Is the miniPCIe on the RK3399 "real" PCIe?

mikaelm · Posted at 3/27/2017 17:29:11

Hi!

Is the miniPCIe on the RK3399 "real" PCIe?

As in, can I plug in *any* form of miniPCIe device into it, such as for instance, a miniPCIe gigabith ethernet card?

A detail question: How do you do the PCIe switching on your RK3399 board, to convert the 4-lane PCIe interface on the RK3399, to a 2-lane PCIe interface (via M.2) and a 1-lane PCIe interface (via miniPCIe)? The last (fourth) lane, do you use it for anything?

Thanks!

leung先森 · Posted at 3/27/2017 18:59:57

It can be used for any M.2 device theoretically, but need the kernel support .

KD0OHR · Posted at 4/9/2017 15:44:18

Last edited by KD0OHR In 4/9/2017 15:45 Editor

The MiniPCIe connector on the RK3399 board has only USB connected. All 4 lanes go to the M.2!

This is acceptable for wireless modules but not for your purposes. The m.2 port is the only port on this board with PCIe, and the PCI SIG spec says hosts with a "B" (or "socket 2") can provide PCI 2x and one sata so finding an adapter that will do what you want will be a challenge without some custom fab work. The device does have 4 pairs tx and 4 pairs rx PCI lanes going to it though so if whatever you plug in has a 4x PCI PHY instead of an SATA PHY(like the m.2 sata adapter sold here), AND everything is wired the (unsupported) way theoretically it could be connected so long as you have A.) powered the device properly and B.) Kernel support as mentioned by Leung.

Now, this being said, I'm attempting to connect a graphics card to the RK3399 M.2 port 2x with a P14S-P14FP (M.2 (NGFF) to PCIe X2 Edge Extender Board)

and I have not had success. I can't even find the card on the I2C bus (SMBus) let alone install linux drivers for it at this point. We're getting into somewhat uncharted territory attempting to arbitrarily use interfaces for unintended purposes, maybe in time people will document such activities better, but for now it's us blazing the trails it would seem ;)

KD0OHR · Posted at 4/15/2017 09:58:58

Last edited by KD0OHR In 4/15/2017 13:07 Editor

Further information:

Power requirements for the PCIe Bus are attached in an image but its up to 12V@5.5A, 3.3v@3A needs to be supplied by the PCIe Slot to your device. 3.3v could be used as the RK3399 datasheet says the SY8113BADC outputs 3.3v@3A, though might need to be disconnected from the M.2 port on your RK3399 and an external supply used for loads other than an M.2 SSD.

PCIe 6 pin power connector 75W or 12v@6.25A
PCIe 8 pin power connector 150W or 12v@12.5A