16F877A won't keep relay on 100% of the time

[Archangel]

Hi coyotegd,
by boilerplate I assume you refer to code that you reuse over and over like TRIS and Config fuse settings, that can be dicey in programming PICs as so many have their own quirks. You might think good thoughts about posting that boiler plate code so as we can smoke it over. You know, I think I would try your code on a port B pin, as Port A has lots of confusing analog stuff to contend with, the process of elimination.
JS

[coyotegd]

Here is the entire program I am working with just to get the relay to operate properly:

@ DEVICE HS_OSC, WDT_OFF, LVP_OFF, BOD_OFF, PWRT_ON, PROTECT_OFF

Define OSC 20

ADCON1 = 7 ' Digital I/O for Registers A & E
TRISA = 0 ' PORTA as outputs
PORTA = 0 ' PORTA pins low
TRISB = 255 ' PORTB as inputs from Mach3
PORTB = 255 ' PORTB pins high for active low
OPTION_REG.7 = 0 ' Enable PORTB pull-up resistors
TRISC = 0 ' PORTC as outputs
PORTC = 0 ' PORTC pins low for active high
TRISD = 0 ' PORTD as outputs
PORTD = 0 ' PORTD pins low for active high
TRISE = 7 ' PORTE as inputs from machine for x, y, z travel limits
PORTE = 7 ' PORTE pins high for active low

ChrgPmp var PORTB.0 ' Input for Mach3 charge pump
CntCP var byte ' Count check for 12kHz on PORTB.0
Estop var PORTA.0 ' Send Emergency stop to Mach3
LPTports var PORTA.1 ' Enable parallel ports
Aux var PORTA.2 ' Auxilary power
Coolant var PORTA.3 ' Coolant power
Spindle var PORTA.4 ' Spindle power
SpinDir var PORTA.5 ' Spindle direction
XLED VAR PORTD.0
YLED VAR PORTD.1
ZLED VAR PORTD.2
X var byte ' Counter for pin cycling

'----------

MAIN:
count chrgpmp, 1, cntcp ' Count freq. on B0, Mach3's 12kHz
if (cntcp >= 11) and (cntcp <= 13) then ' Freq. must be between 11 & 13kHz
lptports = 1
else
LPTports = 0
goto main
endif
'gosub CK_PORTB
'gosub CK_PORTE
goto main
end

[mackrackit]

Are you on the correct pin. At the beginning you said you were using PORTA.2.
Code shows PORTA.1?

What about CMCON = 7

[coyotegd]

You are right, but A2 is correct. When I first posted, I change my code for clarity. I probably should have used the exact same code all the way through. When I said A1 earlier, it should have been A2. Good find. Thanks for looking.

I think everyone should STOP TRYING TO FIGURE THIS OUT. I tested the programmed PIC with a breadboarded darlington and relay and it works like a champ. No split-second low on A2 approximately every second during a proper A2 high when B0 frequency is between 11 and 13kHz.

I must have a conflict in my power supply or other PIC peripheral connections. I'm sure I'll find the answer when I look very closely at my schematic.

Thanks everyone.

[coyotegd]

When I use a 12kHz TTL signal from my Function Generator, the relay works fine. However, when I use the 12kHz signal from Mach3, I get the spastic relay. I scoped the Mach3 signal after passing through the transceiver, it appeared to be a good 12kHz 5V to 0V signal.

I am going to run the Function Generator signal through the parallel port as if it's Mach3's, and thereby through the tri-state transceiver. I'm narrowing it down and will find it.

Thanks for letting me vent.

[coyotegd]

Function Generator 12.1kHz TTL 3V signal directly on B0 and the relay works great. Ditto when the Generator's signal is run through PC parallel port input and tri-state transceiver to boost to 5V square wave.

Mach3 PC software transmitting 3V TTL through parallel printer port. Signal placed directly on B0, spastic relay. Ditto when the signal is passed through the tri-state transceiver.

Both signals look exactly the same on an oscilloscope. Both signals find the same ground as the PIC, relay, transceiver, parrallel port and power supply.

I even took the signal directly from the parallel port attached to the PC in case the cable was defective.

Arghhhhh.....

BTW, I believe "CMCON = 7" would be a moot entry. "ADCON1 = 7" makes ports A and E digital I/O rather than analog.

[mackrackit]

BTW, I believe "CMCON = 7" would be a moot entry. "ADCON1 = 7" makes ports A and E digital I/O rather than analog.

You may want to read this. It explains ADCON and CMCON.
http://www.picbasic.co.uk/forum/showthread.php?t=561