PCIe x1 on Jetson TX2 evaluation board


We are trying to communicate with an FPGA evaluation board which is installed on the PCIe extension connector on the Jetson TX2 evaluation board.

When the FPGA is configured to PCIe x4 the FPGA is detected by the Jetson on every power on cycle (running lspci on the terminal), while when the FPGA is configured to PCIe x1 it is not detected on each power cycle - the detection seems to be random.

  1. Is there a way to announce to the Jetson how may lanes the provided PCIe endpoint is to be expected, is a HW configuration (i.e. setting the non-utilized lanes to pull up)?
  2. Table 16 in NVIDIA Jetson TX2/TX2i OEM Product Design Guide details up to 6 different configurations. How actually a configuration is selected, is there a HW/SW settings which enables us to select it?

Regards, Igal.


Is PCIe x1 never being detected or sometimes? Please refer to TX2 adaptation guide to see the sw settings. Though I think the default setting is correct.

It is sometimes being detected. Moreover the documents states that the PCIe connector is only supports the x4. Did I get it right?

The dev carrier is x4 (I’ve used x1 on it). It would depend on which carrier, but I don’t think any carrier works beyond x4. An x8 physical slot might exist, but would likely be at max x4 electrically.


I am not interested in x8, I need that a x1 PCIe board will work on the Jetson TX2 evaluation board.
Does the Jetson TX2 evaluation board supports x1 by default or not? if not, what should I do to make it support the x1 PCIe?

Yes, an x1 board will work on the development carrier board. It is rated up to revision 2 of the PCIe spec (PCIe v2 or PCIe rev.2).

Shorter boards with fewer data lanes will all work in longer physical slots. The detection of number of lanes is automated and longer slots with more lanes simply ignore lanes not connected and use what is available. My ethernet card is x1 and works on this x4 slot.

Perhaps the biggest challenge is that with no chassis it is hard to keep the board mounted exactly as is needed if there is any external part touching the card. In my case it is an ethernet card, so it is “a bad thing” if anything bumps the ethernet cable or if for any reason any torque is applied to the slot. It might help to know it is a mini-ITX form factor.