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FONA 3G and Feather stuffed into Trimline rotary phone
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FONA 3G and Feather stuffed into Trimline rotary phone

by rskup on Sun Oct 25, 2020 6:28 pm

Just wanted to post a brief summary of my Trimline Rotary Cell Phone build and thank Adafruit!

After seeing Justine Haupt's unique rotary cell phone (https://www.wired.com/story/justine-haupt-rotary-phone/), I decided I needed a rotary cell phone. However, since I don't have a 3D printer to make a custom case, I opted to try to modify an old Trimline rotary phone.

I began the project using a FONA 3G and an Uno, following Adafruit's detailed tutorial to learn about the FONA 3G. Then replaced the Uno with a Feather (#2771) for its smaller size and the ability to power both the FONA 3G and Feather with just one LiPo battery.

Adafruits small JST connector switch (#1863) is hidden behind the removable Trimline logo to power the Feather.

As far as how the phone operates, pressing the "hook" button just below the dial gives you a dial tone (just like the "old days") for dialing, or allows you to answer the phone when ringing.

I also coded several "special" two-digit numbers. For example, dialing 92 sends the "AT+CREG?" query to the FONA. If "0,1" or "0,5" is the reply, the "service acquired" tone is played (AT+CPTONEEXT=62). Dialing 90 sends the “low/high” signal to the FONA's Key pin to turn the FONA off.

The pic in the middle shows where I mounted the parts inside the phone (note the battery has been draped over the side so that the Feather is visible). I did end up downsizing to a 500mAh battery to make it easier to fit everything inside the phone. The speaker is under the FONA and the microphone is under the Feather.

Big thanks to all the folks at Adafruit for making these cool boards and having such helpful demos and tutorials on their products, I never could have done this otherwise! It's been a great learning experience to essentially build my own working cell phone.
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rskup
 
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Please be positive and constructive with your questions and comments.