The WISP5 is an open source project!
You can find our firmware repository for the WISP5 at github.com/wisp/wisp5. Keep in mind that there are sometimes multiple branches which support different protocol details.
There is now a version of the WISP5 firmware, not officially supported by the WISP team, which works with the Chinese version of Impinj Speedway R1000 readers:
If you're not familiar with Github or the Git version control system, there are a lot of good resources online about how to get started.
Please submit your bug reports as Github “issues” and feel free to submit pull requests as you find solutions to bugs, make changes, or add features to the WISP5 firmware. The firmware is an evolving and open collaborative project in which you can play a part!