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Here's some updates and news from FIRST^®Tech Challenge.

In this week's blast:

📱 Tech Tip of the Week - Gamepad Calibration

👩‍🏫 FIRST^® Certified Professional Development

Tech Tip of the Week

Over the past couple weeks we’ve received a number of questions regarding gamepad calibration, both at FIRST and at REV Robotics, though question submitters had no idea that gamepad calibration was the issue - so let’s cover the topic!

How does a joystick know where “center” is on a gamepad? On virtually all gamepads the analog joysticks have an electrical device (usually a potentiometer) that electrically measures the motion of the stick. If the electrical device’s value at “center” does not coincide with the value the gamepad thinks should be center, the stick will have a non-zero value at its center position; this is called drift. In a video game, drift is what causes your character to walk left (or right, etc) even though you’re not moving the joystick. For a robot, this can cause ghost turning or unwanted motor or servo motion. So how is this “center” value determined?

Some gamepads, like the Sony DualSense (PS5) gamepads, internally store the value of the resistive device at its “center” position so that it knows what value is considered “center” regardless of how the stick is oriented when powered on. In order to make the gamepad reset that value, there is a small hole on the underside of the gamepad hiding a reset button, which can be used to reset the controller and account for the drift. Other gamepads, like the Logitech F310 gamepads, simply read the value of the analog joystick when it’s first powered on and assumes the sticks are always “centered” at that time. If the analog stick is NOT centered when powered on, for example if it’s upside down or resting against something that is deflecting the analog stick, the “center” value will include some amount of drift. In order to correct this, ensure the gamepad analog sticks are centered and simply unplug and reinsert the joystick's USB connector into the Driver Station Device. When reinserted, the gamepad will again read the current analog stick value as “center” and correct the drift.

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