HPE FlexibleLOM to PCIe adapter

This PCB is an adapter that allows using HPE FlexibleLOM cards in normal PCIe x8 slots.

Ordering

Make sure to order this PCB with ENIG finish and beveled edges. Else contact might be poor or your PCIe slots could be damaged.
When ordering through JLC I'd recommend enabling the "Impedance" option and sticking to the default JLC7628 stackup during ordering.

Assembly

The board requires just a stradle mount PCIe x8 connector to be fitted. You can get it at LCSC: C404097

Mechanical mounting

This board has been designed to bring the front FlexibleLOM mounting hole as close as possible to the PCIe bracket retention screw on a full size PCIe slot. You can use a small angled metal piece or a even a 3d printed one to mount the card into place.

Jumpers

This adapter cards has several jumpers. You should not need to touch them, however the following sections will explain their purpose.

PERST

This jumper selects where the PCIe reset signal is routed. By default it is routed to A1 on the FlexibleLOM slot. I believe this to be the PCIe reset signal. However, there is also another pin on the connector, A14 which behaves similarly to A1.
Testing has shown that the cards does not always enumerate properly when using A14 as PCIe reset.
The two resistor footprints next to this jumper can be populated in case you are having issues with floating resets on the cards resulting in spurious resets. I have not encountered any such issues.

Vdet

The Vdet jumper bridges +12V to pin B1 on the FlexibleLOM slot. I assume B1 to be some sort of voltage detection pin since it is routed very differently from all other +12V power signals on the card.

3v3 aux

The 3v3 aux jumper connects what I think is the auxiliary 3v3 volt voltage supply on the FlexibleLOM slot to the auxiliary 3v3 supply of the PCIe connector. Most cards I've seen do not use this voltage rail. However I assume there might be some that utilize it for WOL capability.

lanes

This jumper controls which PRSNT2 pin is bridged to PRSNT1. It defaults to PRSNT2 for 8x cards since that is the maximum number of lanes on a FlexibleLOM slot. You can try setting this jumper to 4x if you are having issues with card detection.
However, a lot of modern devices tend to ignore the PRSNT2 line and rely solely on detecting the lane transmitters/receivers. Thus this setting will be irrelevant for most devices.