120 lines
3.2 KiB
C
120 lines
3.2 KiB
C
// serial_to_wav.c
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <termios.h>
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#include <signal.h>
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#define SERIAL_PORT "/dev/ttyESP32_A"
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#define BAUD_RATE B1500000
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#define RATE 16000
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#define CHANNELS 2
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#define BPS 16
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#define BLOCK_SIZE 512 // PCM bytes per block (128 stereo frames)
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#define MAGIC 0xABCD // header marker
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static volatile sig_atomic_t stop_flag = 0;
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void on_sigint(int sig) { (void)sig; stop_flag = 1; }
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void write_wav_header(FILE *f, uint32_t data_bytes) {
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uint32_t byte_rate = RATE * CHANNELS * (BPS/8);
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uint16_t block_align = CHANNELS * (BPS/8);
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uint32_t riff_size = 36 + data_bytes;
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fseek(f, 0, SEEK_SET);
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fwrite("RIFF", 1, 4, f);
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fwrite(&riff_size, 4, 1, f);
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fwrite("WAVE", 1, 4, f);
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fwrite("fmt ", 1, 4, f);
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uint32_t fmt_size = 16;
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fwrite(&fmt_size, 4, 1, f);
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uint16_t audio_fmt = 1;
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fwrite(&audio_fmt, 2, 1, f);
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uint16_t ch = CHANNELS;
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fwrite(&ch, 2, 1, f);
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uint32_t sr = RATE;
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fwrite(&sr, 4, 1, f);
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fwrite(&byte_rate, 4, 1, f);
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fwrite(&block_align, 2, 1, f);
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uint16_t bits = BPS;
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fwrite(&bits, 2, 1, f);
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fwrite("data", 1, 4, f);
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fwrite(&data_bytes, 4, 1, f);
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}
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int open_serial(const char *path) {
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int fd = open(path, O_RDONLY | O_NOCTTY);
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if (fd < 0) { perror("open"); return -1; }
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struct termios tio;
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if (tcgetattr(fd, &tio) != 0) { perror("tcgetattr"); close(fd); return -1; }
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cfsetispeed(&tio, BAUD_RATE);
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cfsetospeed(&tio, BAUD_RATE);
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tio.c_iflag &= ~(IGNBRK | BRKINT | ICRNL | INLCR | IXON | IXOFF | IXANY |
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PARMRK | INPCK | ISTRIP);
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tio.c_oflag &= ~(OPOST);
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tio.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN | ISIG);
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tio.c_cflag &= ~(CSIZE | PARENB | CSTOPB | CRTSCTS);
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tio.c_cflag |= (CS8 | CLOCAL | CREAD);
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tio.c_cc[VMIN] = 1;
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tio.c_cc[VTIME] = 0;
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if (tcsetattr(fd, TCSANOW, &tio) != 0) { perror("tcsetattr"); close(fd); return -1; }
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return fd;
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}
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int main() {
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signal(SIGINT, on_sigint);
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int fd = open_serial(SERIAL_PORT);
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if (fd < 0) return 1;
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FILE *out = fopen("capture.wav", "wb+");
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if (!out) { perror("fopen"); close(fd); return 1; }
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uint32_t data_bytes = 0;
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fseek(out, 44, SEEK_SET);
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while (!stop_flag) {
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// Read header bytes explicitly
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uint8_t hbuf[2];
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ssize_t hn = read(fd, hbuf, 2);
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if (hn != 2) continue;
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uint16_t hdr = hbuf[0] | (hbuf[1] << 8); // little-endian decode
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if (hdr != MAGIC) {
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// Not aligned, skip one byte and retry
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continue;
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}
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// Accumulate one full PCM block
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uint8_t block[BLOCK_SIZE];
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size_t got = 0;
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while (got < BLOCK_SIZE && !stop_flag) {
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ssize_t m = read(fd, block + got, BLOCK_SIZE - got);
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if (m > 0) got += (size_t)m;
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}
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if (got == BLOCK_SIZE) {
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fwrite(block, 1, BLOCK_SIZE, out);
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data_bytes += BLOCK_SIZE;
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}
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}
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write_wav_header(out, data_bytes);
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fflush(out);
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fclose(out);
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close(fd);
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fprintf(stderr, "Saved capture.wav with %u bytes of audio\n", data_bytes);
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return 0;
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}
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