11. Troubleshooting

Symptom	Cause	Remedy
No life at all with 24 V connected	The button; the supply; a reversed XT30	Check the supply's output, the JST button cable, the XT30 polarity. A reversed supply has usually destroyed the board
The board is on but cannot be switched off	3.3 V on the programming header	Unplug the ST-Link or adapter
The board turns on when the supply is connected	The same, or a motor was turned by hand	Unplug the programmer; move an unpowered robot slowly
The test firmware's report at power-on says Connection is: BAD for a joint	Not seated; dead; wrong orientation	Power off, check the orientation against the DIAG pins, reseat. A driver that was powered the wrong way round is dead, and the board may be too
A motor hums but does not turn	A phase open; a motor wire loose in the terminal	Check the four wires of that joint's cable
A motor turns the wrong way	Normal for a new build	Flip direction_reversed in the main firmware
A switch does not show in #LIMIT	Wiring; the switch; the wrong terminal	Check 24 V to the switch and the signal wire; try the other terminals to find which input changes
An inductive sensor never triggers	Gap; no 24 V; the sensor is PNP	NPN NO sensors only; brown 24 V, blue GND, black signal; gap of a millimetre or two
The E-stop reads pressed with the button released	Wiring open; the button is NO	NC contact between the E-stop terminals
The drivers are hot and shut down	The fan	The fan must run; 5 V, not PWM
No serial port on the PC	The board has no power; the cable; the driver (Windows)	The board enumerates only when powered; try another cable and port
The main firmware does not upload	ST-Link driver; the adapter; the target not powered	Install STSW-LINK009; check the adapter's 3.3 V; disconnect the 24 V supply

For anything the firmware reports to the PC, the robot-side pages apply: Troubleshooting in the Robot Manual.

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