Strange gear tooth sensor port issue

[scottanderson]

WPILib's "GetGTSensor" routine, from the latest release of WPILib.

The code is simply this:

void main(void) {
StartGTSensor(1, 0);
StartGTSensor(2, 0);

while (1) {
printf("1: %d 2: %d 3: %d 4: %d\n", GetGTSensor(1), GetGTSensor(2), GetGTSensor(3), GetGTSensor(4));
}
}

The gear tooth sensors are plugged into ports 1 and 2.

Output:

1: 0 2: <port 1 output> 3: 0 4: <port 2 output>
...

If I invert instead:

StartGTSensor(1, -1);
StartGTSensor(2, -1);

then I see this:

1: -1 2: <port 1 output> 3: -1 4: <port 2 output>
...

Regards,
-scott

[Alan Anderson]

Originally Posted by scottanderson

printf("1: %d   2: %d   3: %d   4: %d\n", GetGTSensor(1), GetGTSensor(2), GetGTSensor(3), GetGTSensor(4));

The problem is probably with the printf() statement, not with the Gear Tooth Sensor code. You're asking for four ints to be printed. It looks like GetGTSensor() returns a long. The first %d will show the first 16 bits of GetGTSensor(1), the second %d will show the rest of GetGTSensor(1), the third will show the first 16 bits of GetGTSensor(2), etc.

If this is the case, you can correct the problem either by printing the values using %ld, or by casting them as (int).

[scottanderson]

Oh, jeez. For some reason I thought that function returned int.

Yes, that probably explains it. Thanks.

Regards,
-scott, who apparently has been programming in Java for far too long.