Hi,
We are using a TUSB2046BIVFR on a board of ours. The first 200 boards worked flawlessly, however, we have a new board that is showing one or TWO child device being configured on the HUB with PID/VID of 0x0000. We have (2) unused ports (DM/P3 and DM/P4). If we are NOT using a port on the hub, is it okay to just leave the port pins unconnected, or should we have had pull down 1.5k resistors?
Debug I have attempted on just this board:
- Replaced crystal, load crystals, etc.
- Replaced inline caps, or parallel caps
- Replaced device
- Xrayed PCB
Very strange. I have a VERY simple implementation of this device. Anyone have any recommendations? How should the device respond if that last (2) ports are unconnected?
More details: The first port is connected to an FTDI chip, that converts a UART to USB. This port ALWAYS works, so I know the device is somewhat happy. The 2nd port is connected to an AVR micro controller. This port is NOT working. I have replaced the AVR as well, and it's running perfectly, but USB is broken. I removed this device from the TUSB2046 by removing the inline resistors, and the 1 or 2 phantom unknown USB devices still show up. This circuit has worked on all other boards. The 3rd and 4th port are occasionally configuring in Windows or Linux as "unknown" devices. They are no connects.
All other boards produced are fine, so I'm assuming it's a manufacturing flaw on the PCB, but where could it be? I've sampled all pins, and all levels look good. Data lines look clean.
Scratching my head.
Garrick
