83 lines
3.5 KiB
C
83 lines
3.5 KiB
C
/* tonepcm.c — 直开 /dev/snd/pcmC0D0p 写 N 秒正弦并计时（不需要耳朵的 DAC 时钟验证）：
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* 若写 5s PCM 的墙钟 ≈5s（扣除缓冲），说明硬件时钟在走、DMA 在消费；
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* 若瞬间返回，说明硬件没在走（静音根因在时钟/电源域，不在数据）。
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* 用法: tonepcm [sec] [freq] 静态 mipsel。 */
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <time.h>
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#include <sys/ioctl.h>
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#include <sound/asound.h>
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static void pmask(struct snd_mask *m, unsigned bit) { m->bits[bit / 32] |= 1u << (bit % 32); }
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static void pivset(struct snd_interval *iv, unsigned val)
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{
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iv->min = iv->max = val; iv->integer = 1;
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iv->openmin = iv->openmax = 0; iv->empty = 0;
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}
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static long long now_ms(void)
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{
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struct timespec ts; clock_gettime(CLOCK_MONOTONIC, &ts);
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return (long long)ts.tv_sec * 1000 + ts.tv_nsec / 1000000;
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}
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int main(int argc, char **argv)
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{
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int sec = argc > 1 ? atoi(argv[1]) : 5;
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int freq = argc > 2 ? atoi(argv[2]) : 440;
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int rate = 44100, ch = 2;
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int fd = open("/dev/snd/pcmC0D0p", O_RDWR);
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if (fd < 0) { printf("open pcmC0D0p fail\n"); return 1; }
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struct snd_pcm_hw_params p;
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memset(&p, 0, sizeof p);
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pmask(&p.masks[SNDRV_PCM_HW_PARAM_ACCESS - SNDRV_PCM_HW_PARAM_FIRST_MASK],
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SNDRV_PCM_ACCESS_RW_INTERLEAVED);
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pmask(&p.masks[SNDRV_PCM_HW_PARAM_FORMAT - SNDRV_PCM_HW_PARAM_FIRST_MASK],
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SNDRV_PCM_FORMAT_S16_LE);
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pmask(&p.masks[SNDRV_PCM_HW_PARAM_SUBFORMAT - SNDRV_PCM_HW_PARAM_FIRST_MASK],
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SNDRV_PCM_SUBFORMAT_STD);
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pivset(&p.intervals[SNDRV_PCM_HW_PARAM_CHANNELS - SNDRV_PCM_HW_PARAM_FIRST_INTERVAL], ch);
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pivset(&p.intervals[SNDRV_PCM_HW_PARAM_RATE - SNDRV_PCM_HW_PARAM_FIRST_INTERVAL], rate);
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p.rmask = ~0u;
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if (ioctl(fd, SNDRV_PCM_IOCTL_HW_PARAMS, &p) != 0) { printf("HW_PARAMS fail\n"); close(fd); return 1; }
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printf("HW_PARAMS ok (rate interval now [%u,%u])\n",
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p.intervals[SNDRV_PCM_HW_PARAM_RATE - SNDRV_PCM_HW_PARAM_FIRST_INTERVAL].min,
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p.intervals[SNDRV_PCM_HW_PARAM_RATE - SNDRV_PCM_HW_PARAM_FIRST_INTERVAL].max);
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if (ioctl(fd, SNDRV_PCM_IOCTL_PREPARE, 0) != 0) { printf("PREPARE fail\n"); close(fd); return 1; }
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/* 生成 1 秒正弦（整数查表近似：简单累加相位，定点幅度 0.3 满幅） */
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int frames1s = rate;
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short *buf = malloc((size_t)frames1s * ch * 2);
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for (int i = 0; i < frames1s; i++) {
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/* 粗略正弦：三角波即可（验证用） */
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int period = rate / freq;
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int ph = i % period;
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int v = (ph < period / 2) ? (ph * 4 - period) : (3 * period - ph * 4);
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short s = (short)(v * 9830 / period); /* ~0.3 * 32767 */
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buf[i * 2] = s; buf[i * 2 + 1] = s;
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}
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long long t0 = now_ms();
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long long written = 0;
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for (int s2 = 0; s2 < sec; s2++) {
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ssize_t w = write(fd, buf, (size_t)frames1s * ch * 2);
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if (w <= 0) { printf("write fail at sec %d (ret=%zd)\n", s2, w); break; }
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written += w;
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}
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long long el = now_ms() - t0;
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long long bytes = (long long)sec * frames1s * ch * 2;
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printf("wrote %lld/%lld bytes in %lld ms (expected ~%d ms if hw clocking; instant = clock dead)\n",
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written, bytes, el, sec * 1000);
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struct snd_pcm_status st;
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memset(&st, 0, sizeof st);
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if (ioctl(fd, SNDRV_PCM_IOCTL_STATUS, &st) == 0)
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printf("STATUS: state=%d avail=%lu\n", st.state, (unsigned long)st.avail);
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close(fd);
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return 0;
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}
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