FRDM-LS1012A USB gadget mode does not work

[bensonpeter]

Hi everyone,

I am working on a project with the FRDM-LS1012A development board. I need it's USB 3.0 port to work in USB gadget mode(I need FRDM-LS1012A to appear as an RNDIS ethernet interface on a host PC). And it does work fine when an external power supply is connected to USB 3.0 PWR header. Without external power, PC does not detect it(nothing on dmesg). But shouldn't it work this way as it is a USB gadget device whose VBUS is driven by host PC?

On doing some further research on this issue, I've found that the external power is not required continuously i.e., once the interface is detected by the host PC, the external power can be removed and the board will continue to work).

USB1_SW_PWRFAULT_B pin stays low until an external power supply is connected. But I wonder what causes the fault in the first place.

From board schematics, I can see that external 5V bus is connected to ENRESET pin of MAX8586. i.e., the board will recover from any faults only if an external 5V bus is connected. I think this causes the board to recover from this unknown fault and work properly when an external power supply is connected.

Is there any way to do this without external 5V supply? Please guide me. 

Thanks in advance

[Pavel]

The FRDM-LS1012a was not developed for using as USB gadget. If this board will be used as USB gadget, the USB CMSIS DAP connector can be used as power supply.

See the Figure 2-1 of the FRDM-LS1012a Reference Manual:

https://www.nxp.com/webapp/Download?colCode=FRDM-LS1012ARM

Have a great day,
Pavel Chubakov

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[bensonpeter]

Thanks Pavel for the answer though it did not answer my question.

FRDM-LS1012A does work as USB gadget for me. The only issue I have on this is that it needs an external power supply connected to USB 3.0 PWR header. Is there any way to get this done without the external power supply?

(Of course, my board is powered from USB CMSIS DAP connector as it is the only source of power to LS1012A and every peripheral on the board other than that USB 3.0 port).