LabVIEW FRC 2015: Safety Configuration Tutorial

For FRC 2010 and earlier, the Watchdog timer was used as a safety mechanism to prevent runaway

robots. LabVIEW FRC 2011 introduced a new way to implement similar functionality for MotorControl,

PWM, Relay, RobotDrive, and Solenoid operations with the Safety Configuration VIs. These safety

configuration VI’s are unchanged for newer versions of LabVIEW FRC, including LabVIEW FRC 2015.

There are three main steps to using the safety features:

1. Opening a new reference to a MotorControl, PWM, Relay, RobotDrive, or Solenoid creates a

“safety reference” for that device in the background.

2. Calling the Safety Config VI for the device allows you to enable or disable the safety feature for

that device and to set a timeout value.

3. The value written to that device must be updated at least every period of the timeout counter

or the safety mechanism will interrupt its output. The following actions are taken for each type

of device:

MotorControl – stops the motor

PWM – turns off PWM

Relay – resets the relay to its default value

RobotDrive – stops the motor

Solenoid – resets the solenoid to its default value

NOTE: Only the RobotDrive Open VIs enable the safety feature by default. For other devices, the safety

feature needs to be manually enabled by calling the Safety Config VI for that device.

Here is an example of the Safety Config VI being used for MotorControl:

When the MotorControlSafety VI is called it automatically creates a “safety reference” for that device in

the background. The MotorControlSafetyConfig VI is then used to enable the safety feature and set a

timeout value of 100ms. Inside the While Loop, the MotorControlSetOutput VI is called repeatedly. If

more than 100ms elapse between calls to the MotorControlSetOutput VI then the motor will be stopped

until the MotorControlSetOutput VI is called again. At the end of the program, calling the

MotorControlClose VI also closes the “safety reference” in the background.

For safety reasons it is recommended that you always enable the safety feature for your MotorControl,

PWM, Relay, RobotDrive, and Solenoid devices. However, if you prefer to use the Watchdog VIs to

implement a safety mechanism in your code, those are also still available to you in the newer versions

of LabVIEW FRC.