Solves the full duplex problem of the mini2440 sound card and enables simultaneous recording and playback.

# Include <unistd. h> <br/> # include <fcntl. h> <br/> # include <sys/types. h> <br/> # include <sys/IOCTL. h> <br/> # include <stdlib. h> <br/> # include <stdio. h> <br/> # include <Linux/Soundcard. h> <br/> # include <pthread. h> <br/> # define length 3 <br/> # define rate 8000 <br/> # define size 8 <br/> # define Channels 1 <br/> unsigned char buf [length * rate * size * channels/8]; <br/> int main () <br/> {<br/> int fd_r, fd_w; <Br/> int ARG; <br/> int status; <br/> pid_t PID; <br/> int recing = 1, playing = 0; <br/> pid = fork (); <br/> If (PID <0) {<br/> perror ("error in fork/N "); <br/>}< br/> If (pid = 0) {<br/> fd_r = open ("/dev/DSP", o_rdonly ); <br/> If (fd_r <0) {<br/> perror ("open read of/dev/DSP failed"); <br/> exit (1 ); <br/>}</P> <p> Arg = size; <br/> Status = IOCTL (fd_r, sound_pcm_write_bits, & Arg ); <br/> If (status =-1) <br/> Per Ror ("sound_pcm_write_bits IOCTL failed"); <br/> If (Arg! = Size) <br/> perror ("unable to set sample size"); </P> <p> Arg = channels; <br/> Status = IOCTL (fd_r, sound_pcm_write_channels, & Arg); <br/> If (status =-1) <br/> perror ("sound_pcm_write_channels IOCTL failed"); <br/> If (Arg! = Channels) <br/> perror ("unable to set number of channels"); </P> <p> Arg = rate; <br/> Status = IOCTL (fd_r, sound_pcm_write_rate, & Arg); <br/> If (status =-1) <br/> perror ("sound_pcm_write_write IOCTL failed "); </P> <p> while (1) <br/> {<br/> If (playing = 0) {<br/> recing = 1; <br/> printf ("Say something:"); <br/> Status = read (fd_r, Buf, sizeof (BUF )); <br/>/* recording */<br/> If (status! = Sizeof (BUF) <br/> perror ("read wrong number of bytes"); <br/> recing = 0; <br/>}< br/> else {<br/> fd_w = open ("/dev/DSP", o_wronly ); <br/> If (fd_w <0) <br/> {<br/> perror ("Open write of/dev/DSP failed "); <br/> exit (1); <br/>}</P> <p> Arg = size; <br/> Status = IOCTL (fd_w, sound_pcm_write_bits, & Arg); <br/> If (status =-1) <br/> perror ("sound_pcm_write_bits IOCTL failed"); <br/> If (Arg! = Size) <br/> perror ("unable to set sample size"); </P> <p> Arg = channels; <br/> Status = IOCTL (fd_w, sound_pcm_write_channels, & Arg); <br/> If (status =-1) <br/> perror ("sound_pcm_write_channels IOCTL failed"); <br/> If (Arg! = Channels) <br/> perror ("unable to set number of channels"); </P> <p> Arg = rate; <br/> Status = IOCTL (fd_w, sound_pcm_write_rate, & Arg); <br/> If (status =-1) <br/> perror ("sound_pcm_write_write IOCTL failed"); <br/> while (1) <br/> {<br/> If (recing = 0) {<br/> playing = 1; <br/> Status = write (fd_w, Buf, sizeof (BUF); <br/>/* playback */<br/> If (status! = Sizeof (BUF) <br/> perror ("wrote wrong number of bytes"); <br/> Status = IOCTL (fd_w, sound_pcm_sync, 0 ); <br/> If (status =-1) <br/> perror ("sound_pcm_sync IOCTL failed"); <br/> playing = 0; <br/>}< br/>