how to create sound effect with library TONES.C

[rald]

Hello everyone,

I have a big problems to create sound effect with a PIC, I am using 12F683 and I need to save into this one a laser effect, however, I have the problem that I can't use a wav file because the memory size is so small that I can use it, my idea is to create the same sound effect with tones but I have not idea how to do it?

please, tell me that someone knows how to help me this?

I am desperate!!!!!! HELP please........

thanks

[Mike Walne]

CCS has provided the software (EX_TONES.C).

How do you propose to use the hardware you've not told us about?

Mike

[Ttelmah]

You need to also understand a lot about sounds.

The point about 'tones', is it keeps the space for the sounds generated small, by only generating simple single tone 'notes', each for a period of time. So all it has to store is a table of 'note', and 'time' values. Ideal for simple little tunes like 'happy birthday'. So, sequential monophonic tones. Some 'sound effects', can be completely unsuitable to generate this way. A 'simple' 'swoosh' sound, requires a section of effectively a white noise signal, with the actual selected output frequencies of this being changed. A noise like this cannot be generated by tones.c, and would probably require several KB of storage for any practical system...

So the amount of storage needed depends totally on the type of sound required. Since laser's, don't actually make a noise at all, visualising what you want gets hard. The noises used for lasers in most sci-fi type games, are noise based, not difficult for a little chip like this to produce.

Place to look is in the noise effects from the very first generation of electronic games machines. If you look at SpaceWar (one of the earliest games):
<http://scratch.mit.edu/projects/14086159/>
Turn off music, and try the laser, this is a sequence of very short notes, starting high, and dropping to produce the sound, then followed by a longer low note tailing away when the laser button is released. Just try a sequence of notes in tones, making each short (about 1/10th the duration of the shortest in the example), and going down the music scale, and see what it sounds like.

[RoGuE_StreaK]

How set are you on the 12F683? If the sound is an integral part of your project, I'd suggest going for something with enough memory.

That said, you should have enough room for a couple of sampled waveforms, at say 8bit 16kHz (or less kHz for less size), use a table to dictate how many times each sample loops and what amplitude it should run at; some math can reduce the volume if feeding directly into PWM, depends on how much of a performance hit you want. Maybe someone knows of a clever way of using bitwise operations to halve / quarter the volume?

You can run two 7bit samples and add them together to get an 8bit mix for a dual-oscillator effect.

But as Ttelmah says, you need to understand a lot about sounds, and sampling, to pull it off. In a way I'm lucky that my first sampling keyboard was an 8bit beast with extremely limited memory, it forced you to really understand the nitty-gritty to get anything usable out of it.

[ELCouz]