Hi! I have just ported the pcm-sound demo to rtai. you can download it here: http://www.rcs.ei.tum.de/~kuhn/rtlinux/rtai_pcmsound-19991219.tgz maybe it is usefull for somebody Bernhard here's the README-file: Syntax: insmod pcmsound.o [soundfifo=<number-of-soundfifo>] [\ period=<period-in-nanoseconds>] [\ oversampling=<oversampling>] [\ gain=<gain>] [\ gainfifo=<number-of-gainfifo>] Decription: This demo was inspired by the original "rtl-sound demo" from Michael Barabanov, but instead of just altnating the level of the PC-speaker according to positive or negative waves (aka 1-Bit DA-Converter), here we do an oversampled pulse width modulation. As a PC-Speaker acts like a low pass filter, the disturbing base-frequence will be unhearble. Therory of operation: The sound data will not only be converted to "0" or "1" every period like it is in the original example, but into a pulse width modulated signal (PWM): value t_off t_on ==================== -127 100.0% 0.0% -126 99.6% 0.4% ... ... ... -1 50.4% 49.6% 0 50.0% 50.0% 1 49.6% 50.4% ... ... ... +126 0.4% 99.6% +127 0.0% 100.0% Consequently, sound quality is (or at least: should be) much better, maybe comparible to a DAC with 8Khz and 6 Bit - but your mealage may vary :-) Note: with a beeper, the sound is rather bad, since it doesn't act as a low-pass filter like a real speaker. Installation: Just edit the Makefile and do a "make". Then, insmod the new module and send some *.au-files to /dev/rtf0, like you would do it with the original PC-Speaker sound example included in RTL2.0: cat linux.au > /dev/rtf0 BTW: "linux.au" has rather bad quality ... so try some more files to recognice the accustical difference between /dev/audio and /dev/rtf0 (both, (RTL2.0-)sound.o and pwmsound.o). Be sure that you have write access to the fifo. Before sending a *.au-file to a fifo, check if it is in ulaw, 8KHz, mono format with "play" (is part of the sox-package): play -V <soundfile.au> Controling Volume: do a echo -ne "\040" > /dev/rtf1 # or selected gainfifo to change the volume ("\010" is nominal). --- [rtl] --- To unsubscribe: echo "unsubscribe rtl" | mail [EMAIL PROTECTED] OR echo "unsubscribe rtl <Your_email>" | mail [EMAIL PROTECTED] ---- For more information on Real-Time Linux see: http://www.rtlinux.org/~rtlinux/
