Show HN: Rotary Phone Dial Linux Kernel Driver

Back in the late 70's, I made a rotary phone dialer for my HP41C calculator. I connected a NC reed relay to the piezoelectric beeper and put the NC contacts in-line with my telephone line. I used "synthetic programming" (undocumented opcodes) to get the short duration beeps needed for the dialing pulses. I could enter a name (alphanumeric!) and it would look up and dial the phone number.

About 10 years ago, I met a guy named Keith Jarret at my company. As I was about to ask him if he was the Keith Jarrett who wrote a HP-41C Synthetic Programming Manual, he interrupted me and said, "No, I'm not the musician. Everybody asks me that." So I finished my question and he was very happy and surprised, because he was the author of the book I had read 35 years prior.

https://picclick.com/HP-41-Synthetic-Programming-Made-Easy-b...

https://www.hpmuseum.org/prog/synth41.htm

When the iPhone was just a rumor, I suggested that making it with a touch wheel like the iPods of the time would be a great opportunity to bring back rotary dialing. This was soundly rejected by all present.

Thanks to this, all I need to do is set up a Linux box so I can have that classic rotary vibe!

About time somebody put that rotary phone to good use and beat Dark Souls with it.

This article pops up as I have a rotary phone disassembled right on my desk (rewinding the clock spring). Neat coincidence!

Very nice! I love these minimal driver implementations. It shows off how little actual code you need for a driver (but also how many flags and kernel methods you need to know exist to make a basic driver work).

>Initially, I intended to reimplement the driver in Rust to explore the state of the Rust for Linux project. Unfortunately, I soon realized that the necessary bindings simply are not available yet, so that part will have to wait.

That's interesting (and quite disappointing, though hardly unexpected). I think documenting your approach and the setbacks you've encountered could make for an interesting blog post, if you care about writing such things.

Need a DTMF version.

There's a guy in Australia who makes tiny line-powered boxes that translate rotary pulses into Touch Tones.

They let me keep using my rotary phones until a few years ago when I moved into a building that had no POTS wiring. Sad.