What exactly does the LED above the Reset button mean. I see it flashes upon a power-up and it also flashes during USB communications with the PC (during programming and when sending data to the PC).
Anyone? Also, is there a way to turn off the LED to conserve power?
The LED is the Status LED; see Getting Started - Downloading a Program in the Handbook.
It is used to indicate the mbed has power, and flashes to show activity such as saving files on to the mbed, downloading a program in to the microcontroller internal FLASH after hitting reset, and on any serial activity between the mbed and the PC.
We don't currently have a way to turn the LED off, and to be honest, the power saving by turning it off will actually be negligible at the moment compared to the other things on the board. We might do some experiments in the future to see if we can do a low power mode for the interface, so i'll make a note of the idea of being able to disable the LED too.
Is there any new information available since last year? I also want to disable status LED. More due to the unit must be completely dark, than power saving. It would be handy with disable option for status LED. I might end up removing the status LED physically.
If you need to conserve more power ... try blinking the led instead of steady light. :) Just send some dummy bytes on the com. But with eth phy powered .. this blinking led is a joke.
If the unit must be completely dark ... another way is to put something like a sticker above it.
You could take a look at:
It enables a powerdown mode, which means the interface can be turned off when powered externally (but will still be on when connected to USB)
Here is a mod you could try: connect the junction of LED1 and R3 to ground. This will prevent the LED from lighting. It will burn a constant 15mA from the 3.3V supply, which should not be a problem.
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