Bam test

[Mike - K8LH]

That example was for an 8 bit timer. I understand updating 16 bit timers may involve updating each half of the register in a certain order.

 

[OlPhart]

16 bit timer registers have an interlock: write to either half requires a write to the other to be accepted, it'll just hang until the 2nd write. Checkout any of Freescales' 9S08 series uC w/TPM, flexible enough to be confusing but can do a lot.

I'm just old enough to not get this "bam" nonsense. PWM has been around since before LEDs existed, so how can an LED company patent or copyright it? Am I missing something? Let these clowns sue Allen Bradley or GE over the use of PWM... I'll make popcorn for that movie..... <<<)))

 

[tubos]

@Mike yes that was what I was doing in that 'strange code'
it was only to see if I could get the timings right with TMR0
at higher refreshes in 16bit mode.
With your tip I might as well change to 8bit mode in TMR0
and still have good timings.(thats my project for today )
Edit: Thought this over and won't work at bit0 since there is only
1 or 2 counts so back to 16bit mode.


@OlPhart I'm only trying BAM to get more free CPU time for
doing other stuff while maintaining a high Bit Depth for my matrix
an because I like learning new PicStuff also.
I also find it unbelievable that PWM is patented.

 

[tubos]

Code below should dim led according to level values.
But I experience strange behaviour.
Can anyone spot an error?

UPDATE: I think my isr took too many cycles and thats why it behaved oddly

if(PIR1.CCP1IF) // CCP1 REGISTER COMPARE TMR3 Interrupt?
   {
     sCCPR1=BamH;
     sCCPR1<<=4;  // (changing this to 7 and then it works????)
     CCPR1=sCCPR1;
     itmp=0x01;
     itmp<<=Bambit;
     if(gamma[level] & itmp) LEDRED=1; else LEDRED=0;

     asm INCF   _BAMbit+0, 1       //
     asm MOVLW  7                  //
     asm ANDWF  _BAMbit+0, 1       // BAMbit = ( BAMbit+1 ) & 7
     asm BZ LBL00                  // if(Bambit==0) BamH= 0b11111110;
     asm RLCF _BamH                // BamH<<=1;
     asm GOTO LBL01                // Were done for now
     asm LBL00:
     asm MOVLW 0b00000001          //
     asm MOVWF _BamH               // BamH= 0b11111110;
     asm LBL01:


     PIR1.CCP1IF = 0;    // clear T0 Int flag
    }

 

[tubos]

Here's my optimized isr for BAM total code is approx 60 cycles
So that leaves me about 60 for the 1T interval .
I've been saving some registers on isr entry and restoring them
back at the end , but I don't know if its really necessary.

if(PIR1.CCP1IF) // CCP1 COMPARE TMR3 16mhz  (1T=128 cycles) refrsh = 488 hz
   {              // Total now is 60 cycles
     asm MOVWF _BamL               // Save W
     asm MOVFF STATUS,_sSTATUS     // Save STatus
     asm MOVFF FSR0L,_sFSR0L       // Save STatus
     asm MOVFF FSR0H,_sFSR0H       // Save STatus
// Load next BamTiming
     asm MOVFF _sCCPR1H,CCPR1H
     asm MOVFF _sCCPR1L,CCPR1L
// Start Precalc
// itmp<<=Bambit (51 cycles optimized to 7 cycles)
     asm MOVLW 0x90                // masks[] at 0x90
     asm MOVWF FSR0L               // Point to masks[]
     asm CLRF FSR0H
     asm MOVF _Bambit,0            // Store in W
     asm ADDWF FSR0L,1             // Store in F
     asm MOVFF INDF0,_itmp

     if(gamma[level] & itmp) LEDRED=1; else LEDRED=0; // 20 cycles

     // LEDRED^=1;                    // Invert Bit at LATA,2
// BAMbit = ( BAMbit+1 ) & 7 and calculate next CCP COMPARE value
     asm INCF   _BAMbit+0, 1       //
     asm MOVLW  7                  //
     asm ANDWF  _BAMbit+0, 1       // BAMbit = ( BAMbit+1 ) & 7
     asm BZ LBL00                  // if(Bambit==0) BamH= 0b11111110;
     asm RLCF _BamH                // BamH<<=1;
     asm GOTO LBL01                // Were done for now
     asm LBL00:
     asm MOVLW 0b00000001          //
     asm MOVWF _BamH               // BamH= 0b11111110;
     asm LBL01:
// sCCPR1<<=7; // Takes > 40 cycles  optimized to 6 cycles
     asm CLRF _sCCPR1L
     asm MOVFF _BamH,_sCCPR1H
     asm RRCF _sCCPR1H,1           // Rotate Right store in F
     asm BNC LBL02
     asm BSF _sCCPR1L,7            // Set bit 7
     asm LBL02:                    // Result 0BBBBBBB:B0000000 / 1T=128 cycles
     
     PIR1.CCP1IF = 0;    // clear T0 Int flag
     asm MOVFF _sFSR0H, FSR0H   // Restore FSR0H
     asm MOVFF _sFSR0L, FSR0L   // Restore FSR0L
     asm MOVFF _sSTATUS, STATUS // Restore STATUS
     asm MOVF _BamL,0           // Restore W

    }