Hardware Reference
In-Depth Information
Input change : flags 8000 values F0F0
Outputs : 070F
Input change : flags 8000 values 70F0
Outputs : 0F0F
^C
$
While this was running, I carefully grounded pin 28 of the MCP28017 chip, which is
input
GPA7
. This is reflected immediately in the message:
Input change : flags 8000 values 70F0
The flags value reported as
8000
is decoded next, showing that
GPA7
did indeed
change
in value:
INTFA
INTFB
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
The value reported as
70F0
is from the
INTCAPx
register pair:
INTCAPA
INTCAPB
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
0
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
This shows us that the
GPA7
pin is found in the zero state at the time of the interrupt.
All remaining inputs show high (0s indicate output pins).
While I grounded the
GPA7
pin only once, you can see from the session output that
several events occur. This is due to the
bounce
of the wire as it contacts. You'll also note
that some events are lost during this bounce period. Look at the input events:
1 Input change: flags 8000 values 70F0
2 Input change: flags 8000 values F0F0
3 Input change: flags 8000 values F0F0
4 Input change: flags 8000 values F0F0
5 Input change: flags 8000 values F0F0
6 Input change: flags 8000 values 70F0
