2023-10-21 (Sa) DTMF_Decoder Test circuit

I wanted to show off the Phlute. Most people can recognize when two tones are in the range of phone touchpads, but I wanted to show they were accurate; otherwise it was just pretending to be a red box. I had a few DTMF decoders and some microphone modules in my stock. I had no idea if the amplifier would overpower the decoder or if I would need to attenuate the signal. It was also necessary that the circuit had no programmable hardware to show my Phlute did not require software to assist inexpensive decoders.

I had never used the decoders, so I knew little about their outputs. I connected a 3mm LED to each output and grounded them. The microphone module had an analog output, which I connected to the decoder board's input. I powered everything with a USB power supply.
Using phone to test circuit

The electronics powered up safely, and I tried to trigger it with Phlute, but it was late, and I did not want to disturb anyone. I used a DTMF generator app and confirmed that the decoder could "hear" the tones. The LEDs followed a binary pattern for all the buttons except D. The onboard LEDs flickered, but the outputs remained lit.
Testing Phlute

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