[WP76xx][HW] Switch USB host or USB function

Legato Linux distribution (Yocto project)
1

WP76xx_switch_USBHost_function.xlsx (39.9 KB)

Back Ground:
We would like to switch the function that WP76xx was operated as USB host or USB function.
In order to support it, we make the attached block diagram.

  • How to switch: control GPIO22 and GPIO23, and supply to power SW IC to supply Micro USB IF
  • How to recognize function: Check the logic via USB_ID or GPIO25

Question:
Please check the attached file as “WP76xx_switch_USBHost_function.xlsx”.
Can this block diagram support to switch either USB Host or USB Function?

Best Regards,

2

for hardware topic, please directly contact Sierra FAE.

3

Are we talking about USB OTG?

4

Hi, Jordan

Are we talking about USB OTG?

No, I talked the following behavior that;

  • USB Host: WP76xx supply voltage to external USB device
  • USB function: No supply voltage, only receiving data via USB
5

OK, I see. Then it needs a help from the HW team.

6

Hi Hiroki,
Please make SFDC ticket for this.

7

Hi, Sierra Team

As we talked with customer, they consider to switch USB function or Host as I said.
In that case, they consider that is judged USB function or USB Host by trigger the logic of USB_ID.

  • USB_ID: “H” or Open —> WP760x=USB Host (Supply USB_VBUS to external USB device)
  • USB_ID: “L” —> WP760x=USB function (Receive USB_VBUS from external USB device)

Question:
Do you have the way how to monitor the logic of USB_ID either “H” or “L” in legato App or Linux command?
(Sorry I could not find legato.io.)

8

do you know what device will be plugged to the USB?
If yes, you can check “cat /sys/kernel/debug/usb/devices” for the device name.

9

do you know what device will be plugged to the USB?

No, I could not confirm device name.

I consider the following sequence to switch USB host/function.

[1] Monitor USB_ID “H” or “L”, instead of GPIO
(Because our system is insufficient GPIO IF.)
[2] If USB_ID=“H”, WP76xx set to be worked as USB function
[3] If USB_ID=“L”, WP76xx set to be worked as USB Host

In order to fulfill [1], I would like to know whether USB_ID can be monitored either “H” logic or “L” logic under legato or yocto framework.

10

how about checking the kernel log?
I saw that in case of USB host, when client connected, you should see this message in dmesg:
“New USB device found”.

11

how about checking the kernel log?

Thanks for your advise, but it could not be applied in our system.
Because I consider that WP76xx will be switch either USB Host or USB Function before external USB device is jack-in.
So I consider the way to switch USB Host/Function, and I assume that switching USB can be monitored USB_ID logic.
That’s why, I asked it.

12

Please contact Sierra FAE as this is more likely to be hardware stuff.