We are having trouble getting our embedded hub design to function correctly. The design is meant to be used as an internal two port hub with one port always attached to a touch panel and the second an external slow speed device.
The schematics below have several errors that we have fixed:
- DP/DM swapped
- 48mhz crystal changed to 6mhz
- R1/R2 removed
- BUSPWR pulled high
- MODE pulled low
With these errors fixed and the board plugged into a windows PC, we get errors retrieving the device descriptor. A linux PC showed the same error.
The crystal only starts up when the device is plugged into the PC, then shuts off after a second or so (and the device has failed). We captured the USB trace on a cheap analyzer:
First group looks ok:
second does not:
We also noted that our crystal circuit does not have a 1.5K series resistor as in the EVM, but the signal levels look good at the IC.
Reset is generated by a voltage monitor - MAX811SEUS (140ms delay after VCC > 2.93V)
Any thoughts why this hub doesn't function properly would be appreciated.
Thanks!
