How to use nRF52 series to play mp3 audio file

RE: How to use nRF52 series to play mp3 audio file

NewtoM — Tue, 09 Nov 2021 21:13:42 GMT

Hi Thomas, this is possible. For simple (voice quality) tasks, you can use PWM output (have a look a this thread: https://devzone.nordicsemi.com/f/nordic-q-a/52878/pwm-audio-driver), for high-quality output use e.g. the MAX98357A I2S amplifier. I managed to combine both with a minimalistic mp3 decoder implementation (https://github.com/lieff/minimp3) and they work great. Unfortunately I am not allowed to show full source code, though.

RE: How to use nRF52 series to play mp3 audio file

Einar Thorsrud — Thu, 27 Aug 2020 13:29:47 GMT

Hi Thomas,

[quote user="arctommy20"]Case1(simple audio). nRF52 (store opus audio format on external flash) > use PWM to output simple audio > to audio amplifier to drive speaker[/quote]

We only have examples using Opus for input from a PDM microphone (in the smart remote 3 reference design), but that is a possibility. Note that after decoding you would have to convert to a PWM signal. There are no official examples of that, but it should be possible.

[quote user="arctommy20"]For case 2, we use PWM or other I/P to output to external DAC? Please advise. Thanks[/quote]

No, you would not use PWM to the DAC. Most likely you would use I2S if you are on the nRF52840. Essentially you need to use an interface that is compatible with both the nRF device you use and the DAC, so you must select an appropriate DAC.

RE: How to use nRF52 series to play mp3 audio file

arctommy20 — Thu, 27 Aug 2020 02:59:04 GMT

Hi Einar,

Thanks for your information.

I want to verify the below flows of playing Opus audio format on nRF 52 series as below:

Case1(simple audio). nRF52 (store opus audio format on external flash) > use PWM to output simple audio > to audio amplifier to drive speaker

Case2(good quality audio). nRF52 (store opus audio format on external flash)> use( PWM or other I/O port) to output to external DAC > to audio amplifier to drive speaker

My flows are corrected or not? Please advise

For case 2, we use PWM or other I/P to output to external DAC? Please advise. Thanks

Best Regards,

Thomas

RE: How to use nRF52 series to play mp3 audio file

Einar Thorsrud — Wed, 26 Aug 2020 12:23:18 GMT

Hi,

I am not aware of any implementations of an MP3 decoder on an nRF52 device, but it may be possible depending on the complexity. There may be other more suitable codecs (such as Opus or similar) if you do not require MP3 specifically. You could use the PWM peripheral to output simple audio, but you may find that an external DAC is needed for good quality audio.

Perhaps someone from the community has experience with this and want to comment?