The 26-year-old, released by Oxford at the end of last season, impressed manager Gary Johnson in the 5-3 friendly win over Forest Green Rovers.
Davis, who began his career at Fulham, joined Coventry in 2005 where he made 11 appearances and moved on to Northampton, where he played under Johnson, in 2008.
He switched to Oxford in another free transfer in 2011 and made over 50 appearances for the U's over two seasons.
- Sports & Recreation
- Forest Green Rovers