Modding a Touch-Tone Phone to Play .wav Files

Happy 20th anniversary of ilovebees! I was thinking about this the other day and as my mind wandered, I thought, “Wouldn’t it be cool if you could have a touch tone phone, and if you dialled a number, it would play one of the audio clips from the ARG?” And then I searched for it, and found this link:

https://www.digikey.com/en/maker/projects/touch-tone-phone-dial-a-song/ae4fd7386c844a14a23d246330bca340

Later I found a better link. The one above has broken links to the software needed, but this one works better:

https://learn.adafruit.com/touch-tone-phone-dial-a-song/overview

And after a month on and off (mostly off) I have a working phone. Check my instagram for a video of the working circuit/program.

I’m going to get more detailed about what I did, what worked, what didn’t, what had to change, etc. so if you’re interested in doing this yourself, you’ll avoid the problems I ran into. Probably the big one for me is that I had no experience soldering electronics. It is not easy. It is absolutely necessary. But it is nowhere near as necessary as I made it. I ruined a couple of electronics components because I tried to pack too much into a small space.

Let’s talk about the bits and bobs you’ll need to make this. Refer to the website above.

1. Adafruit Feather RP2040. Absolutely necessary. Comes with a set of posts that you’ll need to solder to the board. This is necessary, but if you’re careful, not terribly difficult. (<$20)
2. Featherwind Doubler. Not necessary. It comes with some items that can make your life easier. Instead of the posts that come with the Feather, it has headers. Basically posts that have openings on the other end that other posts (or jumper wires) can be put into.
3. Audio Amplifier. Necessary. Also comes with posts. And a connector for the phone receiver. (<$10)
4. Battery. Not necessary. I got it, plugged it into the board far too early, and burned out the board. You need to be done before you plug the battery in. It may be obvious to you, but it wasn’t to me.
5. Terminal Blocks and Wire ferrules. Both unnecessary.
6. USB Adapter. Necessary. This is nice because the wires have connectors like the headers. (<$20)
7. Jumper Wires. Necessary if you want to minimize soldering. (<$10 for over 100 jumpers)
8. Resistors/Capacitors. Necessary. I had these from other kits I’ve gotten over the years. (<$30 for hundreds of resistors and 10 capacitors)
9. Telephone. Obviously. I didn’t get the model they have here. I went with “Home Intuition Classic Corded Phone for Hearing Impaired Telephone for Seniors with Extra Loud Ringer” from Amazon. One nice thing about it is that it’s a newer phone, so a lot of the connectors inside will easily accept jumper wires from item 7 above. (Approx $40)
10. Another thing I recommend getting is several Mini Breadboards. They can take the place of the Doubler in item 2 above. Again, I had several of these from previous kits. They are great because they have an adhesive backing that allows you to easily attach them inside the phone. (<$10 for six)
11. For this project you’re also going to need a “MicroSD SPI or SDIO Card Breakout Board” (Get one that is only 3 Volts, not 5V) and a MicroSD card to hold all of the files. It turns out that the Feather has very limited onboard memory. The project is designed/programmed to play wav files and not mp3s. Even if playing of mp3s was possible, they’re still too large to fit on the Feather. All of the ARG audio files as mp3s are a total of 130 MB, and after converting them to wavs, they’re 819 MB. (<$20 for the board and a 32 GB MicroSD)

Total price is pretty close to $150 (assuming you have solder and a soldering gun, spare USB cables to plug the feather into your computer, a computer, etc)

I’m going to make this guide parallel the source material, with each section making up another page. Next up, the Python and the Program

Phone-Modding Part 2, the Python and the Program