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Sending Messages through the Pony Express

Updated: Sep 27, 2022

Have you ever wanted to send a discreet message to someone on the subway, elevator, or other crowded public space?

Back in the olden times, one of the fastest ways to get a message across was via horseback! The Pony Express operated from 1860-1960 between St. Joseph, Missouri, and Sacramento, California.

Shirley and I came up with the idea to create a discrete local messaging system, kinda like passing notes in class or whispering something to your dinner partner. We present to you... the e-ink Pony Express!

The e-ink Pony Express delivers a message from your phone... to the back of your phone! No need to show someone a message on your screen while fearing that an embarrassing notification or pop up will show up.

This device attaches to the back of your phone and can read any message you send it!


How we made it

The device is an e-ink screen connected to an Arduino powered by a battery, that is also connected to an DTMF encoder that accepts dial tones straight from your phone.

Shirley made a website with a text box that translates any ANSI character to a 3-digit value that is output as dial tones corresponding to this dial tone frequency chart

We struggled a bit to figure out how to use the iPhone/Android plug to send power AND data. I'm still not sure if it's possible, but we ended up powering the Arduino with an external battery that Shirley made in her homemade hardware class.

I then assembled the enclosure to the exact size of an iPhone Mini, which is the smallest iPhone, and would therefore be an adequate size for any iPhone model.

I modeled the enclosure in Rhino and milled the front and back faces in white acrylic that was left over from the summer (woo!). The surround was 3D printed, first in two halves, then as a whole piece.

This was a fun project! We learned a lot and were able to flex our strengths.

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