Opal Kelly XEM6010-LX150 not available

[jbqubit]

The current digital-servo design relies on the Opal Kelly XEM6010-LX150 FPGA daughter card which is now marked "end of life" due to its dependency on the Xilinx/AMD Spartan series which is out of production. As of 12/2021 Opal Kelly had a small inventory which is now exhausted. I've created this Issue to document this state of affairs. I've also included a synopsis of two email discussions about a path forward. I don't have the bandwidth to support a re-roll of the digital-servo with a modern FPGA but I encourage interested users to pursue this. As ever many thanks to @dleibrandt for making this amazing open source tool!

path 1) As of 1/2024 Opal Kelly was considering making a final batch of XEM6010-LX150. Minimum order quantity is 50 at the cost of $1200/ea. Based on emails of several PIs and technosystem.pl there was insufficient interest to meet this threshold.

path 2) The Opal Kelly XEM-7310 is a potential replacement. However, the way the FPGA pins are wired to the connectors is incompatible with the NIST digital servo daughterboard. You'd also need to modify the design of the daughterboard.