Two ways by which audio files can be played using Arduino.<\/p>\n
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- PWM (Pulse width modulation) – Arduino does not have a DAC. PWM signal is used as a substitute for DAC by accepting some degradation in performance.<\/li>\n
- External DAC \u2013 An external DAC interfaced with Arduino for proper audio signal conversion.<\/li>\n<\/ol>\n
PWM audio signal <\/strong><\/p>\n
Arduino has PWM gpio\u2019s. We can easily output an audio signal data stream as a PWM signal. The idea is to output the audio as PWM, which is then fed to a transistor. Transistor, after some gain, inputs the signal to the speaker, and finally, we can hear the audio.<\/p>\n
Can we play all the audio files (mp3, wav, mp4, wma, etc.) using Arduino?<\/p>\n
The answer is no. We can only play files whose contents are aligned as linear binary data. Arduino can read files. It can\u2019t decode files. So, if the file content is encoded, it can\u2019t be read by Arduino. Also, Arduino is an 8-bit microcontroller. It can read data which is 8-bit wide. By analyzing the above constraints, only wav audio files are found to be suitable for Arduino.<\/p>\n
Wav audio files can be sampled between 8KHz to 44.1KHz. Sampling means that particular audio is recorded at this rate. Bit per sample is another characteristic for wave file is 8 and 16. The number of channels is mono (1) or stereo (2). \u00a0For other parameters, you can see the file format stack. The above three are of our concern.<\/p>\n
Arduino Uno’s max clock frequency is 16MHz. To play the .wav file, we must decrease the .wav file sampling rate to 25KHz or lower (considering the Arduino machine cycle is 1). This is to avoid hearing something out of order. We can play the wav file, which is sampled at 44.1KHz, but the Arduino machine cycle is increased in our case. We are fetching data from an SD card. Then the timer is converting the data in PWM form, and at the end, we are outputting it on the PWM pin. This whole process increases the time, and we may not play 44.1KHz sampled audio, especially if the frequencies are higher in audio.<\/p>\n
Bit per sample must be 8, and lastly, only mono channel guarantees linear bitstream. Many online tools are available through which you can transform wav file according to the above parameters. After transforming the copy, the transformed the wav file in SD card.<\/p>\n
A circuit diagram of the project is given below.<\/p>\n
![\"\"](\"https:\/\/www.engineersgarage.com\/wp-content\/uploads\/2021\/03\/Arduino-audio-player-figure-1.jpg\")
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