Hi there, David.

Which microcontroller are you using?  I'm guessing that it's one of=20
the larger devices - but no matter, I guess.

I would be looking at the following:

1) Are you sure that you are actually manipulating the TRIS=20
register?  Wrong bank, for example?
2) Are there any configuration registers that disable the digital=20
input for that pin?  Eg. anything analog that might use that pin?

I know that the above are obvious things that you have already looked=20
at but I'm just reiterating them.

dwayne


At 04:03 PM 11/6/2019, David Van Horn wrote:
>I'm having what seems a pretty bizarre problem.
>I'm using bit 14 of port A as an input to tell me when I need to=20
>pick up data from an ADC.
>I am absolutely sure the pin is toggling low, but when I read the=20
>pin it's always 1 in the port register.
>I'm aware of the AD1PCFG register which could cause this, but AFAIK=20
>that only affects PORTB
>Fortunately, I'm using the PICKit4 ICE, so I can see the register=20
>states as commented below.
>My init routine sets TRISA bit 14 high, and that's all that should matter.=
..
>
>What would cause bit 14 of PORTA to always read high when the pin=20
>itself is low?
>
>
>int ADC_Check_Data() {
>     int temp =3D 0;
>
>     temp =3D PORTA; // Get the pin states
>     // temp =3D 0x0000C0FF at this point, bit 14 is high though the=20
> pin itself is LOW.
>     temp &=3D (1 << 14); // mask off all but bit 14
>     // Here I always get 0x00004000 Bit 14 is HIGH when the pin=20
> itself is LOW.
>     // AT THIS MOMENT:
>     // LATA =3D 0x0000C0FF
>     // ODCA =3D 0x00000000
>     // PORTA =3D 0x0000C0FF (shows bit 14 =3D HIGH)
>     // TRISA =3D 0x0000C0FF (shows bit 14 as INPUT)
>     // Low =3D data ready for reading.
>     if (0 =3D=3D temp) {
>         return 1;
>     } else {
>         return 0;
>     }
>}
>
>--
>David VanHorn
>Lead Hardware Engineer
>
>Backcountry Access, Inc.
>2820 Wilderness Pl, Unit H
>Boulder, CO  80301 USA
>phone: 303-417-1345  x110
>email:=20
>david.vanhorn@backcountryaccess.com<mailto:david.vanhorn@backcountryaccess=
..com>


--=20
Dwayne Reid   <dwayner@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
780-489-3199 voice   780-487-6397 fax   888-489-3199 Toll Free
www.trinity-electronics.com
Custom Electronics Design and Manufacturing

--=20
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