Peaceable Projects Inc. is a U.S.-based non-profit group that brings the vast resources of the wide world together with the ongoing needs of the people who live, work, and travel on the Camino de Santiago pilgrim trail network in Spain.
My bet is that you will have to change in Braga. If you go to the Rede Nacional de Expressos website, http://www.rede-expressos.pt/, and click on "horarios", you'll see you can go Barcelos to Braga on one of four buses, 6:30, 8:30, 13:30, and 18:30. It's about a half hour ride. Only the later two buses are daily, the first on is only M-F and the second one doesn't go on Sunday.
Then, once in Braga, it's another half hour to Ponte de Lima. It looks like (though I find this surprising) there is only one bus a day from Braga to Ponte de Lima, leaving at 6:30 pm daily, which is the same time that the latest bus arrives from Barcelos. So the latest you can leave Barcelos is on the 13:30 bus, which means you will have a layover of at least 5 hours.
BTW, I think you will easily find ways to entertain yourself in Braga for a day. It's a lively provincial city with a nice old core, some very nice cafes, plazas, fountains, etc, along with its very old cathedral.