setting values and percentages

[Scampy]

Hi,

I'm in the process of developing my LED Aquarium light controller a stage further and smoothing out the pulse width modulation by using 0 - 4095 steps rather than the current 255 setps. I have the leds fading nicely when using preset hard coded values, but I want to be able to program the maximum setting for brightness via the LCD as a percentage between 0 and 100 %. When I used 255 steps the following code worked

brightness:
 
Lcdout $FE,2
LCDOUT $FE,$80,"Set Max Brightness"
IF H_butt = 0 THEN GOSUB up
IF M_butt = 0 THEN GOSUB down
If (maxbright * 100)/255 = 100 then
LCDOUT $FE,$C0,"Channel 1 "
LCDOut $FE,$D4,dec3 (maxbright *100)/255,"%"
endif

If (maxbright * 100)/255 =0 or (maxbright * 100)/255 <10 then
LCDOUT$FE,$C0,"Channel 1 "
LCDOut $FE,$D4,dec1 (maxbright *100)/255,"% "
endif

if (maxbright * 100)/255 >=10 and (maxbright * 100)/255 <100 then
LCDOUT$FE,$C0,"Channel 1 "
LCDOut $FE,$D4,dec2 (maxbright *100)/255,"%   "
endif
    B_max = maxbright 
write 8,b_max      
    
If S_butt = 0 then
    pause 200 
    goto brightness2
endif 
goto brightness

But I'm stumped trying to convert this to use 4095 steps. Replacing the 255 with 4095 seemed the logical answer, but that didn't work. Changing the < = or > values (ie 10% would be 409.5) didn't work either.

Any suggestions ?

[richard]

you will find that the led 'brightness' will not be a linear progression over the full 4096 steps anyway . its probably easier to have a finite number of brightness levels in a lookup table (how many brightness levels do you think the average person could differentiate between?)
try starting with 20 levels [ 0=off ,( and 18 between ) , 4095=full on] , those in between levels could be established by observation

[Demon]

Wouldn't he be better just staying with 255? Or am I missing something obvious?

Robert

[richard]

maybe malcom could refresh us on the issue , but as I understand it
1.the external pwm chip has 4096 steps
2.the loop update time is in 1 sec intervals
3. the desired fade in /out period divided by the loop time yields too few "pwm" steps for a smooth looking transition if you simply divide 4096 by the number of available steps

my theory is that if the steps are chosen well the effect may be smoother

[Scampy]

maybe malcom could refresh us on the issue , but as I understand it
1.the external pwm chip has 4096 steps
2.the loop update time is in 1 sec intervals
3. the desired fade in /out period divided by the loop time yields too few "pwm" steps for a smooth looking transition if you simply divide 4096 by the number of available steps

my theory is that if the steps are chosen well the effect may be smoother

Close

With a friends help I've implemented a routine using the internal timers to get timings under a second.

ASM
INT_LIST  macro   ;  IntSource,   Label,        Type, ResetFlag?
        INT_Handler   TMR1_INT,  _ToggleLED1,   ASM,  yes        
    endm
    INT_CREATE                                  ; Creates the interrupt processor
ENDASM

T1CON = %00000001                               ; free-running, 1:1 prescaler
TMR1H = %11111111
TMR1L = %11111011
@   INT_ENABLE   TMR1_INT                       ; enable Timer1 interrupts

And

ToggleLED1:
TMR1H = %11111111
TMR1L = %11111011
pcaPwmValue0=pcaPwmValue0+1 
pcaPwmValue1=pcaPwmValue1+1 
@ INT_RETURN

I can go from 0 - 4095 in less than two minutes, which helps in test runs.

The ramp up is controlled by the case statement

case DAWN
lcdout $FE,$80+15,"DAWN "  
if pcaPwmValue0 => blue_delay_in then 
B_PWM=B_PWM+1
pcaPwmValue0 = 0 
endif
if B_PWM => B_MAX then   
Blue_Day_Cycle = DAY
endif

The value for the pulse width is then written to the PCA chip in the main loop

pcaChannel = 0                                              ;Set a PWM channel
lcdout $FE,$80,"CH1"
i2cControl = $6 + 4*pcaChannel                              ;LED0_ON_L $6
I2CWRITE SDApin,SCLpin,i2cWriteAddress,i2cControl,[0,0,0,B_PWM ]

I have everything working fine, when using pre-set values for the fade in times and brightness and can do a full dawn, day, dusk, night cycle in five minutes, I just need to be able to sort out the manual settings for adjusting the the brightness so I can enter 0-100% rather than 0 - 4095 on the LCD

Hope this additional information helps

[HenrikOlsson]

How about

PWMValue = Percentage */ 10483

?

[Scampy]

Bit of a fudge, but it works well enough

'*******************************************************************************
' Set Brightness levels for each channel


brightness:

B_max = (4095/100)*maxbright

Lcdout $FE,2
LCDOUT $FE,$80,"Set Max Brightness"
IF H_butt = 0 THEN GOSUB up
IF M_butt = 0 THEN GOSUB down

If maxbright  = 100 then
LCDOUT $FE,$C0,"Channel 1 "
LCDOut $FE,$D4,#maxbright,"%"
endif

If maxbright  =0 or maxbright <10 then
LCDOUT$FE,$C0,"Channel 1 "
LCDOut $FE,$D4,dec1 maxbright,"% "
endif

if maxbright >=10 and maxbright <100 then
LCDOUT$FE,$C0,"Channel 1 "
LCDOut $FE,$D4,dec2 maxbright,"%   "
endif
     
If S_butt = 0 then
    pause 100 
    goto brightness2
endif 
goto brightness



brightness2: 
 
W_max = (4095/100)*maxbright

Lcdout $FE,2
LCDOUT $FE,$80,"Set Max Brightness"
IF H_butt = 0 THEN GOSUB up
IF M_butt = 0 THEN GOSUB down

If maxbright  = 100 then
LCDOUT $FE,$C0,"Channel 2 "
LCDOut $FE,$D4,#maxbright,"%"
endif

If maxbright  =0 or maxbright <10 then
LCDOUT$FE,$C0,"Channel 2 "
LCDOut $FE,$D4,dec1 maxbright,"% "
endif

if maxbright >=10 and maxbright <100 then
LCDOUT$FE,$C0,"Channel 2 "
LCDOut $FE,$D4,dec2 maxbright,"%   "
endif

pause 200
If S_butt = 0 then
    pause 100 
    LCDOUT $FE,1   
    goto mainmenu
endif
goto brightness2

up:
    maxbright = maxbright + 1
    IF maxbright >= 100 THEN maxbright = 100
    pause 250
RETURN
down:
    maxbright = maxbright - 1
    IF maxbright <= 0 THEN maxbright = 0
    pause 250
RETURN

Again, the lack of floating point maths in PBP means the calculations are not exact, but this way every 1% increment equals a block of 41 steps on the PCA chip, so 50% brightness = 2050 but that's close enough to the 2047 is should be and to be honest I doubt if the human eye could distinguish the difference

[HenrikOlsson]

Hi,
If it works it works.
If you want it a little better PWMValue = Percentage */ 10483 will give you 2047 at 50%.

/Henrik.

[EarlyBird2]

Hi,

I'm in the process of developing my LED Aquarium light controller a stage further and smoothing out the pulse width modulation by using 0 - 4095 steps rather than the current 255 setps. I have the leds fading nicely when using preset hard coded values, but I want to be able to program the maximum setting for brightness via the LCD as a percentage between 0 and 100 %. When I used 255 steps the following code worked

brightness:
 
Lcdout $FE,2
LCDOUT $FE,$80,"Set Max Brightness"
IF H_butt = 0 THEN GOSUB up
IF M_butt = 0 THEN GOSUB down
If (maxbright * 100)/255 = 100 then
LCDOUT $FE,$C0,"Channel 1 "
LCDOut $FE,$D4,dec3 (maxbright *100)/255,"%"
endif

If (maxbright * 100)/255 =0 or (maxbright * 100)/255 <10 then
LCDOUT$FE,$C0,"Channel 1 "
LCDOut $FE,$D4,dec1 (maxbright *100)/255,"% "
endif

if (maxbright * 100)/255 >=10 and (maxbright * 100)/255 <100 then
LCDOUT$FE,$C0,"Channel 1 "
LCDOut $FE,$D4,dec2 (maxbright *100)/255,"%   "
endif
    B_max = maxbright 
write 8,b_max      
    
If S_butt = 0 then
    pause 200 
    goto brightness2
endif 
goto brightness

But I'm stumped trying to convert this to use 4095 steps. Replacing the 255 with 4095 seemed the logical answer, but that didn't work. Changing the < = or > values (ie 10% would be 409.5) didn't work either.

Any suggestions ?

This code displays the maxbright value which comes from the up/down routines could you post these? Also obviously maxbright has to be a word?

[richard]

just notice your brackets are still incorrect too . if you use multiple logical conditions in if statements they must be parenthesized
eg
If (maxbright * 100)/255 =0 or (maxbright * 100)/255 <10 then

should be

If ((maxbright * 100/255 =0 ) or ( (maxbright * 100/255 <10 ) then

[EarlyBird2]

When I used 255 steps the following code worked

Richard,

I am puzzled because like you I believe the parenthesis are required but in this case apparently not. Certainly they are for other software and therefore I use them as you do as "good practice".

[richard]

with out the brackets you rely on the "operator precedence" order that the compiler will use , its often not what you really want . best bet is to always use brackets it eliminates the doubt

ps I typed reply #6 wrong left the closing brackets after 100's out
should be
If ((maxbright * 100)/255 =0 ) or ( (maxbright * 100)/255 <10 ) then

[Scampy]

Hi Guys and thanks for the input.

As requested here is the complete brightness routine that works when using Darrels software PWM.

brightness:
 
Lcdout $FE,2
LCDOUT $FE,$80,"Set Max Brightness"
IF H_butt = 0 THEN GOSUB up
IF M_butt = 0 THEN GOSUB down
If (maxbright * 100)/255 = 100 then
LCDOUT $FE,$C0,"Channel 1 "
LCDOut $FE,$D4,dec3 (maxbright *100)/255,"%"
endif

If (maxbright * 100)/255 =0 or (maxbright * 100)/255 <10 then
LCDOUT$FE,$C0,"Channel 1 "
LCDOut $FE,$D4,dec1 (maxbright *100)/255,"% "
endif

if (maxbright * 100)/255 >=10 and (maxbright * 100)/255 <100 then
LCDOUT$FE,$C0,"Channel 1 "
LCDOut $FE,$D4,dec2 (maxbright *100)/255,"%   "
endif
    B_max = maxbright 
write 8,b_max      
    
If S_butt = 0 then
    pause 200 
    goto brightness2
endif 
goto brightness

brightness2: 
 
Lcdout $FE,2
LCDOUT $FE,$80,"Set Max Brightness"
IF H_butt = 0 THEN GOSUB up
IF M_butt = 0 THEN GOSUB down
If (maxbright * 100)/255 = 100 then
LCDOUT $FE,$C0,"Channel 2 "
LCDOut $FE,$D4,dec3 (maxbright *100)/255,"%"
endif

If (maxbright * 100)/255 =0 or (maxbright * 100)/255 <10 then
LCDOUT$FE,$C0,"Channel 2 "
LCDOut $FE,$D4,dec1 (maxbright *100)/255,"% "
endif

if (maxbright * 100)/255 >=10 and (maxbright * 100)/255 <100 then
LCDOUT$FE,$C0,"Channel 2 "
LCDOut $FE,$D4,dec2 (maxbright *100)/255,"%   "
endif
    
    W_max = maxbright
write 9,W_max 
pause 200
If S_butt = 0 then
    pause 200 
    LCDOUT $FE,1   
    goto mainmenu
endif
goto brightness2

up:
    maxbright = maxbright + 1
    IF maxbright > 255 THEN maxbright = 0
    pause 50
RETURN
down:
    maxbright = maxbright - 1
    IF maxbright = 0 THEN maxbright = 255
    pause 50
RETURN

I can't argue with the brackets - all I know when I enter that menu option I can press the up and down buttons and the LCD displays 0% - 100%, and when checked using a diagnostics section which displays the variable value it correctly shows 0 - 255 and 127 for a 50% value - However I'm now using a PCA 9685 chip, which has a resolution of 4095 steps, so the progression is nice and smooth, and all I need is to repeat this but with 4095 steps, ie so 100% = 4095, 1%=40.95 (or 41 as it would need to be an integer) and 50% would equal 2047, but just can't seem to get my head round the calculation (never was any good at percentages at school all those years ago !

Malcolm