80 lines
2.1 KiB
C++
80 lines
2.1 KiB
C++
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#include "pcmdma.h"
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#include <pthread.h>
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#include <alsa/asoundlib.h>
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#include <signal.h>
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struct Sample {
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short l;
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short r;
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}__attribute__((packed));
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static constexpr unsigned BufLen = FULL_LEN;
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static const char *device = "default";
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static snd_pcm_t *handle;
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static int open_alsa_device (int channels, int srate) {
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int err;
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if ((err = snd_pcm_open(&handle, device, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
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printf("Playback open error: %s\n", snd_strerror(err));
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return 0;
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}
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if ((err = snd_pcm_set_params(handle,
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SND_PCM_FORMAT_S16_LE,
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SND_PCM_ACCESS_RW_INTERLEAVED,
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channels,
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srate,
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1,
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500000)) < 0) { /* 0.5sec */
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printf("Playback open error: %s\n", snd_strerror(err));
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return 0;
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}
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return 1;
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}
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int alsa_write (const void * buf, int len) {
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snd_pcm_sframes_t frames;
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int err = 0;
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frames = snd_pcm_writei(handle, buf, len);
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if (frames < 0)
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frames = snd_pcm_recover(handle, frames, 0);
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if (frames < 0) {
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printf("snd_pcm_writei failed: %s\n", snd_strerror(err));
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return 0;
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}
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if (frames > 0 && frames < (long)sizeof(buf))
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printf("Short write (expected %i, wrote %li)\n", len, frames);
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return len;
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}
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void sig_handler (int signum) {
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printf(" - Received signal %d\n", signum);
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::exit (0);
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}
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static constexpr int CC = MAXPWM / 2;
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static pthread_t rc;
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void * WriteHandler (void * data) {
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printf ("Start thread\n");
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PcmDma * pA = (PcmDma *) data;
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Sample buf [BufLen];
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uint16_t * pbuf = pA->getBuff();
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for (;;) {
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pA->send (false);
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pA->send (true);
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//printf ("pass\n");
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for (unsigned i=0; i<BufLen; i++) {
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const short s = (pbuf [i] - CC) * 10;
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buf[i].l = s; buf[i].r = s;
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}
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alsa_write (buf, BufLen);
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}
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return NULL;
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}
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PcmDma::PcmDma() noexcept : pL(buffer), pH(buffer + HALF_LEN), src(nullptr) {
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signal (SIGINT, sig_handler);
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open_alsa_device(2, 24000);
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pthread_create (&rc, NULL, WriteHandler, this);
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}
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