He also scored eight goals in a previous loan spell.
Tykes boss Andy Ritchie said: "It's good news. The chairman had another good meeting with Danny's agent yesterday and he is expected to sign today.
"I'm very pleased. We know he's a good goalscorer; we need a potent strikeforce and we think we'll have that."
He joins ex-Scunthorpe duo Paul Hayes and Richard Kell, and former Swindon winger Brian Howard, in signing up at Oakwell this summer.