Programming · Common Code Mistakes
Fix the classic FTC code pitfalls
Avoid blocking, missing waits, encoder misuse, and bad init that burn matches.
What this is
- Checklist of frequent code errors that break robots.
- Why they happen and how to prevent them.
- Quick tests to catch them before events.
When you need it
- New programmers joining mid-season.
- Robot freezes, won’t start, or ignores inputs.
- Autos or TeleOps behave differently in matches vs practice.
How it works
- Blocking loops: avoid while-loops in LinearOpMode without yields; use
opModeIsActive()and small sleeps. waitForStart(): always call before main loop; avoid work that drives motors before start.- Encoders: reset when needed; keep consistent direction; convert ticks↔distance correctly.
- Init: hardwareMap names must match config; guard sensors that may be absent; handle nulls.
Common mistakes
- Infinite loops without
opModeIsActive()checks. - Driving motors before start in init loop.
- Wrong ticks-per-rev or wheel diameter causing drift.
- Forgetting to set motor direction or zero power behavior.
How to test it
- Step through auto with low power; verify loop exits when
!opModeIsActive(). - Check motor power is zero before start; watch telemetry in init.
- Drive a measured distance and compare ticks to expected.
- Toggle zero power behavior (BRAKE/COAST) and confirm expected motion.
Related problems
- Robot won’t stop → missing
opModeIsActive()checks or timeouts. - Strange headings → mixed motor directions or encoder signs.
- Start-line penalties → motors moving during init; ensure powers zeroed.