Sam Christy is an uncommon particular person. On the one hand, he’s a really technically-savvy person who teaches robotics and engineering at a technical highschool. Alternatively, he doesn’t personal a cellular phone. That is fairly a putting juxtaposition, on condition that we’re gone the purpose the place somebody with out a cellular phone could possibly be seen as something aside from a Luddite.
After all there are various causes one would possibly wish to keep away from cell telephones, regardless of the conveniences they provide. Avoiding calls in the course of the night time, or over the weekend, from an employer that has by no means heard of work-life stability, for instance, could possibly be purpose. However think about not even with the ability to obtain a textual content message these days. There should be some center floor for those who wish to keep related whereas nonetheless with the ability to unplug every now and then.
The keyboard is simulated through an exterior circuit (📷: Sam Christy)
For Christy, the compromise concerned constructing a really distinctive gadget — a typewriter that may obtain texts. Whereas this gadget can obtain SMS messages, it may well hardly be anticipated to sit down on one’s nightstand, or be carried in all places in a single’s pocket. It could appear to satisfy the standards for connectivity with out fixed availability. Furthermore, it gave this engineer an incredible excuse to dive into some cool classic {hardware} and combine some fashionable know-how into it.
The Texting Typewriter is constructed round a mid-Eighties Panasonic T36 electrical typewriter that varieties out acquired SMS messages on paper. It does this by first leveraging Twilio, a cloud-based service that gives the typewriter with a digital telephone quantity to obtain messages. When a message is distributed to this quantity, Twilio makes use of webhooks to ahead the message to an exterior URL related to the typewriter. The externally accessible URL is created utilizing a service known as ngrok, which acts as a reverse proxy to securely join Twilio to a neighborhood ESP32 microcontroller that controls the typewriter. The ngrok service runs on a Raspberry Pi on the native community.
The ESP32 acts because the central controller, working an asynchronous net server that processes incoming HTTP GET requests containing the SMS message knowledge. When a message arrives, the ESP32 extracts the sender’s telephone quantity and the message content material. It then checks the quantity in opposition to a neighborhood telephone listing saved on the ESP32 utilizing LittleFS, a light-weight file system, to match the quantity to a reputation.
As soon as the message and sender particulars are prepared, the ESP32 sends instructions to a customized circuit through an I2C interface. This circuit manages the typewriter’s keyboard matrix by routing indicators between its rows and columns. The circuit makes use of multiplexers and demultiplexers to pick and transmit indicators akin to the keys that have to be “pressed” to sort the message. Particular keys, corresponding to SHIFT or CODE, are activated individually utilizing a quad bilateral change.
Lastly, the typewriter prints the SMS message, together with the sender’s title and a timestamp, onto an “infinite” roll of paper. Not a foul approach to keep related with out being too related, huh? And maybe extra importantly, constructing a Texting Typewriter can be a good way to study extra about know-how, each new and previous.
