iMX8MQ USB Device Detection Issue

[sahilnayak]

Hi NXP Team,

We are facing one issue related to USB device detection.

When we did first time bring-up, we were able to detect iMX8M as device mode successfully. After doing that multiple times, we observed that after doing the power cycle quickly we weren't able to detect processor as device. 

We observed that powering the processor after some time (approx. after 20 min), we are able to detect it. After doing the regression testing on this, now we are not able to detect processor as device at all.

After further debugging, we found that 25MHz & 27MHz crystals are not initiated from processor side. Can you please help us on this?? Any checkpoints we need to do further?

Note: We have verified the complete power sequence and reset release is as expected. We are getting the 32.768kHz RTC. 

[sahilnayak]

Hi Igor,

Any update on this?

[igorpadykov]

>What can we do to re-initiate the reference clocks??

do not power cycle quickly, increase delay between cycles.

Best regards
igor

[sahilnayak]

Hi Igor,

We have already verified the power up sequence and it is as per the manual.

What can we do to re-initiate the reference clocks??

[igorpadykov]

Hi sahilnayak

>After doing that multiple times, we observed that after doing the power cycle quickly

>we weren't able to detect processor as device. 

this may be caused by wrong power-up sequence, as it assumes that processor

was fully powered down (there are no any residual voltages after previous power-down).

So power-up sequence should start when there are no any voltages left on board, all

capacitors are fully discharged. This also may explain that 25MHz & 27MHz crystals are not initiated.

Power up sequence is described in sect.3.2 Power supplies requirements and restrictions

i.MX 8M Dual / 8M QuadLite / 8M Quad Applications Processors Data Sheet for Consumer Products

Best regards
igor