Bit Angle Modulation (BAM) in a PIC

[Darrel Taylor]

One word describes this software.
<script language="JavaScript" src="http://www.pbpgroup.com/js/ColorText.js"></script>
<div id="DTtext"><b>A M A Z I N G !</b></div>
<script>ColorText("DTtext",['red','green','blue','magenta','cyan','black']);</script>

Thanks Ioannis, and I ... uh ... may have embellished your quote a little. (Shameless )

P.S. About the case sensitivity, is this going to have any side effects on other programs that I develop?

I guess that depends on how much ASM code you've been writing.

The default for MPASM is "Case Sensitive".
The default for MicroCode Studio is "Case Sensitive".
So somewhere along the way, you've changed the setting in MCS, and it may or may not have solved your problem at the time. Sometimes you just try things ... grasping for answers.

Why did that happen right now?

Because I chose to use tricky things that require case sensitivity.

The sensitivity option has no effect on PBP statements, since PBP isn't case sensitive to begin with.
And there are some ASM problems that can come up when un-checking the "Case sensitive" box, so I'd recommend leaving it checked at all times.

[Ioannis]

OK. Thanks for the explanation. I will keep the option checked for case sensitivity. I really cannot recall un-checking it...

About the Light intensity control, at least for small 5mm Leds, at low levels there is a problem because of the nature of the diodes. Of course it has nothing to do with the code you have developed.

I suppose that there should be a non-linear function to increse the current at low levels, maybe an exponential or geometric function. Some experimentation will be necessary.

Anyway, having 20 devices to control with a kind of PWM is fantastic.

Once again, you are #1!

Ioannis

[Bruce]

Very smooth fading effect. Nice job DT.

[Darrel Taylor]

Thank you Bruce!

And thanks for the Cylon Scanner.

I mentioned it earlier, and I did end up using the Cylon program we were playing with a while back.

To get the Mirror Image, it scans back and forth just like we had it. Then it uses that to mask the current bit in the dutycycles. It really knocked the code size down.

I used your Cylon version, of course.
<br>

[gmglickman]

Ioannis:

You might want to remap the LED's brightness curve to compensate for the non-linearity in perceived brightness.

This are the values I use

data @$0, $00,$00,$01,$01,$01,$01,$02,$02,$02,$03,$03,$03,$04,$04,$04,$04,$05,$05,$05,$06,$06,$06,$07,$07,$07,$08,$08,$08,$09,$09,$0A,$0A
data      $0A,$0B,$0B,$0B,$0C,$0C,$0C,$0D,$0D,$0E,$0E,$0E,$0F,$0F,$10,$10,$10,$11,$11,$12,$12,$13,$13,$13,$14,$14,$15,$15,$16,$16,$16,$17
data      $17,$18,$18,$19,$19,$1A,$1A,$1B,$1B,$1C,$1C,$1D,$1D,$1E,$1E,$1F,$1F,$20,$20,$21,$21,$22,$23,$23,$24,$24,$25,$25,$26,$27,$27,$28
data      $28,$29,$2A,$2A,$2B,$2B,$2C,$2D,$2D,$2E,$2F,$2F,$30,$31,$31,$32,$33,$33,$34,$35,$35,$36,$37,$37,$38,$39,$3A,$3A,$3B,$3C,$3D,$3D
data      $3E,$3F,$40,$40,$41,$42,$43,$44,$44,$45,$46,$47,$48,$49,$49,$4A,$4B,$4C,$4D,$4E,$4F,$50,$51,$51,$52,$53,$54,$55,$56,$57,$58,$59
data      $5A,$5B,$5C,$5D,$5E,$5F,$60,$61,$62,$63,$64,$65,$67,$68,$69,$6A,$6B,$6C,$6D,$6E,$6F,$71,$72,$73,$74,$75,$77,$78,$79,$7A,$7B,$7D
data      $7E,$7F,$81,$82,$83,$84,$86,$87,$89,$8A,$8B,$8D,$8E,$8F,$91,$92,$94,$95,$97,$98,$9A,$9B,$9D,$9E,$A0,$A1,$A3,$A4,$A6,$A7,$A9,$AB
data      $AC,$AE,$B0,$B1,$B3,$B5,$B6,$B8,$BA,$BB,$BD,$BF,$C1,$C3,$C4,$C6,$C8,$CA,$CC,$CE,$D0,$D1,$D3,$D5,$D7,$D9,$DB,$DD,$DF,$E1,$E3,$E6

Then just

READ LED, LED

[Ioannis]

Hi gmglickman,

Hmm, nice, thanks for the post. I was thinking more complicated on this!

Ioannis

[Caius1]

Hi,

I came across this topic when browsing for BAM.

Regarding the blink can you verify that the blink still occurs when:
1 The last value of the period = 2^nBits - 2 instead of 2^nBits-1
2 New value is only updated at the start of a pwm period.

It would seem strange to me if it does.
I think that a blink can only occur form value=0 to value=x

Thanks

[Darrel Taylor]

Regarding the blink can you verify that the blink still occurs when:
1 The last value of the period = 2^nBits - 2 instead of 2^nBits-1
2 New value is only updated at the start of a pwm period.

I assume you mean reversing the order of bits 6 and 7.

Yes, the blink still occurs. It just happens at different numbers.
No matter which way you order the bit's, if they are only scanned in one direction, there will always be a blink at some point.

I also found that at other points in the dutycycle, the original BAM has several more less obvious blinks as the phase shift does the exact same thing in the lower bits. You just can't see them as well because they are shorter periods. But if you stare right at the LED straight on, you can definitely see them.

However, the symmetrical nature of the Mirror Imaged waveform, completely eliminates ALL of the blinking. It's really amazing how well it fixed the problems.

You can see how it works from the animation in this thread ...

MIBAM - (Mirror Imaged Bit Angle Modulation)
http://www.picbasic.co.uk/forum/showthread.php?t=10564

[vtt-info]

Hi Darrel.

I am testing your Cylon Scanner
code on a 887 chip at 8MHz.

I am stuck on this error:

Error[118] c:\pbp\mibam-~1.asm 97:Overwriting previous address contents (2007)

In fact, the code is a copy of the example. Nothing more or less. Of course the part about wsave is included too. Attached is the final test code.

Regards,
Konrad
MIBAM_Cylon.pbp.txt