Hi Rich,

There are a couple of ways you could do this. One would be to use arrays
to decode the inputs. It would probably be efficient. The second would
be to use a switch-case statement. It is more versatile. If you decide
to add more features, it'll come in handy. So that's what I'll do here
for your Port A question, you can duplicate this for Port B and change
it as necessary.

void decodePortA(void)
{
unsigned char portashadow =3D PORTA & 0xC3;  // zero out the bits we write
later
  // If you are driving port A during interrupts, disable interrupts
  here
  switch (PORTA & 0x03)  // only working with bits 0 and 1
    {
      case 0:
        portashadow |=3D 0x24;  // output bits 2 and 5
        break;
      case 1:
        portashadow |=3D 0x08;  // output bit 3
        break;
      case 2:
        portashadow |=3D 0x10;  // output bit 4
        break;
      case 3:
        portashadow |=3D 0x20;  // output bit 5
        break;
      }
      PORTA =3D portashadow;  // write the decoded pattern to the port
      // If you disabled interrupts earlier, re-enable them here
}

Sorry if formatting isn't great, using email editor.

Using switch-case takes more steps, but it's real clear what you are
doing, and you can do completely different things or additional steps
for any case.

Hope this helps.  I haven't used XC8 but this should be portable. If I
made errors, sorry, I'm sleepy :(

Best regards, Bob

On Sat, Sep 12, 2015, at 09:49 AM, Richard R. Pope wrote:
> Hello all,
>      I solved this problem. Some how I managed to delete everything in=20
> the XC8 include files. I reinstalled XC8 and that fixed it. Dumb!! Now I=
=20
> have another problem. The code is running and most of it works=20
> correctly. This is about as simple as it gets. I am using a series of if=
=20
> and elseif statements to check for the setting of two input bits and=20
> then set four output bits. It is PortA and B and the input bits are 0=20
> and 1. The two ports control two separate devices. If the setting is 0,=20
> 0 then output bits 2 and 5 are on and bits 3 and 4 are off. If the=20
> setting is 0, 1 then bit 2, 4, and 5 are off and bit 3 is on. If the=20
> setting is 1, 0 then bits 2, 3, and 5 are off and bit 4 is on. If the=20
> setting is 1, 1 then bits 2, 3, and 4 are off and bit 5 is on. That is=20
> the way it is supposed to work. So here are three tables showing what is=
=20
> supposed to happen and what is happening;
>                              Supposed to be!                 The way it=20
> is!   Port A      The way it is!   Port B
> --------------------------------- ----------------------------------    =
=20
> ----------------------------------
>                  |    Input    |    Output                 |          =20
>          |    Input    |    Output |     | Input    |    Output     |
>                  |   Bits       |    Bits                      |     =20
>                    |    Bits      |    Bits       | |    Bits      |   =20
> Bits                        |
>                  |-----|-----|-----|-----|-----|-----|            =20
> |-----|-----|-----|-----|-----|------|=20
> |-----|-----|-----|-----|-----|------|
>                  |   1  |   0   |   2   |   3  |   4  |   6   | 5 for=20
> B          |   1   |   0  |   2   |   3  |   4   |   6 |     |   1 |  =20
> 0  |   2  |   3   |   4   |   5   |
>                  |-----|-----|-----|-----|-----|-----|            =20
> |-----|-----|-----|-----|-----|------|      =20
> |-----|-----|-----|-----|------|-----|
>                  |   0   |   0  |  1   |   0   |   0   |   1  |       =20
>                  |   0  |    0  |   1   |   0  |    0  | 1   |    OK    =
=20
>       |   0  |   0   |   1  |   0   |   0    | 1  |        OK
>                  |-----|-----|-----|-----|-----|-----|            =20
> |-----|-----|-----|-----|------|-----|       =20
> |-----|-----|-----|-----|------|-----|
>                  |   0   |  1   |  0   |   1   |   0   |   0 |       =20
>                  |   0  |    1  |   0  |   1   |    0 |   0  |     OK=20
>          |   0  |   1   |  1* |   0   |   0 |   1*|        Bad*
>                  |-----|-----|-----|-----|-----|-----|            =20
> |-----|-----|-----|-----|------|-----|       =20
> |-----|-----|-----|-----|------|-----|
>                  |   1   |   0  |   0  |   0   |   1   |   0  |        =20
>               |   1   |   0  |   0  |   0   |  1*   |   0   |     OK* =20
>      |   1  |   0   |   0  |    0  |    1   |   0 |        OK
>                  |-----|-----|-----|-----|-----|-----|            =20
> |-----|-----|-----|-----|------|-----|       =20
> |-----|-----|-----|-----|------|-----|
>                  |   1  |   1   |   0   |   0  |   0   |   1 |       =20
>                  |   1  |    1  |   0   |   0  |    0 |   1   |    OK   =
=20
>       |   1  |    1  |   0  |    1  |    0 |   0  |        Bad
>                  |-----|-----|-----|-----|-----|-----|            =20
> |-----|-----|-----|-----|------|-----|       =20
> |-----|-----|-----|-----|------|-----|

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