Bit Angle Modulation (BAM) in a PIC

[Mike, K8LH]

Hi Darrel,

I think we may be confusing each other with terminology and perhaps a slight difference in our design. I was using "1T" as the PWM step size. For example, if we were to use a step size of 10-usecs and 256 steps or levels then we'd have a 2560-usec period (256*10-usecs). The b0 output is 10-usecs or 1T long. The b1 output is 20-usecs or 2T long but I split it in half with 10-usecs or 1T on either side of the b0 10-usec (1T) output. That's how I get |2T|1T|1T|1T|2T| == |20us|10us|10us|10us|20us| == |half b2|half b1|full b0|half b1|half b2|. I thought this was how you were doing it but now I suspect I didn't look closely enough at your code and I apologize.

It also seems you think I'm combining the b2, b1, and b0 outputs and reducing resolution but I'm not. I'm simply generating the b2, b1, and b0 outputs during a single interrupt interval.

More later... I'm trying to see if I can upgrade a very old 12F683 Charlieplexed 5-pin 20-LED project from 64 levels per LED to 256 levels per LED using MIBAM. Wish me luck...

Kind regards, Mike

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[boroko]

Is it possible to combine MIBAM and DT_INTS?

I am attempting to use MIBAM in a program where I have been using SPWM_INT. I understand that MIBAM need exclusive use of TMR1 and HI priority INTs. The thought was to see if I could still use DT_INTs to handle low priority ints for a pulse time capture and a HSER routine. I still have to play with it to decide if I can make them function with the probability of MIBAM cutting off the other two, but that is a separate problem.
The issue that I see is that DT_INTS has:
"DEFINE INTHAND INT_ENTRY_H"
"DEFINE INTLHAND INT_ENTRY_L"
and MIBAM has:
"DEFINE INTHAND doBAM"
Can the doBAM section be added to the INT_ENTRY_h section and eliminate the "DEFINE INTHAND doBAM"? If so how?

Until I understand this better, I'm going to continue with the SPWM_INT version of the code and work on finishing the rest of the code that way. I may not need the advantages of MIBAM, but it sure is a cool routine. Even with my limited coding ability, DT's routines have multiplied my capabilities tremendously. Thank you Darrel and all the others that have put in the effort and patience and have been willing to share your wisdom so freely.


Bo

[Darrel Taylor]

Since MIBAM uses a completely ASM interrupt handler, it would be much easier to make it compatible with DT_INTS instead of the other way around.

However, if you're just measuring pulse widths ... the use of Timer3 and a CCP module (Capture mode) might be more applicable. And you won't need Interrupts for that, although they can still be used with LOW Priority. It'll be more accurate with the CCP too.

The HIGH Priority interrupts will affect the "Timing" of LOW Priority ints.
The resolution of a Pulse measurement using LP ints (without CCP) will always suffer.
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[sanch0]

The HIGH Priority interrupts will affect the "Timing" of LOW Priority ints.
The resolution of a Pulse measurement using LP ints (without CCP) will always suffer.
<br>

what means "LP ints"? Are u talking about jitter problem? U should update T0 then (for example) in every interrupt to avoid that. If u going to use CCP with prescalers/postscalers then will get jitter error too.

What refresh rates and bit resolutions have u achieved?

p.s. very nice aproach, congratulations. and sorry 4 poor english.(

[Darrel Taylor]

"LP ints" means Low Priority Interrupts on an 18F.

High Priority Interrupts can interrupt Low Priority Interrupts.
So trying to measure times exactly with Low Priority interrupts will not give very good results unless you are using hardware peripherals, like the CCP module.
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[Darrel Taylor]

Mike,

Did you get anywhere with this ...
I can not figure out a way to Charlieplex MIBAM.

I need to finish this thing, and think I'm going to have to toss Charlie out the window (from a very tall building).

DT

...
More later... I'm trying to see if I can upgrade a very old 12F683 Charlieplexed 5-pin 20-LED project from 64 levels per LED to 256 levels per LED using MIBAM. Wish me luck...

Kind regards, Mike

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[Mike, K8LH]

What "thing" are you talking about tossing Darrel?

I wrote and simulated the ISR driver for a 5-pin 20-LED demo' but that's as far as I got. You want to see that part Sir?

<added>

Tell me what chip you want it for and I'll give you a simple 5-pin (rb0..rb4) 20-LED sample Saturday that you can breadboard and play with.

Mike

[Darrel Taylor]

What "thing" are you talking about tossing Darrel?

At this point, I'd like to toss Charlie Allen himself.

I wrote and simulated the ISR driver for a 5-pin 20-LED demo' ...

Is that with MIBAM? I'd love too.
For whatever chip, in whatever language.

Even if it's not MIBAM, it might give me an idea that could save Charlie's life.

Thanks again Master,

[Mike, K8LH]

Yes, it's a sample ISR engine for MIBAM within an assembly language 'skeleton' program for 16F886 with 20 Charlieplexed LEDs on 5 pins (RB0..RB4). Just needs config lines, an init section, and short main section to manipulate the led[] array. I was interested in seeing if MIBAM could be implemented on a Charlieplexed matrix and after I wrote and simulated the MIBAM ISR 'engine' I got distracted by other projects.

I will send you the Charlie-MIBAM skeleton in a PM and work on those missing pieces so that you can actually try something on some hardware, if you like.

Mike

[Mike, K8LH]

Someone asked about the diagonal line on my Charlieplexed display sketch. It's what I refer to as the "float" pin and it's connected to the LEDs that occupy positions in the matrix that would otherwise share a common column and row (RB0/RB0, RB1/RB1, etc.).

I apologize if the diagonal line has thrown you off. It's a remnant from some of my sketches of Charlieplexed 7-segment displays.

Both drawings below are electrically the same but the second drawing below may make more sense. Basically I just slid those LEDs in the bottom row up into the empty spaces in the matrix.

Kind regards, Mike

[Mike, K8LH]

Darrel,

I was just wondering -- is MIBAM even necessary on a multiplexed display due to the long pauses between LED activation. You know, column one LEDs would be BAM'ed then turned off while we sequencially BAM column two LEDs, then BAM column three LEDs, etc.?