I ran into this a few years ago with a cots GNSS product. Their datasheet said it supported 232, 422, maybe 485. But they didn't say how to select any of them a

I ran into this a few years ago with a cots GNSS product. Their datasheet said it supported 232, 422, maybe 485. But they didn't say how to select any of them and when I probed, it was I think 422. It was certainly 0-3v. Not wanting to send -15V to a standard digital logic chip, I contacted the manufacturer. Weeks of going back and forth with their sales team on the phone and email. They insisted that was 232 because the 3v is within some range. Eventually they let me talk to an engineer who within seconds said "it'll auto detect from the negative voltage." It did and we closed off that task. Easily the most frustrating manufacturer interaction I've ever had. They could've just put that in the datasheet.