A Linux kernel driver that turns a rotary phone dial into an evdev input device. You might be interested in this driver if you
- prefer the slow pace of dialing over typing numbers with your numpad,
- want to bring your old rotary phone into the digital era,
- are an educator looking for a simple example driver with a VM-based end-to-end development & test environment (no real hardware needed)
- have another creative use case in mind!
This driver was my introduction to embedded Linux years ago—and ultimately led to my career. However, it remained unfinished and unpublished until now. 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.
About 10 years ago, I met a guy named Keith Jarrett 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
We used it as a speed dialer that worked on any phone.
I still have the hard copy of the synthetic programming guide!
Even outside of that technique, the calculator was a very powerful programmable tool for the early 1980s.
The same friend and I also wrote a program for performing all of the calculations for a grad class in S-parameter modeling of RF transmission. We were so proud, we showed off the program to our professor. Our "reward" was having calculator "programs" banned during all tests 8-/
We didn't realize until later, that there was a "turf war" going on between the RF section of our EE department, and the digital electronic section.
This is how the HP-41CX calculator helped me learn one of the most significant lessons of my EE degree: when it comes to human decision making, the tech is often far from the top priority.
The dialer was one of only two mods that I had made to my 41. I brought out the piezoelectric wires via a two-pin female .1" "berg" connector that I had added to the lower right side of the case. (I wish I had a photo.) The other mod used similar hardware; I put a magnetic reed switch inside, which changed a capacitor value for the system clock when a small magnet was attached (via Velcro) to the side of the calculator. The result was that my 41 would run its programs twice as fast. I had to remove the magnet to use my auto-dialer, because otherwise the timing was wrong. In my area, GTE didn't switch to ESS for another 10 years. Oh the fun!
I may still have a spiral notebook, in which I did all of the code development. It would be a hard-copy of all the code I wrote. If I do still have it, I have no idea where it is. It sort of reminds me of the end of Citizen Kane.
Later on, I also got rid of my Synertek SYM-1 and all my CP/M platforms, except for one IMSAI 8080 S-100 box, which I eventually gave away to someone else. I didn't realize at the time (nearly 30 years ago) that the IMSAI 8080 was quite collectable, and was going for about $800 on eBay. Still, I didn't regret it much.
The old systems evoke a sympathetic nostalgia, but actually using them is an exercise in patience, and eventually evokes a desire for more modern systems.
I've still got some emulated retro hardware and some old software emulators, but I don't really use them much.
https://hackaday.com/2024/10/31/bakelite-to-the-future-a-195...
https://blog.waleson.com/2024/10/bakelite-to-future-1950s-ro...
Creating an alt mode for a bluetooth rotary numpad shouldn't be difficult ;) Now if I could only find some time.
Would be interested to see a bit of your hardware setup!
Thanks to this, all I need to do is set up a Linux box so I can have that classic rotary vibe!
Steve Jobs was one of the inventors listed on this patent. As it happens, I and another Apple colleague filed an almost identical patent at around the same time. So, for a while, Apple owned two patents for simulating a rotary dial on a touch wheel. (My patent was eventually allowed to lapse. Steve's has been renewed).
I have to say that I had had a bit too much to drink at a dinner in SF when I suggested this idea to my colleague. I was thinking of the old pinball game that had really good physics making it feel amazingly real. I thought that the crucial part was doing the dialing physics in such a way that users could quickly dial any digit with the right gesture.
I was not disclosed on the iPhone when I came up with this idea, but my colleague sent the idea off to the patent committee and they agreed to it! They must have laughed when they saw the similarities to Steve's patent (which was still in progress too). We did have some big differences with Steve's, so it wasn't a duplicate. That being said, I think they wanted to boost the number of patents related to the iPhone as part of the initial marketing. (Steve said that there were already "over 200 patents" for it when he introduced it.)
Then you can use this for typing: https://www.youtube.com/watch?v=9BnLbv6QYcA
It almost feels _impressive_ how hard macOS still is to integrate into an enterprise setting, and maybe they're okay with it just being a running joke for the past two decades that their computers don't do as well in a business context...
https://m.youtube.com/watch?v=BGGOn-H7s3Q
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.
I thought about it, but couldn't find a VOIP service that was the right combination of ease/cost/good hardware.
>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.
It didn't involve a rotary phone directly, but a telephone network that was still compatible with them.
Rather than repeat the story, I'll link to it here:
https://news.ycombinator.com/item?id=40391220
If anyone needs their curiosity piqued, it involved a loud knock on the door and...
"San Jose Police! Open up!
https://www.youtube.com/watch?v=35N5vKKGDy8