The U6 has two LEDs to provide feedback about power and operational status.
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Power LED (Yellow): Connected directly to the VS rail via a series resistor.
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Indication: A lit LED confirms that voltage is present on the VS line.
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Note: This is a hardware-only indicator; it does not verify if the voltage level is within the valid operating range or if the processor is active.
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Status LED (Green): Managed by the device's main processor to provide functional feedback.
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Behavior:
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Startup: Flashes immediately upon reset and during the USB enumeration process. When the USB cable is connected to the U6, the Status LED should blink a few times and then remain solid on.
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Ready: Remains solid green once enumeration is successful.
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Activity: Blinks or "flickers" to indicate active USB communication traffic.
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LED blinking continuously at about 4 Hz (when no software is running): This indicates that the U6 is in flash mode. See Section 1.2 and reprogram the device.
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Other or no Status LED behavior, even with no connections besides USB: Try using the different jumpers and reprogramming as described in Section 1.2. If you get no LED activity with any jumpers, but know the USB port is good and providing 5 volts, the device is likely damaged beyond the possibility of field repair. If your device is unresponsive, Contact us, or start an RMA here: returns, exchanges, and repairs. Also see item F in the USB Communication Failure App Note.