I am trying to gather some info about the M.2 connector.

My end goal is to add Wifi capabilities (e.g. using an Intel Pro Wireless M.2 card) to a Computer On Module system (iMX6, raspberry pi cm3, etc.).

I've been looking on Wikipedia and Google for info about M.2 connectors and all I have found is that M.2 connectors have different capabilities depending of the physical keying. And that Intel Pro Wireless cards use PCIe and USB bus (also some seem to use UART).

Is there somewhere a document giving the pin layout of the M.2 connector, in particular for A-E keyed cards?

Do the M.2 host must provide USB and PCIe or is it USB or PCIe ?


1 Answer 1


The M.2 connector is defined with great flexibility, almost to the point that the moniker "M.2" (formerly NGFF - Next Generation Form Factor) being useless. They define at least 12 different notch-based configurations, from A to M, which defines different mix of interfaces, see page 9 of this presentation.

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In the mix there could be anything, USB2, USB3, SATA, PCIe, UART, I2C, DisplayPort, you name it, not just OR or AND.

However, from the eclectic mix of interfaces in each particular list it must be concluded with confidence that the host may supply only a subset of interfaces per a given M.2 notch. For example, the SSIC is not there yet (and might never be there), and the audio or "UIM" might be not in the list of SoC ports. So it is up to system designer which interface to provide.

  • \$\begingroup\$ I already know that depending on the keying the available networks can change. However, there must be some kind of standard for the pinout, or people would not be able to choose which card vendor they choose for a given M.2 host. For instance, all A keyed M.2 cards must expect to be connected to have USB 2.0 interface on the same pins. \$\endgroup\$
    – Benjamin T
    Sep 29, 2017 at 19:49
  • \$\begingroup\$ The AND or OR part was more for Intel PRO Wireless cards, the available datasheets just says "PCIe, USB" without saying if both are required at the same time and for what purpose. I was hoping that having the M.2 pinouts for those cards could give me the start of an answer (e.g if USB and PCIe use the same pins). \$\endgroup\$
    – Benjamin T
    Sep 29, 2017 at 19:49
  • \$\begingroup\$ @BenjaminT, if you are looking at M.2 from a modem card perspective, I can assure you that the interface is "OR". For modems it could be one of the interfaces, SSIC, HSIC, USB2, USB3, or PCIe, it depends on what a host S/W developer has mastered to make, and which of modem's interfaces is ready. Only one interface is required, they are mutually exclusive at application interface level. \$\endgroup\$ Sep 29, 2017 at 20:47
  • 1
    \$\begingroup\$ @BenjaminT is the card you have Wi-Fi + Bluetooth? If so usually the BT uses USB and the Wi-Fi uses PCIe - hence it lists both. \$\endgroup\$ Sep 29, 2017 at 21:12

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