I'm building a USB hub with a 24MHz crystal on it. Its basically a copy of a development board, but slightly tweaked. It uses a USB2514 USB hub controller IC
However, when we connect it to the PC, It comes up as an Un-recognised device.
We've tried the obvious things like remove the upstream choke and bridging the connections & checking that the DM+ and DM- are going to the correct pin on the USB2514.
But one thing we noticed between the development board and our board is the clock signal on Crystal is not stable. Its jumping around and not staying at a constant amplitude.
We've changed the capacitors on the crystal circuit and even changed the crystal. yet problem still is there. Tracks are the same length so there shouldn't be any propagation delays.
With the amplitude of the crystal output jumping around, its bound to effect the USB hub obtaining a phase locked signal right?
Any Ideas?
However, when we connect it to the PC, It comes up as an Un-recognised device.
We've tried the obvious things like remove the upstream choke and bridging the connections & checking that the DM+ and DM- are going to the correct pin on the USB2514.
But one thing we noticed between the development board and our board is the clock signal on Crystal is not stable. Its jumping around and not staying at a constant amplitude.
We've changed the capacitors on the crystal circuit and even changed the crystal. yet problem still is there. Tracks are the same length so there shouldn't be any propagation delays.
With the amplitude of the crystal output jumping around, its bound to effect the USB hub obtaining a phase locked signal right?
Any Ideas?
