Audio via USART (STM32F4 Discovery)

[sgardner661]

Posted on May 07, 2013 at 03:07

I'm trying to create a project where I send an audio file from a computer to my STM32F4-Discovery board via USART and play the file. I have successfully run a USART example where a character is sent to the F4 board and back to the computer. I have also run a program where a mp3 file stored in flash memory is played.

I was wondering how I could integrate the two programs. The mp3 used in the program is actually an mp3 file that was converted into a series of hex characters (c array). How would I send that c array to the F4 board?Here's the mp3 program I used:

http://vedder.se/2012/07/play-mp3-on-the-stm32f4-discovery/

#usart #mp3 #stm32f4 #uart #xmodem #audio

[Tesla DeLorean]

Posted on May 07, 2013 at 04:04

The mp3 used in the program is actually an mp3 file that was converted into a series of hex characters (c array). How would I send that c array to the F4 board?

Why wouldn't you just send the unconverted binary data as 8-bit data over the serial port? RealTerm - Send File? Accumulate the bytes at the receiving end and send off to the MP3 player. Not sure you have the bandwidth.

[sgardner661]

Posted on May 07, 2013 at 07:25

I've never used Realterm before, so can I send an mp3 file as is over the serial port?

[Andrew Neil]

Posted on May 07, 2013 at 12:06

Probably best to use a protocol such as XMODEM.

Any decent terminal app (even Hyperterminal) and many comms toolkits can do XMODEM. The ST In-Application Programming (IAP) App Note uses XMODEM - so you have a ready example there (not a very good implementation, but it does work).

[Tesla DeLorean]

Posted on May 07, 2013 at 13:46

I've never used Realterm before, so can I send an mp3 file as is over the serial port?

What is an MP3 file composed of? A stream of bytes. The serial port can transmit said bytes. XMODEM would add a protocol layer to ensure the data arrives correctly, by potentially retrying corrupt blocks.

[sgardner661]

Posted on May 07, 2013 at 20:28

Ok I'm going to start working on that. By the way how would I find out if I have the bandwidth capabilities to perform this task? Is that referring to a limitation of the F4 board?

[Tesla DeLorean]

Posted on May 07, 2013 at 21:56

By the way how would I find out if I have the bandwidth capabilities to perform this task? Is that referring to a limitation of the F4 board?

A 128 Kbps MP3 will not fit down a pipe at 115200 baud.

[sgardner661]

Posted on May 08, 2013 at 05:36

Ahh ok well thanks for the help