Martin, 27, is 6-foot-5 and finished last season with the Celtics after signing a pair of 10-day contracts in February and March. Before that, he spent 27 games with the Pacers, prior to being waived in January.
He also played 35 games for the Pacers in 2020-21, one year after appearing in 31 games with the Timberwolves as a rookie.
Meanwhile, second-round pick E.J. Liddell, who suffered a torn ACL in summer play, remains unsigned.
Martin went undrafted out of Butler in 2019.