WiFi details via NFC

This seems a no brainer - an NFC tag that provides WiFi details. Perfect for people to get WiFi details when physically present, e.g. in bar/restaurant and so on. NTAGs are available as stickers even, great to stick to a menu, etc.

So I coded it, using a PN532, and making a client (card/tag) work.

This was not simple!

• Some aspects of the NFC / NTAG / NDEF are in specifications you have to buy.
• It is layers on layers on layers, so a nightmare to work out - many hidden in the PN532 itself.
• It is different choices for layers - it seems the host and card can work in a variety of ways, including DEP, PICC, and a raw tag format. The cards/tags and phones seem to handle various ways of doing it. I really struggled with some of them - the PN532 claiming not in the right mode or that I have a wrong header of some sort. Drove me round the bend. Finally managed a sort of raw tag initiator/response message thing that worked.
• NTAG and NDEF coding is fun, LOL, well more layers.

The first step was a simple NDEF URL, which is not hard. It has a type (U) and a byte for well known prefixes (like https://www.) and the rest of the URL, all wrapped up in a message format in another message format logically in memory on the card. That works.

The next step was WiFi, and this is a pain in the arse. Again, layers of stuff, but this time the type is a MIME type tag application/vnd.wfa.wsc and it has an ID (0). Then the content is a list of tag/values, but not a simple one (i.e. some implicit lengths). However, I was able to make it all, based in part on an actual NTAG card programmed with WiFI using an app. I was able to read using the NTAG app.

But I missed a step - I did not try the real tag on my iPhone. If I had, I would have realised that it does not work on an iPhone!

I have found issues listed on the internet where people have been hoping iPhone will handle this for years. Some suggested it is a security issue? But I cannot see how it worse than a QR code with WiFi, and that works. So weird.

So please, Apple, support NFC WiFI details!