Train travel from Barcelona or Madrid to Porto

You would think it would be easy, but public transport travel between Spain and Portugal is not always straightforward.
I don't see any results on the Renfe website, not sure what is up with that. Google results show bus options. Please add the date so those who know more than me can advise.
Have you been to Madrid or Barcelona, or anywhere in Spain or Portugal before? That will help with suggestions.

One option you could consider is Madrid, train to Salamanca, then bus to Porto--but that is a 5+ hour bus, not ideal!

The only train reaching Porto from Spain is a train from Vigo. Vigo is not very interesting, but it is fairly close to Santiago.
You could realistically do Madrid (3-4 days) -> Santiago (2-3 days) -> Porto all by train.
But only worth it if you really want to travel by train; Santiago to Porto is faster by bus, and as you can see on the map, the whole route is far from direct.

It would probably be more efficient to stick with Barcelona & vicinity OR Madrid & vicinity for the whole 6 days, then fly to Porto.

@valadelphia
Dates are July 22-28. Never been to Spain. Have been to Lisbon, Cintra and surrounding areas.
Open to any and all ideas. Thanks!

Thanks for adding that--see Balso's comment above, I was worried I could be missing something with the train schedule, but I was not. They make the best suggestion if Barcelona or Madrid is a must for you, but really anything is on the table.
Northern Spain would be quite appealing to me in late July!
Be sure to read the post about drought issues in Barcelona.

Madrid can be quite hot in mid-summer. Barcelona will likely have lower temperatures, but there's a risk of humidity there. Plus the area around Barcelona has a severe drought now that doesn't seem too likely to clear up before your trip.

In your shoes, I'd consider the Basque Country, Galicia (around Santiago de Compostela) or the coastal area between those two regions. That part of Spain tends to be cooler, overcast and sometimes rainy even in the middle of the summer. Rail links from Madrid to those regions historically haven't been super fast, but recently a new high-speed line was opened that will get you from Madrid to Santiago de Compostela in less than 4 hours. You can easily enjoy 5 or 6 days in Galicia, visiting small cities like Pontevedra, A Coruna and Betanzos and little towns on the west coast like Cambados and Combarra. Galicia is a pretty area, and there's good transportation within that region by train and bus. It's relatively easy to travel from that part of Spain down to Porto.

If you'd prefer the Basque Country, you could take a train to San Sebastian (more options and faster than going to Bilbao) and spend your time there. There are buses from San Sebastian to Bilbao and interesting side trips from both those cities. When you're ready to move on to Porto, you'd be able to fly non-stop--but check skyscanner.com carefully to see whether there's a flight every day. There was one at 7 PM on the random summer day I checked.

@acraven This is very helpful! Thank you!

Faster and cheaper to fly from Barcelona or Madrid to Porto.

I didn't make it clear in my earlier post that the flight I was alluding to is from Bilbao. That's a busier airport than San Sebastian's.