Quick readme that's going to be here until proper documentation is made.

Echo is licensed under the zlib license. Feel free to use it as long as you
don't claim you made Echo (no credit needed though). If you modify it don't
claim it's vanilla Echo either :P

THIS CODE HAS NOT BEEN TESTED YET. I CURRENTLY DON'T HAVE ANY C DEVKIT TO
VERIFY IT WORKS FINE. I HAVE DONE AS MANY CHECKS AS POSSIBLE (AND IT
DEFINITELY SHOULD BUILD) BUT I NEED REPORTS TO KNOW IF IT'S WORKING AS
EXPECTED. SORRY FOR THE INCONVENIENCE.

=============================================================================

To include Echo in your program, you need to include echo.c, echo.h and
echoblob.h in it (and yes, you can put echo.h as a system file if you want).
That's pretty much it.

To access the Echo stuff, include echo.h in the source files that need to
make use of it. It contains all the function definitions and such, as well as
the macros needed to make the instrument list.

echoblob.h is already included here, but if you want to use a different Z80
blob from the included one, you can use the blob2c tool. It's a command line
tool and its usage is pretty simple: blob2c «input.bin» «output.c»

=============================================================================

Echo makes use of an instrument list. In the case of the C version of Echo,
you need to make a null-terminated pointer list, e.g. as follows:

const void *list[] = {
   instrument1,
   instrument2,
   instrument3,
   instrument4,
   instrument5,
   NULL
};

Where 'list' is the name the list will have. This is the same name you have
to pass to echo_init(). 'instrument1' etc. are pointers to the data of each
instrument (EIF, EEF, EWF).

If NULL isn't defined for whatever reason either include stddef.h or just use
0 instead (which is the same value).

=============================================================================

Quick overview of the functions. The functions map 1:1 to their asm
counterparts, by the way.

   echo_init(list)
   
      Initializes Echo. 'list' is a pointer to the instrument list (pass here
      the name you passed to ECHO_LIST_START). Make sure to call this before
      doing anything else with Echo.
   
   echo_play_bgm(stream)
   
      Plays background music. 'stream' is a pointer to the ESF data.
   
   echo_stop_bgm()
   
      Stops background music playback.
   
   echo_play_sfx(stream)
   
      Plays a sound effect. 'stream' is a pointer to the ESF data.
   
   echo_stop_sfx()
   
      Stops sound effect playback.
   
   echo_get_status()
   
      Gets the current status of Echo. It returns a value which is an OR of
      the following flags (as appropriate):
      
         ECHO_STAT_BGM .... Background music is playing
         ECHO_STAT_SFX .... Sound effect is playing
         ECHO_STAT_BUSY ... Echo is busy (can't parse commands yet)
      
      And just to make it clear: if you send a command to Echo while it's
      busy, it won't fail, it'll just make the 68000 wait until Echo is
      ready. No need to explicitly check for it. Check this only if you want
      to prevent the 68000 waiting.
   
   echo_send_command(command)
   
      Lets you send a raw command to Echo. Use this for commands not taking
      parameters.
   
   echo_send_command_ex(command, address)
   
      Lets you send a raw command to Echo. Use this for commands that take an
      address as a parameter.