Can't make RA1 a digital Input on (10 out of 20) 16F887.

[Archangel]

I thought I had my large code finalized, and now half of my boards have a problem.

The RA1 input always reads 0. I have ANSEL = 0, ANSELH = 0, and have various settings of the other registers from the datasheet.
I also tried using the alldigital.pbp include file.

So in summary, You have 20 pics all programmed alike, and only half work as expected?
Perhaps you have gotten some sour hardware . . . perhaps?
Can you toggle those pins with a simple code, apart from this program?

[paulgrut]

Yes. I have 20 boards with the PIC soldered in. And on half the RA1 input does not work.

I am able to make the RA1 act as an output and it works correctly on all of them.

I am seeing 2 different silicon date codes on the chips, but the problem is with some of each.

The circuit boards are all from the same batch.

The RA1 input is held high with 10K pullup resistor to 5V. The switch pulls this to ground. I have verified the voltage on the chip pin
and it changes from 5V to 0V with the switch. I am going to look over all the ground traces and make sure there isn't (as Henrik asked)
a seperated ground. Although the boards all look to be in good shape.

Thanks for any other ideas. I might order some new 887's and see what happens. And some sockets also...

Paul

[towlerg]

I realize it's a pain to unsolder two PICs but the obvious thing to try is swapping the PIC from a working board to with the PIC from a non working board. Cold comfort but at least you will have a better idea if its the board or the PIC. Are the PICs DIP or SMD? If they're SMD try ChipQuik. BTW there is an errata for the 887, didn't see anthing obvious. George

[paulgrut]

Update.

All of the Ground traces are correct and tied together.

But....After checking again. RA1 WILL NOT work as an output either.

I will swap 2 of the chips. I agree, it is the next step. Not too bad...they are DIP.

Paul

[paulgrut]

Swapped the pic on a working board and a not working board....

Problem stayed with the pic. Must be a pic problem.
Just can't help but think I have something configured wrong in the code.
What could cause a pic failure? These boards were built then tested bad. (no extended use) .

Paul

[towlerg]

have you verified the code in the working and non working PIC's?

[Archangel]

What could cause a pic failure? These boards were built then tested bad. (no extended use) .

Paul

Static Electricity, short circuit, overload, bad programmer (device). What was the source of those PICs ? Microchip, Mouser, FleaBay ? Lots of Fake Chips out there, maybe you got unlucky that way . . . you gotta ask yourself, "What do electronics manufacturers do with parts that do not meet their high standards?". I would bet they wholesale them to somewhere in unmarked condition as scrap and they mysteriously get marked and marketed as "genuine". I am very dubious about off list suppliers.

[Art]

%000000010
%00000010

They are both the same number.

Google RA1 Digital, and you can see the pain!

if portA are all digital inputs, what value do you get reading portA into a byte?

byte = PORTA;

What happens if you do this:

HIGH PORTA.0
PAUSE 250
LOW PORTA.0
PAUSE 250

So that portA isn't powering an LED while A1 is being read?

[Archangel]

This is your code tweaked for a PIC16F690, and it works:

#CONFIG
    __CONFIG _INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _MCLRE_OFF & _BOR_OFF & _FCMEN_OFF & _IESO_OFF 
;__config _CONFIG2, _WRT_OFF & _BOR40V
#ENDCONFIG


DEFINE OSC 20

ANSEL = 0
ANSELH = 0
ADCON0 = 0
ADCON1 = 0
CM1CON0 = 0
CM2CON0 = 0
CM2CON1 = 0
CCP1CON = 0
;CCP2CON = 0
portb=0
portc=0
porta=0
TRISA = %00000010
TRISB = 0
TRISC = 0
;TRISD = 0
;TRISE = 0


Startup:
LOW PORTA.0
PAUSE 250
HIGH PORTA.0
PAUSE 250

IF PORTA.1 = 0 THEN
LOW PORTc.1
ELSE
HIGH PORTc.1
ENDIF
GOTO Startup

The registers a 690 does not have have been commented out. You will need a pull up on your input pin.
Sorry I don't have an 887 to test upon.