STM32 Music Player
Creating an audio player using a STM32 MCU is relatively straight forward, but does include some interesting steps. Audio out could in principle be created using one of the built-in DACs but for better audio quality a proper audio stereo DAC should be used. Fortunately they are readily available and not expensive. Research into audio play on STM32.
Videos
Teaser:
First video in the series:
I2S Audio DAC
To be added
Parsing WAV files
A typical WAV file consist of a header followed by audio data. The header specifies the audio format.
On Wikipedia, the WAV format is described like this:
[Master RIFF chunk] FileTypeBlocID (4 bytes) : Identifier « RIFF » (0x52, 0x49, 0x46, 0x46) FileSize (4 bytes) : Overall file size minus 8 bytes FileFormatID (4 bytes) : Format = « WAVE » (0x57, 0x41, 0x56, 0x45) [Chunk describing the data format] FormatBlocID (4 bytes) : Identifier « fmt␣ » (0x66, 0x6D, 0x74, 0x20) BlocSize (4 bytes) : Chunk size minus 8 bytes, which is 16 bytes here (0x10) AudioFormat (2 bytes) : Audio format (1: PCM integer, 3: IEEE 754 float) NbrChannels (2 bytes) : Number of channels Frequency (4 bytes) : Sample rate (in hertz) BytePerSec (4 bytes) : Number of bytes to read per second (Frequency * BytePerBloc). BytePerBloc (2 bytes) : Number of bytes per block (NbrChannels * BitsPerSample / 8). BitsPerSample (2 bytes) : Number of bits per sample [Chunk containing the sampled data] DataBlocID (4 bytes) : Identifier « data » (0x64, 0x61, 0x74, 0x61) DataSize (4 bytes) : SampledData size SampledData
Looking an example header, it may look like this:
00000000 52 49 46 46 f4 82 5f 03 57 41 56 45 66 6d 74 20 |RIFF.._.WAVEfmt | 00000010 10 00 00 00 01 00 02 00 80 bb 00 00 00 ee 02 00 |................| 00000020 04 00 10 00 4c 49 53 54 c8 00 00 00 49 4e 46 4f |....LIST....INFO| 00000030 49 41 52 54 0d 00 00 00 46 65 6c 69 70 65 20 53 |IART....Felipe S| 00000040 61 72 72 6f 00 00 49 43 52 44 05 00 00 00 32 30 |arro..ICRD....20| 00000050 30 38 00 00 49 47 4e 52 0a 00 00 00 43 6c 61 73 |08..IGNR....Clas| 00000060 73 69 63 61 6c 00 49 4e 41 4d 3d 00 00 00 42 61 |sical.INAM=...Ba| 00000070 63 68 20 2d 20 53 69 6c 6f 74 74 69 20 2d 20 22 |ch - Silotti - "| 00000080 41 69 72 22 20 20 66 72 6f 6d 20 4f 72 63 68 65 |Air" from Orche| 00000090 73 74 72 61 20 53 75 69 74 65 20 4e 6f 2e 20 33 |stra Suite No. 3| 000000a0 2c 20 42 57 56 20 31 30 36 38 00 00 49 50 52 44 |, BWV 1068..IPRD| 000000b0 2a 00 00 00 68 74 74 70 3a 2f 2f 77 77 77 2e 66 |*...http://www.f| 000000c0 65 6c 69 70 65 73 61 72 72 6f 2e 70 61 67 69 6e |elipesarro.pagin| 000000d0 61 2d 6f 66 69 63 69 61 6c 2e 63 6f 6d 00 49 53 |a-oficial.com.IS| 000000e0 46 54 0d 00 00 00 4c 61 76 66 36 31 2e 37 2e 31 |FT....Lavf61.7.1| 000000f0 30 30 00 00 64 61 74 61 00 82 5f 03 00 00 00 00 |00..data.._.....| 00000100 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
Let's see if we can make sense of this. The format begins with RIFF, followed by 4 byte and WAVE - 12 bytes in all. It is immediately followed by "fmt " (notice the space).
