111

TRISA = %11100111
TRISB = %11000011


UpButton VAR PortB.0   			' Active high button
DnButton VAR PortB.1   			' Active high button

Setting VAR BYTE
SettingChanged VAR BIT
DutyCycle VAR WORD
SETPOINT var byte  'Output current level in 0.1A increments)100 = 1A)

CURRENT VAR WORD
LEDCURRENT VAR WORD
LEDCURRENT1 VAR WORD
high_duty var word
low_duty var word



Main:

  If UpButton THEN
  pause 75
    Setting = Setting + 1              ' Increment setting
    If Setting = 6 THEN Setting = 5    ' Make sure it doesn't go beyond 5
    SettingChanged = 1                 ' Set flag indicating new setting
  EndIf


  If DnButton THEN
  pause 75
    Setting = Setting - 1
    If Setting = 255 THEN Setting = 0  ' Make sure it doesn't go below 0
    SettingChanged = 1                 ' Set flag indicating new setting
  EndIf

  If SettingChanged THEN
    LOOKUP Setting, [0,100,150,200,240,254], DutyCycle
    LOOKUP Setting, [0, 2, 5, 9, 14, 17], SetPoint ' Assign value to setpoint variable 
    SettingChanged = 0                 ' Clear flag
  EndIf
  
ADCIN 0, CURRENT
LEDCURRENT = CURRENT * 49 /100 *2
LEDCURRENT1 = LEDCURRENT/10

CCP1CON = %00111100
PR2 = 99
high_duty=(dutycycle>>2)        'high 6 bits in CCPR1L
      low_duty=(dutycycle<<6)         'low two bits for CCP1CON
      'low_duty=(low_duty>>2)           'shift back to CCP1CON<5:4>
      low_duty.4=0                     'PWM configuration bit
      low_duty.5=1                     'PWM configuration bit
CCPR1L=high_duty
CCP1CON = $0C
T2CON = 4

if LEDCURRENT1 < setpoint then
    dutycycle=dutycycle+1
    if dutycycle => 300 then
    dutycycle = 300
endif
ENDIF
if LEDCURRENT1 > setpoint then
    dutycycle=dutycycle-1
    IF dutycycle > 301 then
    dutycycle = 0
    
ENDIF
endif
pause 100
Goto Main

Ok seem to be stuck. It no longer responds to button presses, turns off the LED if I raise the input voltage to 22V - should operate from 19 - 42V, and the pwm output is a constant low %. I have no idea what is causing this.

The pause 100 at the end is just to slow things down so I can see whats happening on the scope.

[jmgelba]

At the start of the program before the loop, I made sure Setting = 0. Works very well now. Still a minor issue of the pwm signal never turning off though, even on a setting of 0.

[HenrikOlsson]

Hi,
I think the problem is here:

CCP1CON = %00111100            '<-- Here you actually set the two LSB's of the dutycycle register.
PR2 = 99                                  ' <--There's no need to set PR2 every time thru the loop.
high_duty=(dutycycle>>2)        'high 6 bits in CCPR1L
      low_duty=(dutycycle<<6)         'low two bits for CCP1CON 
      'low_duty=(low_duty>>2)           'shift back to CCP1CON<5:4>  
      low_duty.4=0                     'PWM configuration bit 
      low_duty.5=1                     'PWM configuration bit
CCPR1L=high_duty
CCP1CON = $0C                       '<- Then you reset the two LSB's of the dutycycle register.
T2CON = 4                               '<- No need to set this every time

So, the glitch probably comes from the fact that even when your dutycycle variable is 0 you actually set the dutycycle to 4 (the two LSBs in CCP1CON being set by CCP1CON = %00111100) and then back to 0 again by CCP1CON = $0C.

Set up the module (ie CCP1CON and PR2) at the beginning of the program. If you need to use the lower two LSBs of the dutycycle then assign those bits in CCP1CON individually each time thru the loop. Don't mess with PR2 or T2CON every time thru the loop.

Finally, you do a lot of bit shifting an dflippin on the Low_Duty variable but you never actually USE it to set the dutycycle, you're only using the 8 high bits in CCPR1L.

/Henrik.