[DonRotolo]

Before Hybrid Mode starts, you really can't read anything, since the robot is 'disabled', but in the first microsecond of the match, the gyro is at rest (as is the robot) and so the reading you get should be zero.

If your concern is some kind of calibration to know what "not turning" looks like, I don't think you have to worry much, just read the value in that first microsecond. If the value happens to be read before that - such as when you snap the power on when setting the robot onto the field - then it's a bonus.

The sensor is very well-behaved in our experience - zero means zero, it did not really drift or move enough to worry about. In our 2007 'bot, we never looked for an initial value, we just used whatever the reading came back as and never saw any issues

We're thinking that we'll be using the gyro to help with those 180 degree left turns.

Good luck,
Don

[Edit: Maybe this needs to be tried. Our experience may be different from yours]