The Arsenal midfielder has joined the Championship club for an undisclosed fee after injuries disrupted his chances of regular first-team football at the Emirates Stadium.
Frimpong endured an injury-hit career with the Gunners where, after emerging from the club's academy as a promising young midfielder, knee trouble that required surgery on three separate occasions hampered his progress.
"AFC thank you for the memories thanks for the support thanks for the Love," Frimpong wrote on his Twitter account. "I wish the team wins the league this year.Forever will be in my ❤️”
The Ghana international has previously been out on loan with the likes of Wolves, Charlton and Fulham but has decided to leave Arsene Wenger's side on a permanent basis having spent 13 years with the Premier League club and made 16 senior appearances.