AnsweredAssumed Answered

FRDM-LS1012A USB gadget mode does not work

Question asked by Benson Peter on Apr 16, 2018
Latest reply on Apr 17, 2018 by Benson Peter

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