Linearizing an LED for 800 pwm steps'?

[Demon]

Try this modification (untested):

...
  if(index = 0) then
    PRINT
    PRINT "DW ";
  else
    if(index MOD 34 = 0) then 'this dictates how many values per line
      PRINT " " 'this puts no comma at the end of the line
      PRINT "DW ";
    else
...

Robert

[HankMcSpank]

Hi, that worked a treat, here's the output after modifying with your snippets...

Gamma array size: 255
 Total PWM steps: 1023
Gamma correction: 2

DW   0,  0,  0,  0,  0,  0,  0,  1,  1,  1,  1,  2,  2,  3,  3,  4,  4,  5,  5,  6,  6,  7,  8,  9,  9, 10, 11, 12, 13, 14, 15, 16, 17, 18
DW  19, 20, 21, 22, 23, 25, 26, 27, 29, 30, 31, 33, 34, 36, 37, 39, 40, 42, 44, 45, 47, 49, 51, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72
DW  74, 77, 79, 81, 83, 86, 88, 90, 93, 95, 98,100,103,105,108,111,113,116,119,121,124,127,130,133,136,139,141,144,148,151,154,157,160,163
DW 166,170,173,176,180,183,186,190,193,197,200,204,208,211,215,219,222,226,230,234,238,241,245,249,253,257,261,265,269,274,278,282,286,290
DW 295,299,303,308,312,317,321,326,330,335,339,344,349,353,358,363,368,373,377,382,387,392,397,402,407,412,417,423,428,433,438,444,449,454
DW 460,465,470,476,481,487,492,498,504,509,515,521,526,532,538,544,550,556,561,567,573,579,586,592,598,604,610,616,623,629,635,641,648,654
DW 661,667,674,680,687,693,700,707,713,720,727,734,740,747,754,761,768,775,782,789,796,803,810,817,825,832,839,846,854,861,868,876,883,891
DW 898,906,913,921,928,936,944,952,959,967,975,983,991,999,1007,1014,1023

Many thanks....this will save me a lot of time experimenting with different gamma values with the LUT going into the PIC

[Mike, K8LH]

Hi Hank,

Sorry for the late reply. Glad you figured it out. Another slightly more recent version of that Gamma Table program is listed below.

Gamma values of 1.7 to 1.9 worked good for me but it's very much dependent on your LEDs, voltage, hardware, etc..

Cheerful regards, Mike

 '  Leo Bodnar's 'antilogarithmic'
 '  gamma correction algorithm (Mike, K8LH)
 '
 '  JustBASIC (free) interpreter
 '
 Input "Gamma array size: "; arraysize
 Input " Total PWM steps: "; width
 Input "Gamma correction: "; gamma       ' try 0.5 to 1.0
 Input "Entries per line: "; entries     '

 FOR index = 0 to arraysize-1
    dcyval = INT(width^(((index+1)/arraysize)^gamma)+.3)
    if(index MOD entries = 0) then
      PRINT
      PRINT "  DW ";
    else
      PRINT ",";
    end if

    if(dcyval < 100) then print " ";
    if(dcyval < 10) then print " ";
    PRINT dcyval;
 NEXT index
 PRINT
 PRINT
 REM CLOSE

[RossWaddell]

Hi Hank,

Sorry for the late reply. Glad you figured it out. Another slightly more recent version of that Gamma Table program is listed below.

Gamma values of 1.7 to 1.9 worked good for me but it's very much dependent on your LEDs, voltage, hardware, etc..

Cheerful regards, Mike

 '  Leo Bodnar's 'antilogarithmic'
 '  gamma correction algorithm (Mike, K8LH)
 '
 '  JustBASIC (free) interpreter
 '
 Input "Gamma array size: "; arraysize
 Input " Total PWM steps: "; width
 Input "Gamma correction: "; gamma       ' try 0.5 to 1.0
 Input "Entries per line: "; entries     '

 FOR index = 0 to arraysize-1
    dcyval = INT(width^(((index+1)/arraysize)^gamma)+.3)
    if(index MOD entries = 0) then
      PRINT
      PRINT "  DW ";
    else
      PRINT ",";
    end if

    if(dcyval < 100) then print " ";
    if(dcyval < 10) then print " ";
    PRINT dcyval;
 NEXT index
 PRINT
 PRINT
 REM CLOSE

Hi Mike,

I'm implementing a LED dimmer using Darrel Taylor's MIBAM library (see http://www.picbasic.co.uk/forum/cont...-Modulation%29) which accepts values from 0 - 255 for the duty cycle. I also want to smoothly fade the LEDs so I believe I need to include something similar to your Gamma correction algorithm, but I'm having trouble understanding what you mean by 'Gamma array size'. On another thread I see you posted a chart where you used 100 for that value (and 512 for pwm steps) - is that analogous to saying, 'My brightness can go from 0 (fully off) -100% (fully on, max LED brightness) with 512 steps'? Would I use Gamma array size = 100 and pwm steps = 256?

[Mike, K8LH]

Would I use Gamma array size = 100 and pwm steps = 256?

Yes... Good luck with your project...

Cheerful regards, Mike

[RossWaddell]

Thanks Mike!

[RossWaddell]

Next question - if this produces data than I **think** gets added to a .pbp file with the ASM/ENDASM block, how do I search/look up values from it in code?