September 26, 2011
A new design on EZ-USB will not enumerate. What are the things to be checked?
For a custom board, look first at the following signals:
XIN - is there an oscillation on this signal?
If no, check crystal specs and layout
Vcc on all power input pins (see TRM for pins)
AVcc for at least 3.0 volts and no greater than 3.6 volts
Insure there is a 1.5K ohm resistor connected to the D+ USB connector pin 3 and that it is controlled to signal the host that a device has connected.
The matching series resistor on both the D+ and D- lines from the USB connector to the EZUSB chip. This value is selected for signal quality and is normally in the range of 22 to 30 ohms.
That the reset signal is in the range of 7 to 10 msec. This period is measured from the start of valid power.
Pins TEST, TM0, TM1, C24TST and C48TST are tied according to the manual.
SCL and SDA have valid pull ups (2.2K to 10 K ohms)
For firmware loaded onto our development board, try enumeration without EEPROM so the SIE controls the VID/PID. If problems persist, please open a support case for additional assistance.