The mysterious LED5 on the nrf52840 DK: What does it indicate?

[Ken58]

Hi,

Can you tell me what LED5 on the nrf52840 DK indicates?  When is it on?  When is it off?  2 observations I have made:

1. When the DK is connected to a development computer USB port and it is running a flashed program, LED5 is on almost continuously with a very short off time about once a second - really close to being on continuously.
2. When the DK is connected to a USB power port running the same flashed program, LED5 flashes rapidly.

It seems like this would be under control of the interface MCU software.

I think the development community would like a definitive answer on this.

Thanks,

Ken

[Bendik Heiskel]

Hi Ken,

LED5 is controlled by the interface MCU(IMCU). It indicates three states of the IMCU:

1. Constant rapid blinking, indicates 5V on the VBUS pin(of the IMCU) but the device is not enumerated by the computer. This is mainly an issue when a faulty or charging only USB cable is used.
2. Continuously on, the IMCU is connected to the computer and enumerated, but theres no traffic on the SWD lines.
3. "Random" blinking, traffic on the SWD lines, when programming or debugging.

 

Best regards,

Bendik

[Ken58]

Thank you very much Bendik!

Ken