LED Diagnostics

Hardware configuration

Each USG has two indicator LEDs. The colour and position of these LEDs varies between versions.

USG v0.9: Each Olimex development board has a green ‘Status’ LED near the USB connector.

USG v1.0: One orange ‘Fault’ LED is positioned next to each microcontroller (MCU). You can’t miss them when they turn on!

Normal Operation

You should see both fault LEDs flash briefly when you apply power to the USG. Under normal operation they will not turn on at any other time.

Abnormal Operation

Each microcontroller (MCU) controls one of the two fault LEDs, and a problem may occur with either or both of them. Find the problem with the help of this handy troubleshooting chart.

LED doing this…	…means this.	Try this fix:
Neither LED flashes briefly when plugged into a host	No power, damaged hardware, or unprogrammed MCU	Check your host has power. If you are using a cable, try a different cable. Did you bust the USG board? Check for hardware damage. If this is the first time you are using this USG, there may be no firmware on the MCU.
Only one LED flashes briefly when plugged into a host	Damaged hardware, or unprogrammed MCU	One LED is flashing so your board has power. part of the board may be damaged, or the corresponding MCU may be unprogrammed.
One or both LEDs stays lit when USG powered on	Incorrect firmware version	Firmware designed for a different USG hardware revision is loaded into the MCU, so check you are building from the correct Git branch. This can also be caused by loading Upstream’s firmware into the Downstream MCU, or vice versa.
One or both LEDs flash quickly (5Hz) when USG powered on	FREAKOUT self-protection mechanism is triggered at bootup	Firmware is damaged or buggy, or inter-MCU SPI link is damaged causing a failed self-test
One or both LEDs flash quickly (5Hz) while a USB device is attached	FREAKOUT self-protection mechanism is triggered at runtime	You may have a questionable USB device, but you are more likely to have found a bug in the USG firmware. Please open an issue and describe your problem!
Downstream’s LED flashes slowly (1Hz) when a USB device is attached	Unsupported device class, or weird device configuration	The USG doesn’t support this device right now. You can open an feature-request issue, and if enough people request something it may eventually be implemented :)