tapeDuino: breadboard purgatory!

Then… Out comes the breadboard. And, whoa! It’s in a state of disarray. For a while, one of the first things I bumped into was the op amp circuitry in the IC. It took quite a bit of turning, throwing in and tearing out pots, tuning them, trying again, and again and again. My suggestion is to test DTMF output from a variety of devices into the 8870 (the DTMF decoding chip). You’ll find a sweet spot that will work for all of the devices. Too much gain, and you’ll get nothing. Too little gain, and you’ll miss digits. In this process, I was constantly changing up the breadboard, hence the ton of test leads.

In that video you’ll see that what I’m decoding is output in binary on 4 LEDs. You’ll see the pattern cycling through counting from 0 to 15. (Or if you need a refresher on counting in binary, wikipedia can help)

The DTMF output example sketch from the Tone Library is nice, doubly so in that it outpulses 867-5309, Jenny (factoid: Most people think the 555 fictional exchange came about because of that song, but, it only caused a gain in demand for fictional numbers due to it). Is there any other number you should first decode? Historians have unilaterally decided: No.

I’ve got some demo code from when I was first decoding from the 8870, if it comes in handy.