Need help in matrix keypad coding

[tenaja]

The output state of the pin is stored, even when it is an input. When you make it an input, it automatically goes wherever the input is pulling it. As soon as you make it an output, the old output value is restored.

The way to ensure it goes to the desired state is to set the value prior to TRISing it to an output.

[Probotics]

Ah gotcha. So the column is switched to output, then the rows (which are 4 bits over) are examined to see if that row is linked to the column. Thanks - I don't know how I missed it now that I see it. This should help with a keypad with a different number of buttons I've been working on.

[Probotics]

So I remember now why I was having trouble following this. The value of the D port is 0. When set to output it draws the input port low. I didn't realize you had to have pull up resistors in the keypad circuit to keep the input port high whenever not being pulled low. The original circuit using this code that I saw had weak pull up resistors enabled and no external resistors, but the port I was using did not have weak pull up resistors associated with it.