How is the precomputed table for 25519 Elliptic curve generated?
CodesInChaos created an exact gist in C# for this:
https://gist.github.com/CodesInChaos/ef914909941ce7caf514

It worked for me, took around 8 seconds on a 48MHz 32bit device, but either way, works.
My C port can be found here
https://gist.github.com/irfansehic/9c0b204845370f372bdfccfb66ec5942