Bit Angle Modulation (BAM) in a PIC

[RadikalQ3]

You can invert the value of the bits in each cycle.

In odd cycles, do first the normal order retard for each bit:
1,2,4,8,16,32,64,128

and, in the even cycles, reverse the value of each bit:
128,64,32,16,8,4,2,1

Edit:
Oops this can generate the problem even without transtitions of the dutty cycle used... hummm... maybe rearranging the value of the bits, not just reversing them :?

[Darrel Taylor]

Hmmmm, such a Radikal idea.
Very interesting ...

I had thought of putting the 7th bit in the middle, but it always came up lop-sided since it's Half of the period.

But making a mirror image of the pulses (at twice the frequency) would put it smack dab in the middle of a nice symetrical waveform that might actually work.

I must try this ...

Oh, and Hi there Q3.
Welcome to the forum!

[anonymouse]

Hmmmm, such a Radikal idea.
Very interesting ...

I had thought of putting the 7th bit in the middle, but it always came up lop-sided since it's Half of the period.

But making a mirror image of the pulses (at twice the frequency) would put it smack dab in the middle of a nice symetrical waveform that might actually work.

I must try this ...

Oh, and Hi there Q3.
Welcome to the forum!

Just my musings can you do a check if duty cycle = 127 + 1 then bit 7=0 (0.005s interrupt) then 128 duty cycle. I.e cause a timer interupt delay before starting on with the BAM again.

[anonymouse]

Just my musings can you do a check if duty cycle = 127 + 1 then bit 7=0 (0.005s interrupt) then 128 duty cycle. I.e cause a timer interupt delay before starting on with the BAM again.

Thats as clear as mud, => 128 begin reverse read byte and vice versa

[Darrel Taylor]

RadikalQ3,

Thanks for the Mirror Image idea!
It has completely removed the blinking problem.

Unfortunately the higher frequency and extra code to reverse things has created some new ones, but I think I can work through them.

For your first post here, it was an awesome one.

Thanks again,

Also, thanks anonymouse,
But with multiple channels at different dutycycles all using the same timer, changing the interrupt sequence at 127 isn't possible.
I hadn't mentioned the multi-channel part yet ... oops.

[RadikalQ3]

RadikalQ3,
Thanks for the Mirror Image idea!
It has completely removed the blinking problem.

Oh, it's nothing... just was an idea.
I have spent the last days reading all I found in internet about PWM, BAM, Frecuency Modulation, etc.
I have a project to do and I am gathering all the information about this topic.
Simply... I found your topic (and this forum) and I thought that was a nice challenge solve your blinking problem O
I am waiting the recepcion of some hardware and in a few days I can do test with this for my own.

Later, I realized that this is a forum on basic! (and I just use assembler)

[Darrel Taylor]

Videos of oscilloscopes never seem to work very well.
But it's interesting to watch the way the mirror image works.

Let's call it BAM-BAM.

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/4eZho2fN3r8&hl=en&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/4eZho2fN3r8&hl=en&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

It's going through a ramp from 0-255 and back down.