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A modified mid-1980s Panasonic T36 electric typewriter can print incoming SMS messages, including the sender’s name and a timestamp. It does not have cellular messaging built in: an ESP32 and custom electronics translate message data into signals that mimic pressing keys on the typewriter.
What the texting typewriter does
Engineering and robotics teacher Sam Christy adapted a Panasonic T36 to turn received texts into printed copy on a roll of typing paper. A local phone directory on the ESP32 supplies names for sender identification. The result combines a vintage machine’s mechanical printing with a modern message-delivery system.
The project is a one-way SMS printer in the documented version. Christy described adding a keyboard to reply to messages as future work; the available project documentation does not establish that replies were implemented. Christy’s hardware write-up and software write-up describe the build.
How a text reaches the typewriter
- An SMS arrives: A Twilio phone number receives the inbound message and forwards its data through a webhook.
- The local service receives it: The documented setup uses ngrok as a reverse proxy to make a service on the local network reachable from outside. Christy runs ngrok on a Raspberry Pi.
- The ESP32 prepares the print job: The ESP32 application handles the incoming request, extracts message and sender details, and looks up the sender’s name in a local phone directory.
- The interface circuit operates the typewriter: The ESP32 sends commands over I2C to custom electronics, which route signals through the keyboard matrix so the typewriter prints the text, sender identification and timestamp.
Christy’s software account describes the request-handling path; Hackster.io’s technical account also outlines the network and hardware flow. These sources document the project architecture, not current Twilio or ngrok service terms.
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How the electronics simulate typing
An electric typewriter’s keyboard is arranged as a matrix: pressing a key connects particular lines, and the machine scans those connections to determine which character to print. The interface circuit must reproduce the appropriate electrical pattern without relying on a person to press each key.
The documented circuit uses an MCP23017 I2C I/O expander along with 74HC logic, including 74HC151 multiplexers and a 74HC138 demultiplexer. A 74HC4066 analog switch and signal-filtering components are also named in the build. SHIFT and CODE need separate handling, adding complexity beyond simply routing ordinary letter keys.
That keyboard-matrix problem is why this is more than attaching a phone to a printer: the controller has to present the right signals at the right time for the typewriter’s own scanning circuitry. The hardware documentation explains the interface design.
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What is established—and what is not
- Demonstrated: Receiving SMS and printing the message, sender name and timestamp on a paper roll.
- Working example: The Panasonic T36. Christy says the hardware was designed with other electric typewriters in mind, but the cited documentation establishes the T36 as the working machine, not universal compatibility.
- Model-specific adaptation: Other typewriters may use different keyboard matrices or timing, so connecting one would require investigation and potentially custom circuitry.
- Not confirmed: Sending replies from the typewriter. The hardware post describes a reply keyboard as a future addition.
Christy’s hardware post also notes that an earlier version divided tasks between a Raspberry Pi and an Arduino; the later design places message handling and file retrieval on the ESP32, with a separate I2C-controlled circuit routing typewriter signals.
Parts named in the build
The documented system includes an ESP32 development board, an MCP23017 I2C I/O expander, 74HC151 multiplexers, a 74HC138 demultiplexer, a 74HC4066 analog switch, signal-filtering components and an 11-inch-wide roll of typing paper. These are components of a custom project, not a plug-and-play kit; the circuit and typewriter interface require model-specific consideration.
Why the project stands out
The charm is easy to grasp: a message normally read on a screen becomes a physical page produced by a machine from another era. The technical interest lies in the translation beneath that novelty—networked SMS data becomes I2C commands, then carefully routed electrical signals that the typewriter interprets as keystrokes. Hackaday covered the project as a meeting of old machines and modern technology in its December 18, 2024 article.
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