Derek Molloy wrote up this useful tutorial on how to control the BeagleBone Black on-board LEDs using Java.
One of the first things you would like to do when you connect to the Beaglebone Black is see that you are having an impact on the hardware. In this short post I am going to look at how you can change the behaviour of the Beaglebone on-board LEDs – the four (blue on the BBB) LEDs in the corner near the reset button.
Now, the LEDs are there for a reason, and that reason is to give information about the Beaglebone state (from beaglebone.org):
USR0 is configured at boot to blink in a heartbeat pattern
USR1 is configured at boot to light during microSD card accesses
USR2 is configured at boot to light during CPU activity
USR3 is configured at boot to light during eMMC accesses
We can change the behaviour of these LEDs, but obviously we will temporarily lose this valuable information. The heartbeat tells you that the BBB is alive, which is always useful to know. The others are fairly self explanatory (the eMMC is the solid state memory that you are booting from).
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