Telemetry: Recording and Sending Real-Time Data
Telemetry (literally “measuring remotely”) is the process of recording and sending real-time data about the performance of your robot to a real-time readout or log file. Recording and viewing telemetry data is a crucial part of the engineering process - accurate telemetry data helps you tune your robot to perform optimally, and is indispensable for debugging your robot when it fails to perform as expected.
By default, no telemetry data is recorded (saved) on the robot. However, recording data on the robot can provide benefits over recording on a dashboard, namely that more data can be recorded (there are no bandwidth limitations), and all the recorded data can be very accurately timestamped. WPILib has integrated support for on-robot recording of telemetry data via the
DataLog classes and provides a tool for downloading data log files and converting them to CSV.
In addition to on-robot recording of telemetry data, teams can record their telemetry data on their driver station computer with Shuffleboard recordings.
Adding Telemetry to Robot Code
WPILib supports several different ways to record and send telemetry data from robot code.
At the most basic level, the Riolog provides support for viewing print statements from robot code. This is useful for on-the-fly debugging of problematic code, but does not scale as console interfaces are not suitable for rich data streams.
WPILib supports several dashboards that allow users to more easily send rich telemetry data to the driver-station computer. All WPILib dashboards communicate with the NetworkTables protocol, and so they are to some degree interoperable (telemetry logged with one dashboard will be visible on the others, but the specific widgets/formatting will generally not be compatible). NetworkTables (and thus WPILib all dashboards) currently support the following data types:
Telemetry data can be sent to a WPILib dashboard using an associated WPILib method (for more details, see the documentation for the individual dashboard in question), or by directly publishing to NetworkTables.
While NetworkTables does not yet support serialization of complex data types (this is tentatively scheduled for 2023), mutable types from user code can be easily extended to interface directly with WPILib dashboards via the
Sendable interface, whose usage is described in the next article.