I am attempting to build an audio recorder with what supplies I have on hand. I intend to use the max4466 as the input and one of several microcontroller boards in the process. I have at my disposal an Elegoo Uno R3, Arduino Nano 33 BLE, Arduino Nano CH340, and an ESP-32S board. I would like to use one of the Nano boards. I would also like to use a pushbutton (I have one) to begin and end the recording.
I've successfully run this project from Adafruit website to measure input but am having difficulty a) recording longer and b) converting to audio file such as .wav or .mp3. I am running macOS big sur and have had no issues with Arduino IDE or board connection.
My skill level is approx 4/10.
Any tips? Thanks a ton!
Theoretically it's pretty simple to record & play a WAV file. MP3 is more complex. LAME is an open source MP3 encoder (and decoder) project but you'd have to "port" it to the Arduino and that's a BIG programming project.
The Uno & Nano don't have a DAC (no true analog output for playback). I don't know much about the ESP32 board. The Uno & Nano are also a bit "slow" and certainly not powerful enough to encode/decode MP3 in real-time.
You'll need additional storage (an SC card, etc.). You may not need CD quality audio, but CD audio is 44,100 samples per second so at 16-bits you need more than 5MB for one minute (double that for stereo). Of course, MP3s can be 1/5th to 1/10th that size.
The Audacity website has an easy introduction to digital audio and here is the WAV file format.
What audio quality are you wanting? That will determine the sample rate and bit depth, which will be important in choosing a microcontroller.
Good enough quality for intelligible speech
8 bit 8kSPS is enough for that. You do need a suitable anti-alias filter when sampling at a low rate like 8kSPS though.
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