# TUSB2046B hub with raspberry pi zero

I'm using a TUSB2046B hub connected to a raspberry pi zero. The hub circuit looks like this:

There appears to be a 12MHz sine wave coming from the crystal (as counted by my scope) and 3.3V on the VCC, /EXTMEM and EEDATA pins. If I connect a device to the Pi using a USB OTG micro-to-micro cable, lsusb shows the device. But if I connect the hub shown in the diagram, it shows nothing. And I don't see any signalling on the USBDM / USBDP lines when I inspect them with the scope.

Have I got something seriously wrong? Is there some good reason it's not talking back to me?

• What is the DC voltage on the DP/DM lines? A connected (full/high speed) device should pull DP to about 3.3V when the bus is idle. Jun 20, 2018 at 13:52
• Both lines are at approx 0V when idle. The data sheet for the TUSB2046B shows the DP line pulled to 3.3V through 1.5k-ohm, but other users of the same device (eg openhardwarecoza.wordpress.com/2015/12/07/…) don't even bother with the isolation resistors - they just wire DP and DM directly to the Pi's USB port.
– Tom
Jun 20, 2018 at 14:43
• Just try to connect a 1k5 resistor from USBDP to the 3.3V source for testing. It is possible that the chip behaves differently in self powered vs. bus powered mode. Jun 20, 2018 at 15:28
• I'll have a go and report back.
– Tom
Jun 20, 2018 at 15:45
• Do you mean TUSB2046B full-speed hub from Texas Instruments, right? Jun 21, 2018 at 0:26