For most people, calculators are cheap and simple devices used for little more than addition and the odd multiplication job. However, when you get into scientific and graphical calculators, the feature sets get a lot more interesting. For example, [Ready? Z80] has this excellent explainer on how HP’s older calculators handle infrared communications.
The video focuses on the HP 27S Scientific Calculator, which [Ready? Z80] found in an op-shop for just $5. Introduced in 1988, the HP-27S had the ability to dump screen data over an infrared link to a thermal printer to produce paper records of mundane high-school calculations or important engineering math. In the video, [Ready? Z80] explains the communication method with the aid of Hewlett-Packard’s own journal publication from October 1987, which lays out of the details of “the REDEYE Protocol.” Edgy stuff. It’s pretty straightforward to understand, with the calculator sending out bursts of data in six to eight pulses at a time, modulated onto a 32.768KHz square wave as is the norm. [Ready? Z80] then goes a step further, whipping up custom hardware to receive the signal and display the resulting data on a serial terminal. This is achieved with a TEC-1G single-board computer, based on the Z80 CPU, because that’s how [Ready? Z80] does things.
We’ve seen other great stuff from this channel before, too. For example, if you’ve ever wanted to multitask on the Z80, it’s entirely possible with the right techniques. Video after the break.
Wow. This is cool. I aged out of having a calculator in the late 70s but have several fond memories incl. HP. This article is in my future.
Remember lusting after an HP 41. My have we come a long ways.
Ugh not another youtube video.
Kinda peeved that my HP 32SII has the same case, with the IR window, but no IR capability.
Doubly peeved on learning they got it for $5.
LOL!
Years ago I worked in a secure faculty. My HP48sx sat on the desk at my side.
One of the security people happened to see it and lost his mind.
Calculators with IR communication aren’t allowed.
So, we took a trip the the head of security. When I saw his 48sx on the desk, I knew it was a nothing burger.
He made a comment like “This thing, communicating with anything? Please be serious…”
And away I went.
It sure would be nice if I could comment here without providing creds EVERY TIME…
If you make a wordpress.com account and login to that, they share cookies or something and it remembers who you are on here
In my experience, the only place where they’re that careful about ALL wireless comm including IR is in a SCIF, but for IR it still seems rather anal since SCIFs most definitely don’t have windows.
HP nerfed the range of the IR communications system to stay within the requirements of a standardized testing body, (College Board or similar) so it really wasn’t a risk for two-way communications, but if I remember correctly the nerfed it on the receiving end, so the calculator could still be used to transmit over a significant distance.
Just today, I had to replace the batteries in my HP 16C for the 3rd time in its (coïncidentally :)) 42-year life span. And this is my daily driver, right… I use it at least every other day.
Manual says that with calculator off, silver oxide batteries will last at least 2 years. :)