There are plenty of micros on DigiKey with USB that don't show up when I just search for USB because they have other connectivity options, e.g. the PIC16F1454 doesn't show up because it has I²C, LIN, SPI, UART/USART as well as USB. If I were to search for every connectivity combination that includes USB I would be there for hours though, as there seems to be over 350 combinations that include USB. Is there a better way?
No, you can do it, I frequently do that same search "USB" on Digi-Key, as I want to see what ones are available, but insist on USB.
I think you selected the "USB" option in the parametric search. Unfortunately, that does NOT work out too well. As I think you just found out.
The way to do it on the Digi-Key web site, seems to be, that you choose the basic MCU you want. I.e. you may have hundreds or thousands, showing up in the search results. Then within the "Search Within Results" box, towards the top. Put in "USB". It should now say (after clicking), "Search Entry: usb [x ] ", and restrict itself to ALL Mcus, with USB capability.
Here is one I did for you, as an example:
http://www.digikey.co.uk/product-search/en/integrated-circuits-ics/embedded-microcontrollers/2556109?k=usb&pkeyword=&FV=fff40027%2Cfff800cd&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25You can add multiple search parameters that way. E.g. If you must have at least one SPI port, you can add that in the same way. You can have as many terms as you like, as far as I can tell.
The parameter search DOES work, but you have to click/highlight EVERY USB entry and there might be fifty or hundreds, so that is NOT a good way of doing it. I think you ONLY clicked on one of the parameter USB lines, all 50..100++, would have been needed. Hence why the refine search method is easier/best, apparently.