--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/pcm/pcm_tx.c	Sun Jun 23 19:21:00 2024 +0000
@@ -0,0 +1,56 @@
+/*
+ * In this module we implement PCM Tx toward the TRAU.
+ */
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <osmocom/core/select.h>
+
+#include "globals.h"
+
+static const uint8_t dmw_alaw[8] =
+	{0x34, 0x21, 0x21, 0x34, 0xB4, 0xA1, 0xA1, 0xB4};
+
+static uint8_t pcm_fill_octet = 0x54;
+static bool dmw_active;
+static uint8_t *play_buffer;
+static unsigned play_buf_nframes, play_buf_ptr;
+
+static void fill_with_dmw(uint8_t *buf)
+{
+	unsigned n;
+
+	for (n = 0; n < 20; n++) {
+		memcpy(buf, dmw_alaw, 8);
+		buf += 8;
+	}
+}
+
+static void fill_with_play(uint8_t *outbuf)
+{
+	memcpy(outbuf, play_buffer + play_buf_ptr * 160, 160);
+	play_buf_ptr++;
+	if (play_buf_ptr < play_buf_nframes)
+		return;
+	free(play_buffer);
+	play_buffer = 0;
+	printf("file play finished\n");
+}
+
+void transmit_pcm_20ms(void)
+{
+	uint8_t buf[160];
+
+	if (play_buffer)
+		fill_with_play(buf);
+	else if (dmw_active)
+		fill_with_dmw(buf);
+	else
+		memset(buf, pcm_fill_octet, 160);
+	write(ts_fd, buf, 160);
+}