I don't understand this code!

[Russ Kincaid]

I am trying to generate a quasi sine wave at 60 hz. The program runs but the waveform is upside down. I could change the circuit to accept the upside down wave, but I would like to know what is going on. This is my simple code:
REM DEVICE = 12F675 '12F629 CAN ALSO BE USED
REM USE INTERNAL OSCILLATOR, OUTPUT IS ON GP4 (PIN 3)
REM CONFIGURATION: INTOSC CLOCKOUT, WDT DISABLED, PWR UP ENABLED,
'MCLR = OUTPUT PIN, BROWN OUT DISABLED, NO PROTECTION
REM 60 HZ OUTPUT IS ON PINS 7 AND 6
REM OSCILLATOR CHOICE: USE 101, INTOSC, CLKOUT
OPTION_REG.5 = 0 'OTHERWISE GPIO.2 IS AN INPUT
TRISIO = %111111 'SETS ALL PORTS TO OUTPUT
ANSEL = 0 'SETS ALL DIGITAL MODE
DEFINE OSCCAL_1K 1 'FOR OSCILLATOR CALIBRATION, DON'T KNOW HOW IT WORKS

HIGH GPIO.0 'INITIAL CONDITIONS
HIGH GPIO.1

START:
LOW GPIO.1
PAUSEUS 4168 ' ON TIME
HIGH GPIO.1
PAUSEUS 4167 'DEAD TIME
LOW GPIO.0 'SETS PIN 7 LOW
PAUSEus 4168 'FOR 4.168 MILLISECONDS
HIGH GPIO.0
PAUSEUS 4167 'DEAD TIME

GOTO START '60 HZ FREQUENCY

END

If I change all highs to lows and all lows to high in the loop, I get the idenical same hex code. I would expect that
high gpio.0
highgpio.1
start:
low gpio.1
would give a different hex code than
high gpio.0
high gpio.1
start:
high gpio.1

Russ

[Pic_User]

Hi Russ,

Could you explain how the waveform is upside down?
Do you mean that the 60 Hertz quasi sine wave is upside down on your oscilloscope display? Switch your scope “triggering” from plus(+) to minus(-).

-Adam

[Russ Kincaid]

Thanks, I should have said that: I want the output to be low for the short time (4+ms) and high for the long time (12+ms). I think the program should do that, but it doesn't. The output is high for the short time and low for the long time.

[languer]

Your main code looks fine:

START:
LOW GPIO.1 
PAUSEUS 4168 ' ON TIME
HIGH GPIO.1
PAUSEUS 4167 'DEAD TIME 
LOW GPIO.0 'SETS PIN 7 LOW
PAUSEus 4168 'FOR 4.168 MILLISECONDS 
HIGH GPIO.0
PAUSEUS 4167 'DEAD TIME

Your startup code does not:

TRISIO = %111111

This sets all pins to <U>inputs</U>. You want to use:

TRISIO = %001000 '(since GPIO3 is input only anyway)

[skimask]

TRISIO = %001000 '(since GPIO3 is input only anyway)

Except for the fact that HIGH and LOW automatically set the pins as outputs...

Now then...what is this output thing? Is this a 2 bit R/2R D/A ladder type setup or what is it?

[mister_e]

If it was me, i would use a timer interrupt, but add somes extra filter outside.

I don't understand what you mean by

The program runs but the waveform is upside down. I could change the circuit to accept the upside down wave,