Hello there,
I need your help as I am not able to get the TUSB2036 device working at all. It gets not detected by any host PC (have tried Linux and Windows machines). It behaves like connecing a USB charger or power bank: Power gets supplied to the board but nothing else happens. The device seems to be hanging in its startup sequence as the DP0PUR pin never gets driven high. When patching the upstream D+ to 3.3V using a pull up the PC recognizes a full speed device, but fails to access the USB registers.
The configuration is as follows (see with respect to the attached schematics):
The USB hub gets powered by BUS. The 5V-To-3.3V converter is inside the CP2105 (U23) downstream device which serves power for the HUB. 1uF and 4.7uF capacitors are placed closely to the CP2105 power output. TUSB2036 is located in 2 cm distance from that chip on the PCB.
USB hub port 1 is embedded connected to the above full speed device CP2105 (U23)
USB hub port 2 is embedded connected to a full speed USB Microcontroller that has a different power domain. It is possible that this devices powers on and off while the hub is operating. It is most likely that this device is not powered when connecting the HUB to a Host PC. Is is also possible that the downstream device is powered prior than the HUB.
USB hub port 3 is not connected
Device configuration is as follows:
Mode = High for Oscillator operation
NPINT[1...0] = 01 (Port1 is permanently connected (CP2105) and Port2 is externally attached)
EXTMEM = 1 (No external Memory)
GANGED = 0 (No power management)
NP3 = 1 (Port3 not used)
Reset is connected to a RC chain.
What I have already checked is:
- 3.3V power supply ripple looks good
- Clock is 48 MHz and signal looks good. (See attached picure)
- Reset signal seems to be okay and asserts 50-100 ms after the clock starts (See attached picure)
- USB connector pinout is validated and works in several other designs.
- The clamp diode (U22) bypass capacitors (C66, C65) have been removed.
- The downstream devices are operational as I have tested them seperatly using patch wires to the USB upstream port connector.
- I have also changed the TUSB2036 chip several times against new ones
I think the issue should be something simple that I am to blind for to see. Maybe you guys have some ideas that I can check for :) Thank you in advance.
Best Regards
Martin
