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TPS2541: Can read from a USB Stick but cannot enumerate an iPad

Matt Barclay
Prodigy 30 points
Part Number: TPS2541
Other Parts Discussed in Thread: TUSB211

We have a hardware design using the TPS2541.  The CTRL pins are all pulled high.  I am using a modified USB cable to connect from a port on my laptop to our hardware.  Only the data pins from the USB cable are connected to my board.

I can plug USB thumb drives in and they work fine.  But when I plug in an iPad, I get errors like this on the Linux host:

[445629.280650] usb 3-3: new high-speed USB device number 71 using xhci_hcd
[445629.400744] usb 3-3: Device not responding to setup address.
[445629.612731] usb 3-3: Device not responding to setup address.
[445629.820602] usb 3-3: device not accepting address 71, error -71

I'm not sure what could be going wrong here.

  • 0
    TI__Mastermind 42795 points

    Just to confirm, the TPS2541 DP_OUT/DM_OUT (upstream) pins on your board connect to the laptop and the TPS2541 DP_IN/DM_IN (downstream) pins connect to the iPad or USB stick? Are you powering the iPad through the TPS2541 power switch (from IN to OUT pins)? What is the capacity of the 5V power source (is it enough to power the iPad?)? You might try monitoring the voltage to the iPad to make sure it remains stable during communication to the USB host.

  • 0 in reply to Eric Wright
    Prodigy 30 points
    Correct, the DP_OUT/DM_OUT go to the Host (laptop), and the DP/DM IN go to the iPad.

    I made a new (shorter) cable connecting my Laptop to the TPS2541 and it has been much more reliable. I am able to communicate with the iPad. I'm worried though that the USB signal is marginal to my laptop. Would a TUSB211 help improve the signal?