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Problem with VBUS pin of the USB OTG PHY of PMU TPS65950

Naïc
Prodigy 80 points
Other Parts Discussed in Thread: TPS65950, DM3730

Hi,

We are designing a board with the DM3730 with the PMU TPS65950, and we want to use a USB/Ethernet HUB on the OTG USB port via the PHY integrated inside the TPS65950.

We have an issue with it and we think that the problem is due to the VBUS pin that we have let disconnected. 

The error message is :

ubuntu@omap:~$ dmesg | grep -i musb
[    0.127624] musb-hdrc: version 6.0, pio, host, debug=2
[    0.127929] musb-hdrc: ConfigData=0xde (UTMI-8, dyn FIFOs, bulk combine, bulk split, HB-ISO Rx, HB-ISO Tx, SoftConn)
[    0.127960] musb-hdrc: MHDRC RTL version 1.800
[    0.127960] musb-hdrc: setup fifo_mode 5
[    0.127990] musb-hdrc: 28/31 max ep, 8192/16384 memory
[    0.127990] musb_core_init 1515: musb-hdrc: hw_ep 0shared, max 64
[    0.128021] musb_core_init 1515: musb-hdrc: hw_ep 1tx, max 512
[    0.128051] musb_core_init 1524: musb-hdrc: hw_ep 1rx, max 512
[    0.128051] musb_core_init 1515: musb-hdrc: hw_ep 2tx, max 512
[    0.128082] musb_core_init 1524: musb-hdrc: hw_ep 2rx, max 512
[    0.128082] musb_core_init 1515: musb-hdrc: hw_ep 3tx, max 512
[    0.128112] musb_core_init 1524: musb-hdrc: hw_ep 3rx, max 512
[    0.128143] musb_core_init 1515: musb-hdrc: hw_ep 4tx, max 512
[    0.128143] musb_core_init 1524: musb-hdrc: hw_ep 4rx, max 512
[    0.128173] musb_core_init 1515: musb-hdrc: hw_ep 5tx, max 512
[    0.128173] musb_core_init 1524: musb-hdrc: hw_ep 5rx, max 512
[    0.128204] musb_core_init 1515: musb-hdrc: hw_ep 6tx, max 32
[    0.128204] musb_core_init 1524: musb-hdrc: hw_ep 6rx, max 32
[    0.128234] musb_core_init 1515: musb-hdrc: hw_ep 7tx, max 32
[    0.128234] musb_core_init 1524: musb-hdrc: hw_ep 7rx, max 32
[    0.128265] musb_core_init 1515: musb-hdrc: hw_ep 8tx, max 32
[    0.128295] musb_core_init 1524: musb-hdrc: hw_ep 8rx, max 32
[    0.128295] musb_core_init 1515: musb-hdrc: hw_ep 9tx, max 32
[    0.128326] musb_core_init 1524: musb-hdrc: hw_ep 9rx, max 32
[    0.128326] musb_core_init 1515: musb-hdrc: hw_ep 10tx, max 32
[    0.128356] musb_core_init 1524: musb-hdrc: hw_ep 10rx, max 32
[    0.128356] musb_core_init 1515: musb-hdrc: hw_ep 11tx, max 32
[    0.128387] musb_core_init 1524: musb-hdrc: hw_ep 11rx, max 32
[    0.128417] musb_core_init 1515: musb-hdrc: hw_ep 12tx, max 32
[    0.128417] musb_core_init 1524: musb-hdrc: hw_ep 12rx, max 32
[    0.128448] musb_core_init 1515: musb-hdrc: hw_ep 13shared, max 512
[    0.128448] musb_core_init 1515: musb-hdrc: hw_ep 14shared, max 1024
[    0.128479] musb_core_init 1515: musb-hdrc: hw_ep 15shared, max 1024
[    0.128540] musb-hdrc musb-hdrc: MUSB HDRC host driver
[    0.128570] musb-hdrc musb-hdrc: new USB bus registered, assigned bus number 1
[    0.128875] usb usb1: Product: MUSB HDRC host driver
[    0.128906] usb usb1: Manufacturer: Linux 2.6.39.3.klk musb-hcd
[    0.128967] usb usb1: SerialNumber: musb-hdrc
[    0.130004] musb_start 939: <== devctl 80
[    0.130279] musb_init_controller 2083: HOST mode, status 0, devctl 81 B
[    0.130401] musb-hdrc musb-hdrc: USB Host mode controller at fa0ab000 using PIO, IRQ 92
[    0.282470] musb_stage0_irq 625: VBUS_ERROR in a_idle (80, <SessEnd), retry #0, port1 00000100
[    0.282501] omap2430_musb_set_vbus 199: VBUS b_idle, devctl 80

This means that the CPU doesn't switch to the host mode. For information, the ID pin is connected to GND.

Does the reason of this issue is really the VBUS pin disconnected ?

How does this pin have to be connected ? With a capacitor to GND ?

Is there a software workaround because in our design this pin isn't reachable ?

 

Thank you in advance for response.

  • 0
    Prodigy 80 points

    Hi,

    We can confirm now that the issue was exactly due to the VBUS level.

    We have found a hardware workaround to this problem by connecting the CP.CAPM pin to +5V via a 100ohms resistor (to avoid damages...). By this way, the CPU is in host mode.

    Now, we know that the VBUS pin has to be permanently connected to +5V when you want to be in host mode on the OTG USB bus like in our case.

    It wasn't so easy to find this information, as for the connection of the ID pin. Maybe it would have been interesting to make an application note with the different ways to connect the OTG USB bus in different case of use...

     

  • 0 in reply to Naïc
    Prodigy 250 points

    Could you please share your schematic portion showing OTG interface?

    Actually, we are also facing VBUS error when we connect Linksys USB300 Ethernet module on it.  We have connected VBUS pin of TPS65950 with USB OTG connector's pin1 by keeping ferrite bead near to usb pin.1.

    Regards,

    Kartik Gandhi