I don't understand this code!

[Russ Kincaid]

Hi Pic_User. Yes, I know that, but why cannot I connect the LEDs to + and pulse to ground? I changed the program, trying to zero in on the probem. Now GPIO.1 pulses to ground like I want but GPIO.0 pulses positive in phase with GPIO.1. I would not expect GPIO.0 to change at all.

high GPIO.0 'INITIAL CONDITIONS
high GPIO.1

START:
low GPIO.1
high GPIO.0
PAUSEUS 4168 ' ON TIME
high GPIO.1
PAUSEUS 4167 'DEAD TIME, BOTH high
high GPIO.1
PAUSEus 4168 'FOR 4.168 MILLISECONDS
high GPIO.1
PAUSEUS 4167 'DEAD TIME

GOTO START '60 HZ FREQUENCY

END

I will post the final circuit so you can see what I am trying to do. I want to replace the 555, flip flops and gate with the PIC.

[Pic_User]

Hi Russ,

Looking at the circuit you want to replace:
It looks like you want to avoid both being on at the same time, at all costs (as you said).

It may be better to declare variable for the “HIGH TIME” and the “anti-overlap” time so you can change them in one place in the program, while playing with the duty cycle.

Could be missing something but it looks like you want the positive part of the cycle to take 8.336 milliseconds and same time for the negative part.
Sixty Hertz = 1/60 = 0.0167 (16.67 milliseconds).
This gives us 16.67 milliseconds for a complete (whole) cycle.

How much on or off time can be played with but the recurring 60Hz, is fixed.
So the total on and off time for GPIO.0 and GPIO.1 should equal 16.67 milliseconds, and never be on at the same time.

I used your same code and beat it up pretty bad:

LOW GPIO.0 'INITIAL CONDITIONS
LOW GPIO.1

START:

HIGH GPIO.1
PAUSEUS 8236 ' HIGH TIME - GPIO.1 only
LOW GPIO.1 ‘both pins low
PAUSEUS 100 ' anti-overlap time
‘ HIGH TIME and over-lap time should add to 8.336 milliseconds

HIGH GPIO.0 ' GPIO.1 has been low during anti-overlap time
PAUSEUS 8236 ' HIGH TIME - GPIO.0 only
LOW GPIO.0 ‘ both pins low
PAUSEUS 100 ' anti-overlap
‘ HIGH TIME and over-lap time should add to 8.336 milliseconds

GOTO START '60 HZ FREQUENCY

END

Play with HIGH TIME and anti-overlap to get the desired duty-cycle (average vs. RMS vs. 0.7 ) but they should total to 8.336 milliseconds each half cycle. Then 16.67 milliseconds for the whole cycle.

You should run the diodes (LEDs) between the PIC pins and the resistor to common (ground).

Oh yeah, I should warn you that I don’t know what I am doing!:>

-Adam-

[Russ Kincaid]

Thanks, but I have already built the board, I don't want to cut traces if I don't have to. My original program produced the inverted waveform, I want to be able to produce the waveform per the sketch. As another experiment, I modified the program, adding another HIGH GPIO.0, but now both outputs go low at the same time for 8 mS.

high GPIO.0 'INITIAL CONDITIONS
high GPIO.1

START:
low GPIO.1
high GPIO.0 'GPIO.0 GOES LOW
PAUSEUS 4168 ' ON TIME
high GPIO.1 ' GPIO.1 GOES LOW
HIGH GPIO.0 'GPIO.0 STAYS LOW
PAUSEUS 4167 'DEAD TIME,
high GPIO.1 ' BOTH GO HIGH
PAUSEus 4168 'FOR 4.168 MILLISECONDS
high GPIO.1 BOTH STAY HIGH
PAUSEUS 4167 'DEAD TIME

GOTO START '60 HZ FREQUENCY

END
GPIO.0 and GPIO.1 are synchronous but I don't know that they follow the program!

[skimask]

high GPIO.0 'INITIAL CONDITIONS
high GPIO.1
START:
low GPIO.1
high GPIO.0 'GPIO.0 GOES LOW
PAUSEUS 4168 ' ON TIME
high GPIO.1 ' GPIO.1 GOES LOW
HIGH GPIO.0 'GPIO.0 STAYS LOW
PAUSEUS 4167 'DEAD TIME,
high GPIO.1 ' BOTH GO HIGH
PAUSEus 4168 'FOR 4.168 MILLISECONDS
high GPIO.1 BOTH STAY HIGH
PAUSEUS 4167 'DEAD TIME
GOTO START '60 HZ FREQUENCY
END

I think you might be confusing yourself a bit...not sure, but that's what it looks like to me...
high GPIO.0 'GPIO.0 GOES LOW ---- GPIO.0 looks like it goes low because the LED goes out. No... it's got 5v on both sides of the LED...no current flow...

I think, in the end, you're going to end up cutting traces and doing some rewiring.

[Pic_User]

This code should work with the LEDs wired the original way.
You could even put a time delay before the ON time and after the ON time, to “push” the waveform around. To get the desired timing to get the quasi sine wave at 60 Hz. I have no idea what timing will help!
Just be sure the total adds up to the times for 60Hz.

START:
PAUSEUS 2074 ' before pulse
LOW GPIO.1 ‘ON = pulse
PAUSEUS 4168 ' ON TIME - GPIO.1 only
HIGH GPIO.1 ‘both pins OFF
PAUSEUS 2074 ' after pulse
PAUSEUS 20 ' anti-overlap time
‘should add to 8.336 milliseconds

PAUSEUS 2074 ' before pulse
LOW GPIO.0 ‘ON = pulse
PAUSEUS 4168 ' ON TIME - GPIO.0 only
HIGH GPIO.0 ‘both pins OFF
PAUSEUS 2074 ' after pulse
PAUSEUS 20 ' anti-overlap time
‘should add to 8.336 milliseconds
GOTO START '60 HZ FREQUENCY

END

I still would like to know between which points are you measuring the wave (voltage) from?

[skimask]

I still would like to know between which points are you measuring the wave (voltage) from?

I'm guessing just looking at the LEDs, not actually measuring voltage...
I could be wrong...been there before

[Pic_User]

I'm guessing just looking at the LEDs, not actually measuring voltage...
I could be wrong...been there before

Bet you’re right. Must be difficult to tell if both come on together at 60 Hz tho...