XOUT and HPWM

[Darrel Taylor]

Hmmm, what I missed was the Polarity of the XOUT signal. The PBP manual didn't really go into too much detail, but i found another document on the web that explained it better. It's description goes like this.

Transmit to Power Line—Output a high on this line within 200 μ of Zero Crossing
going high, and hold the line high, to output a one on the power line—that is, to turn on
the 120 kHz oscillator. Use the same timing with a low output to output a zero. The line
should be low if the interface is not to transmit data, since that keeps the oscillator off.

So, 1 turns the 120khz ON, 0 turns it off.

But with the TRIS bit, it works the other way around. 1 = INPUT (OFF),  0 = OUTPUT (ON). Just a little backwards.

I think you're right though, the only way around it is to change the XOUT command itself. Fortunately, it's an easy change if you're willing to tamper with the PBPPIC14.LIB file.

If so, be sure to make a copy of the file before editing, you might want it back the old way later on.

Your mission, should you choose to accept it, is to ...

Open the PBPPIC14.LIB file in the PBP folder, and do a search for XOUT. You should see a section that looks like this

    ifdef XOUT_USED
  LIST
XOUT2   movlw   2               ; Default to 2 cycles
XOUT    movwf   R2              ; Save number of cycles
        movf    RR1, W          ; Get data port
        movwf   FSR             ; Put it into FSR
        movf    RM1, W          ; Get data bit mask
   ;     call    LOWT            ; Set data to low, output

Comment out the "call     LOWT". We'll handle setting the pin to the correct state manually.

Then scoll down a little bit to xout1loop and change it like this

xout1loop 
   ;     movf  RM1, W           ; Get data bit mask
   ;     iorwf   INDF, F        ; Set the bit
        comf    RM1, W          ; Get inverted data bit mask
        andwf   INDF, F         ; Clear the bit

        movlw   high 1000       ; Pause 1 ms
        movwf   R0 + 1
        movlw   low 1000
        call    PAUSEUSL

   ;     comf    RM1, W          ; Get inverted data bit mask
   ;     andwf   INDF, F         ; Clear the bit
        movf    RM1, W          ; Get data bit mask
        iorwf   INDF, F         ; Set the bit

It just reverses whether it sets the pin high or low.

Now, to use it ..

    TRISB.3 = 1          ' start with output OFF
    XOUT TRISB.3,PORTA.0,[house\lightsOff]

Fingers crossed

P.S. Don't blame me if you don't backup the file first.

[ardhuru]

Darrel, that was brilliant!

Worked the first time. If I wore a hat, i'd have raised it now.

Thanks and regards,

Anand

[ardhuru]

Darrel, whatever you suggested in the earlier messages worked perfect, and that's made me more ambitious/adventureous/greedy.

What I wonder is, can this also be achieved using your popular timer0/1 based PWM techniques (instead of the PIC's HPWM) to modulate the XOUT signal? The idea being able to use this with any pic, and on any pin.

Thanks in advance.

Regards,

Anand

[Darrel Taylor]

Hi Anand,

I think at 120kz, the interrupts required to generate that frequency on ANY pin (250,000 per second) would interfere with the timing of the XOUT command.

I can't think of an easy way off hand.

DT

[ardhuru]

Oh, okay.

Nothing like actually trying it out, I guess.

Referring to some of your earlier posts I think I should be able to see if it flies.

Shall keep this thread posted for the benefit of others, if it works.

Thanks for all the inputs, Darrel.

Anand

[dhouston]

Anand,

The 8-pin 12F683 has HWPM and only costs slightly more than the 12F629 or 12F675. I posted a simple example of turning it on/off using ~120kHz with 1ms bursts at 10ms intervals in another thread recently. Here it is again...

DEFINE OSC 8
@ DEVICE PIC12F683, INTRC_OSC_NOCLKOUT, MCLR_OFF

TRISIO.2 = 0				'GPIO.2=Output
PR2 = 17			        'PWM Period   117.7kHz
CCPR1L = 8				'PWM Duty-Cycle  
T2CON = %00000100    			'Timer2=ON, 1:1 prescale
OSCCON = %01110001                      'INT HF OSC 8MHz
WHILE OSCCON.3>0: WEND                  'OSC startup timeout
WHILE OSCCON.2=0: WEND                  'INT HF OSC stable
WHILE OSCCON.2>0 
  CCP1CON = %00001100 'PWM ON
  PauseUS 1000        'generate 1ms burst 
  CCP1CON = 0         'PWM OFF
  Low GPIO.2
  Pause 10            'pause 10ms
WEND

The disadvantage of using XOUT is that it cannot send microdim/microbright and cannot send the extended commands X-10 introduced 6-7 years ago.

[Darrel Taylor]

Hey Anand,

Still using the 628A ?
and what OSC ?

I think I have something for you.

DT

[ardhuru]

Hi Darrel,

Yes, still on the 16F628, with the internal 4 Mhz oscillator, although I'm hoping to migrate it to an 8 pin (or even 6?) device.

I could of course use an 12F683 as Dave pointed out, but I'm still curious to see if this can be done without the HPWM module.

Very eager to see your suggestion!

Anand