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Troubleshooting

Common problems and what to check. Solutions here stay at the "what to look at" level — working through the problem yourself is part of the learning.

The program won't compile

What you see: make fails and prints error messages.

What to do:

  1. Read the first error message — later errors are often caused by the first one.
  2. Find the file name and line number in the error message (e.g., joystick.c:14:).
  3. Open that file in Geany and look at that line number.
  4. Common culprits: missing ; at the end of a statement, unmatched { or }, a misspelled function or variable name.

→ Reading error messages

"Permission denied" when running

What you see: ./motor: Permission denied or similar.

What to do: Try prefixing the command with sudo:

sudo ./motor

Some programs that control GPIO pins require administrator permissions. Your handout will say which programs need sudo — follow it exactly.

Motor doesn't spin

What to check:

  1. Power supply — Is the battery connected to the power supply board? Is the power supply switch on?
  2. Wiring — Do your wires match the wiring diagram exactly? Check the L293 chip's orientation (the divot).
  3. Pin modes — Did you call pinMode() for all three motor pins in setup()? If a pin is not configured, pwmWrite() and digitalWrite() will have no effect.
  4. Direction pins — Are L293_INPUT1 and L293_INPUT2 set to opposite values? If both are HIGH or both are LOW, the motor brakes instead of spinning. → The motor driver
  5. Enable pin — Is L293_ENABLE set to a non-zero value with pwmWrite()? A value of 0 means no power to the motor.

Joystick reads garbage or one axis is stuck

What to check:

  1. Wiring — Recheck the MCP3008 wiring against the diagram. One crossed wire is enough to break a channel.
  2. Chip orientation — Is the MCP3008's divot facing the correct direction?
  3. Wrong channel — Are you reading the correct ADC channel for the axis? X_INPUT (100) is the X axis. If Y always reads 0 and you want Y, you need to find the Y channel from the wiring diagram and read that instead.

→ analogRead()

Camera window doesn't open (Lab 4)

What to check:

  1. Webcam plugged in? — Make sure the USB camera is connected before you run ./ai-motor.
  2. Give it a few seconds — The model takes a moment to load. Wait 5–10 seconds after running before you decide something is wrong.
  3. Run as a regular user — ai-motor should typically be run without sudo unless your handout says otherwise. Try both and see.

git reset --hard didn't fix it

git reset --hard only restores tracked files to the last committed version. If you accidentally deleted a file rather than edited it, or if you are outside the hotis-projects-starter directory, it may not behave as expected.

Make sure you are in hotis-projects-starter:

cd hotis-projects-starter
git reset --hard

→ Resetting your work

Something else is wrong

Ask your instructor. Describe what you tried, what you expected to happen, and what actually happened. Describing a problem out loud often helps you notice the answer yourself.