I'm trying to design a breakout board and connect the Google coral chip to my Toradex Colibri imx6 SoC via usb. I'm assuming that the imx6 is using 3v3 logic because it doesn't indicate otherwise, and everything I've connected to it via usb thus far works fine. The datasheet of the Coral Edge TPU says that their USB operates on 1.8V. Do I need to account for this somehow in my design by using a logic level shifter to my schematic? I don't even really know if USB operates at 3.3v logic level either I'm just confused about why they would say that in the datasheet.

I've searched for USB logic level shifters and I haven't found anything, so I feel like I'm missing something basic. I have a logic level shifter for the GPIO pins on a side note and those aren't differential so that's fine.

Coral Edge TPU datasheet is in the Documentation section of this link: https://www.coral.ai/products/accelerator-module

Colibri IMX6 datasheet on page 30 talks about their USB connections: https://docs.toradex.com/102075-colibri-imx6-datasheet.pdf

Thanks for any help.

  • 1
    \$\begingroup\$ Can you point what part of the datasheet says their USB works on 1.8V? \$\endgroup\$
    – Justme
    Jun 8 '21 at 15:15
  • \$\begingroup\$ All USB data signals are 3.3V, all USB VBUS are 5V. There are no other levels possible so no one makes level shifters. You may have a USB chip powered by 1.8V only if it has an internal voltage boost circuit. \$\endgroup\$
    – Ben Voigt
    Jun 8 '21 at 15:40
  • \$\begingroup\$ Anyway your Coral module is powered from 3.3V \$\endgroup\$
    – Ben Voigt
    Jun 8 '21 at 15:41
  • \$\begingroup\$ Justme - On page 8 there's a table of pins and what they're for; rows 13 and 14 are USB, 4th column shows 1.8V. \$\endgroup\$ Jun 8 '21 at 17:17
  • \$\begingroup\$ Yeah I think you guys are correct, I think it will be fine. I looked at the datasheet again and the min max voltages it can tolerate includes 3.3V so it should work fine. \$\endgroup\$ Jun 9 '21 at 18:12

If it's using USB, you shouldn't need any voltage level translation, because USB itself requires specific voltage levels and if the device can't output or input those voltage levels it can't claim it's using USB. At least not without getting in trouble with the USB-IF.


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