WIP: simcom2rtp bridge, interfacing SIMcom audio over USB to RTPlaforge/simcom

Change-Id: Id3f8633fae8881c2168d61732371e65eaff140ad

6 files changed, 685 insertions, 0 deletions

diff --git a/contrib/simcom2rtp/Makefile b/contrib/simcom2rtp/Makefile
new file mode 100644
index 000000000..e6b299b6e
--- /dev/null
+++ b/contrib/simcom2rtp/Makefile
@@ -0,0 +1,11 @@
+CFLAGS:= -O2 -g -Wall $(shell pkg-config --cflags libosmocore libosmotrau)
+LIBS:= $(shell pkg-config --libs libosmocore libosmotrau)
+
+all: osmo-simcom2rtp
+
+osmo-simcom2rtp: g711.o g711_table.o simcom2rtp.o
+	$(CC) $(LDFLAGS) -o $@ $^ $(LIBS)
+
+%.o: %.c
+	$(CC) $(CFLAGS) -o $@ -c $^
+
diff --git a/contrib/simcom2rtp/g711.c b/contrib/simcom2rtp/g711.c
new file mode 100644
index 000000000..7d0a73d1b
--- /dev/null
+++ b/contrib/simcom2rtp/g711.c
@@ -0,0 +1,313 @@
+/*
+ * This source code is a product of Sun Microsystems, Inc. and is provided
+ * for unrestricted use.  Users may copy or modify this source code without
+ * charge.
+ *
+ * SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING
+ * THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
+ *
+ * Sun source code is provided with no support and without any obligation on
+ * the part of Sun Microsystems, Inc. to assist in its use, correction,
+ * modification or enhancement.
+ *
+ * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
+ * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE
+ * OR ANY PART THEREOF.
+ *
+ * In no event will Sun Microsystems, Inc. be liable for any lost revenue
+ * or profits or other special, indirect and consequential damages, even if
+ * Sun has been advised of the possibility of such damages.
+ *
+ * Sun Microsystems, Inc.
+ * 2550 Garcia Avenue
+ * Mountain View, California  94043
+ */
+/*
+ * December 30, 1994:
+ * Functions linear2alaw, linear2ulaw have been updated to correctly
+ * convert unquantized 16 bit values.
+ * Tables for direct u- to A-law and A- to u-law conversions have been
+ * corrected.
+ * Borge Lindberg, Center for PersonKommunikation, Aalborg University.
+ * bli@cpk.auc.dk
+ *
+ */
+/*
+ * Downloaded from comp.speech site in Cambridge.
+ *
+ */
+
+#include "g711.h"
+
+/*
+ * g711.c
+ *
+ * u-law, A-law and linear PCM conversions.
+ * Source: http://www.speech.kth.se/cost250/refsys/latest/src/g711.c
+ */
+#define	SIGN_BIT	(0x80)		/* Sign bit for a A-law byte. */
+#define	QUANT_MASK	(0xf)		/* Quantization field mask. */
+#define	NSEGS		(8)		/* Number of A-law segments. */
+#define	SEG_SHIFT	(4)		/* Left shift for segment number. */
+#define	SEG_MASK	(0x70)		/* Segment field mask. */
+
+static short seg_aend[8] = {0x1F, 0x3F, 0x7F, 0xFF,
+			    0x1FF, 0x3FF, 0x7FF, 0xFFF};
+static short seg_uend[8] = {0x3F, 0x7F, 0xFF, 0x1FF,
+			    0x3FF, 0x7FF, 0xFFF, 0x1FFF};
+
+/* copy from CCITT G.711 specifications */
+unsigned char _u2a[128] = {			/* u- to A-law conversions */
+	1,	1,	2,	2,	3,	3,	4,	4,
+	5,	5,	6,	6,	7,	7,	8,	8,
+	9,	10,	11,	12,	13,	14,	15,	16,
+	17,	18,	19,	20,	21,	22,	23,	24,
+	25,	27,	29,	31,	33,	34,	35,	36,
+	37,	38,	39,	40,	41,	42,	43,	44,
+	46,	48,	49,	50,	51,	52,	53,	54,
+	55,	56,	57,	58,	59,	60,	61,	62,
+	64,	65,	66,	67,	68,	69,	70,	71,
+	72,	73,	74,	75,	76,	77,	78,	79,
+/* corrected:
+	81,	82,	83,	84,	85,	86,	87,	88, 
+   should be: */
+	80,	82,	83,	84,	85,	86,	87,	88,
+	89,	90,	91,	92,	93,	94,	95,	96,
+	97,	98,	99,	100,	101,	102,	103,	104,
+	105,	106,	107,	108,	109,	110,	111,	112,
+	113,	114,	115,	116,	117,	118,	119,	120,
+	121,	122,	123,	124,	125,	126,	127,	128};
+
+unsigned char _a2u[128] = {			/* A- to u-law conversions */
+	1,	3,	5,	7,	9,	11,	13,	15,
+	16,	17,	18,	19,	20,	21,	22,	23,
+	24,	25,	26,	27,	28,	29,	30,	31,
+	32,	32,	33,	33,	34,	34,	35,	35,
+	36,	37,	38,	39,	40,	41,	42,	43,
+	44,	45,	46,	47,	48,	48,	49,	49,
+	50,	51,	52,	53,	54,	55,	56,	57,
+	58,	59,	60,	61,	62,	63,	64,	64,
+	65,	66,	67,	68,	69,	70,	71,	72,
+/* corrected:
+	73,	74,	75,	76,	77,	78,	79,	79,
+   should be: */
+	73,	74,	75,	76,	77,	78,	79,	80,
+	80,	81,	82,	83,	84,	85,	86,	87,
+	88,	89,	90,	91,	92,	93,	94,	95,
+	96,	97,	98,	99,	100,	101,	102,	103,
+	104,	105,	106,	107,	108,	109,	110,	111,
+	112,	113,	114,	115,	116,	117,	118,	119,
+	120,	121,	122,	123,	124,	125,	126,	127};
+
+static short search(
+   short val,
+   short *table,
+   short size)
+{
+   short i;
+   
+   for (i = 0; i < size; i++) {
+      if (val <= *table++)
+	 return (i);
+   }
+   return (size);
+}
+
+/*
+ * linear2alaw() - Convert a 16-bit linear PCM value to 8-bit A-law
+ *
+ * linear2alaw() accepts an 16-bit integer and encodes it as A-law data.
+ *
+ *		Linear Input Code	Compressed Code
+ *	------------------------	---------------
+ *	0000000wxyza			000wxyz
+ *	0000001wxyza			001wxyz
+ *	000001wxyzab			010wxyz
+ *	00001wxyzabc			011wxyz
+ *	0001wxyzabcd			100wxyz
+ *	001wxyzabcde			101wxyz
+ *	01wxyzabcdef			110wxyz
+ *	1wxyzabcdefg			111wxyz
+ *
+ * For further information see John C. Bellamy's Digital Telephony, 1982,
+ * John Wiley & Sons, pps 98-111 and 472-476.
+ */
+unsigned char
+linear2alaw(short pcm_val)	/* 2's complement (16-bit range) */
+{
+   short	 mask;
+   short	 seg;
+   unsigned char aval;
+   
+   pcm_val = pcm_val >> 3;
+
+   if (pcm_val >= 0) {
+      mask = 0xD5;		/* sign (7th) bit = 1 */
+   } else {
+      mask = 0x55;		/* sign bit = 0 */
+      pcm_val = -pcm_val - 1;
+   }
+   
+   /* Convert the scaled magnitude to segment number. */
+   seg = search(pcm_val, seg_aend, 8);
+   
+   /* Combine the sign, segment, and quantization bits. */
+   
+   if (seg >= 8)		/* out of range, return maximum value. */
+      return (unsigned char) (0x7F ^ mask);
+   else {
+      aval = (unsigned char) seg << SEG_SHIFT;
+      if (seg < 2)
+	 aval |= (pcm_val >> 1) & QUANT_MASK;
+      else
+	 aval |= (pcm_val >> seg) & QUANT_MASK;
+      return (aval ^ mask);
+   }
+}
+
+/*
+ * alaw2linear() - Convert an A-law value to 16-bit linear PCM
+ *
+ */
+short
+alaw2linear(
+   unsigned char	a_val)
+{
+   short t;
+   short seg;
+   
+   a_val ^= 0x55;
+   
+   t = (a_val & QUANT_MASK) << 4;
+   seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;
+   switch (seg) {
+   case 0:
+      t += 8;
+      break;
+   case 1:
+      t += 0x108;
+      break;
+   default:
+      t += 0x108;
+      t <<= seg - 1;
+   }
+   return ((a_val & SIGN_BIT) ? t : -t);
+}
+
+#define	BIAS		(0x84)		/* Bias for linear code. */
+#define CLIP            8159
+
+/*
+* linear2ulaw() - Convert a linear PCM value to u-law
+*
+* In order to simplify the encoding process, the original linear magnitude
+* is biased by adding 33 which shifts the encoding range from (0 - 8158) to
+* (33 - 8191). The result can be seen in the following encoding table:
+*
+*	Biased Linear Input Code	Compressed Code
+*	------------------------	---------------
+*	00000001wxyza			000wxyz
+*	0000001wxyzab			001wxyz
+*	000001wxyzabc			010wxyz
+*	00001wxyzabcd			011wxyz
+*	0001wxyzabcde			100wxyz
+*	001wxyzabcdef			101wxyz
+*	01wxyzabcdefg			110wxyz
+*	1wxyzabcdefgh			111wxyz
+*
+* Each biased linear code has a leading 1 which identifies the segment
+* number. The value of the segment number is equal to 7 minus the number
+* of leading 0's. The quantization interval is directly available as the
+* four bits wxyz.  * The trailing bits (a - h) are ignored.
+*
+* Ordinarily the complement of the resulting code word is used for
+* transmission, and so the code word is complemented before it is returned.
+*
+* For further information see John C. Bellamy's Digital Telephony, 1982,
+* John Wiley & Sons, pps 98-111 and 472-476.
+*/
+unsigned char
+linear2ulaw(
+   short pcm_val)	/* 2's complement (16-bit range) */
+{
+   short         mask;
+   short	 seg;
+   unsigned char uval;
+   
+   /* Get the sign and the magnitude of the value. */
+   pcm_val = pcm_val >> 2;
+   if (pcm_val < 0) {
+      pcm_val = -pcm_val;
+      mask = 0x7F;
+   } else {
+      mask = 0xFF;
+   }
+   if ( pcm_val > CLIP ) pcm_val = CLIP;		/* clip the magnitude */
+   pcm_val += (BIAS >> 2);
+   
+   /* Convert the scaled magnitude to segment number. */
+   seg = search(pcm_val, seg_uend, 8);
+   
+   /*
+   * Combine the sign, segment, quantization bits;
+   * and complement the code word.
+   */
+   if (seg >= 8)		/* out of range, return maximum value. */
+      return (unsigned char) (0x7F ^ mask);
+   else {
+      uval = (unsigned char) (seg << 4) | ((pcm_val >> (seg + 1)) & 0xF);
+      return (uval ^ mask);
+   }
+   
+}
+
+/*
+ * ulaw2linear() - Convert a u-law value to 16-bit linear PCM
+ *
+ * First, a biased linear code is derived from the code word. An unbiased
+ * output can then be obtained by subtracting 33 from the biased code.
+ *
+ * Note that this function expects to be passed the complement of the
+ * original code word. This is in keeping with ISDN conventions.
+ */
+short
+ulaw2linear(
+   unsigned char	u_val)
+{
+   short t;
+   
+   /* Complement to obtain normal u-law value. */
+   u_val = ~u_val;
+   
+   /*
+    * Extract and bias the quantization bits. Then
+    * shift up by the segment number and subtract out the bias.
+    */
+   t = ((u_val & QUANT_MASK) << 3) + BIAS;
+   t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;
+   
+   return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS));
+}
+
+/* A-law to u-law conversion */
+unsigned char
+alaw2ulaw(
+   unsigned char	aval)
+{
+   aval &= 0xff;
+   return (unsigned char) ((aval & 0x80) ? (0xFF ^ _a2u[aval ^ 0xD5]) :
+	   (0x7F ^ _a2u[aval ^ 0x55]));
+}
+
+/* u-law to A-law conversion */
+unsigned char
+ulaw2alaw(
+   unsigned char	uval)
+{
+   uval &= 0xff;
+   return (unsigned char) ((uval & 0x80) ? (0xD5 ^ (_u2a[0xFF ^ uval] - 1)) :
+			   (0x55 ^ (_u2a[0x7F ^ uval] - 1)));
+}
+
+/* ---------- end of g711.c ----------------------------------------------------- */
\ No newline at end of file
diff --git a/contrib/simcom2rtp/g711.h b/contrib/simcom2rtp/g711.h
new file mode 100644
index 000000000..8bf053a0c
--- /dev/null
+++ b/contrib/simcom2rtp/g711.h
@@ -0,0 +1,27 @@
+/*
+ * g711.h
+ *
+ * u-law, A-law and linear PCM conversions.
+ * Source: http://www.speech.kth.se/cost250/refsys/latest/src/g711.h
+ */
+
+#ifndef _G711_H_
+#define _G711_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+unsigned char	linear2alaw(short pcm_val);
+short		    alaw2linear(unsigned char a_val);
+unsigned char	linear2ulaw(short pcm_val);
+short		    ulaw2linear(unsigned char u_val);
+unsigned char	alaw2ulaw(unsigned char aval);
+unsigned char	ulaw2alaw(unsigned char uval);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _G711_H_ */
\ No newline at end of file
diff --git a/contrib/simcom2rtp/g711_table.c b/contrib/simcom2rtp/g711_table.c
new file mode 100644
index 000000000..465a5705e
--- /dev/null
+++ b/contrib/simcom2rtp/g711_table.c
@@ -0,0 +1,102 @@
+#ifndef G711_TABLE_H
+#define G711_TABLE_H
+
+#include "g711.h"
+
+/* 16384 entries per table (16 bit) */
+unsigned char linear_to_alaw[65536];
+unsigned char linear_to_ulaw[65536];
+
+/* 16384 entries per table (8 bit) */
+unsigned short alaw_to_linear[256];
+unsigned short ulaw_to_linear[256];
+
+static void build_linear_to_xlaw_table(unsigned char *linear_to_xlaw,
+                                       unsigned char (*linear2xlaw)(short))
+{
+    int i;
+
+    for (i=0; i<65536;i++){
+        linear_to_xlaw[i] = linear2xlaw((short) i);
+    }
+}
+
+static void build_xlaw_to_linear_table(unsigned short *xlaw_to_linear,
+                                       short (*xlaw2linear)(unsigned char))
+{
+    int i;
+
+    for (i=0; i<256;i++){
+        xlaw_to_linear[i] = (unsigned short) xlaw2linear(i);
+    }
+}
+
+static void pcm16_to_xlaw(unsigned char *linear_to_xlaw, int src_length, const char *src_samples, char *dst_samples)
+{
+    int i;
+    const unsigned short *s_samples;
+
+    s_samples = (const unsigned short *)src_samples;
+
+    for (i=0; i < src_length / 2; i++)
+    {
+        dst_samples[i] = linear_to_xlaw[s_samples[i]];
+    }
+}
+
+static void xlaw_to_pcm16(unsigned short *xlaw_to_linear, int src_length, const char *src_samples, char *dst_samples)
+{
+    int i;
+    unsigned char *s_samples;
+    unsigned short *d_samples;
+
+    s_samples = (unsigned char *) src_samples;
+    d_samples = (unsigned short *)dst_samples;
+
+    for (i=0; i < src_length; i++)
+    {
+        d_samples[i] = xlaw_to_linear[s_samples[i]];
+    }
+}
+
+void pcm16_to_alaw(int src_length, const char *src_samples, char *dst_samples)
+{
+    pcm16_to_xlaw(linear_to_alaw, src_length, src_samples, dst_samples);
+}
+
+void pcm16_to_ulaw(int src_length, const char *src_samples, char *dst_samples)
+{
+    pcm16_to_xlaw(linear_to_ulaw, src_length, src_samples, dst_samples);
+}
+
+void alaw_to_pcm16(int src_length, const char *src_samples, char *dst_samples)
+{
+    xlaw_to_pcm16(alaw_to_linear, src_length, src_samples, dst_samples);
+}
+
+void ulaw_to_pcm16(int src_length, const char *src_samples, char *dst_samples)
+{
+    xlaw_to_pcm16(ulaw_to_linear, src_length, src_samples, dst_samples);
+}
+
+void pcm16_alaw_tableinit()
+{
+    build_linear_to_xlaw_table(linear_to_alaw, linear2alaw);
+}
+
+void pcm16_ulaw_tableinit()
+{
+    build_linear_to_xlaw_table(linear_to_ulaw, linear2ulaw);
+}
+
+void alaw_pcm16_tableinit()
+{
+    build_xlaw_to_linear_table(alaw_to_linear, alaw2linear);
+}
+
+void ulaw_pcm16_tableinit()
+{
+    build_xlaw_to_linear_table(ulaw_to_linear, ulaw2linear);
+}
+
+#endif // G711_TABLE_H
diff --git a/contrib/simcom2rtp/g711_table.h b/contrib/simcom2rtp/g711_table.h
new file mode 100644
index 000000000..2557c3b8b
--- /dev/null
+++ b/contrib/simcom2rtp/g711_table.h
@@ -0,0 +1,14 @@
+#ifndef G711_TABLE_H
+#define G711_TABLE_H
+
+void pcm16_to_alaw(int length, const char *src_samples, char *dst_samples);
+void pcm16_to_ulaw(int length, const char *src_samples, char *dst_samples);
+void alaw_to_pcm16(int length, const char *src_samples, char *dst_samples);
+void ulaw_to_pcm16(int length, const char *src_samples, char *dst_samples);
+
+void pcm16_alaw_tableinit();
+void pcm16_ulaw_tableinit();
+void alaw_pcm16_tableinit();
+void ulaw_pcm16_tableinit();
+
+#endif // G711_TABLE_H
\ No newline at end of file
diff --git a/contrib/simcom2rtp/simcom2rtp.c b/contrib/simcom2rtp/simcom2rtp.c
new file mode 100644
index 000000000..08291e243
--- /dev/null
+++ b/contrib/simcom2rtp/simcom2rtp.c
@@ -0,0 +1,218 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <limits.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+
+#include <osmocom/core/select.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/fsm.h>
+#include <osmocom/core/logging.h>
+#include <osmocom/core/application.h>
+#include <osmocom/core/serial.h>
+
+#include <osmocom/trau/osmo_ortp.h>
+
+#include "g711.h"
+
+#define RTP_PT_PCMU	0
+#define RTP_PT_PCMA	8
+
+struct modem_state {
+	struct osmo_fd data_fd;
+	struct osmo_rtp_socket *rtp;
+	/* queue of linear PCM audio in RTP -> modem direction */
+	struct llist_head rtp2modem;
+	/* message buffer used if samples insufficient for next RTP frame were received */
+	struct msgb *modem2rtp;
+};
+
+static void *g_tall_ctx;
+
+
+/* call-back on received RTP data */
+static void ortp_rx_cb(struct osmo_rtp_socket *rs, const uint8_t *payload,
+			unsigned int payload_len, uint16_t seq_nr, uint32_t timestamp, bool marker)
+{
+	/* we received a RTP frame */
+	struct modem_state *ms = rs->priv;
+	struct msgb *msg = msgb_alloc(payload_len*2, "RTP Rx");
+	unsigned int i;
+	int16_t *out;
+
+	OSMO_ASSERT(msg);
+
+	out = (int16_t *) msgb_put(msg, payload_len*2);
+
+	if (payload_len != 160) {
+		fprintf(stderr, "RTP payload length %d != 160, dropping\n", payload_len);
+		msgb_free(msg);
+		return;
+	}
+
+	/* convert from Alaw to linear PCM (160 -> 320 bytes) */
+	for (i = 0; i < payload_len; i++)
+		out[i] = alaw2linear(payload[i]);
+
+	/* append to the write queue */
+	msgb_enqueue(&ms->rtp2modem, msg);
+	ms->data_fd.when |= OSMO_FD_WRITE;
+}
+
+static void modem2rtp(struct modem_state *ms, const uint8_t *data, unsigned int len)
+{
+	const int16_t *data16 = (const int16_t *)data;
+	unsigned int samples = len / 2;
+	unsigned int offset = 0;
+	unsigned int i;
+
+	/* samples are always 16bit, we cannot read half a sample */
+	OSMO_ASSERT((len & 1) == 0);
+
+	/* first complete any pending incomplete RTP frame */
+	if (ms->modem2rtp) {
+		struct msgb *msg = ms->modem2rtp;
+		unsigned int missing_samples = 160 - msgb_length(msg);
+		for (i = 0; i < missing_samples; i++) {
+			if (i >= samples)
+				break;
+			msgb_put_u8(msg, linear2alaw(data16[i]));
+		}
+		offset = i;
+		if (msgb_length(msg) == 160) {
+			osmo_rtp_send_frame_ext(ms->rtp, msgb_data(msg), msgb_length(msg), 160, false);
+			msgb_free(msg);
+		}
+	}
+
+	/* then send as many RTP frames as we have samples */
+	for (offset = offset; offset + 160 <= samples; offset += 160) {
+		uint8_t buf[160];
+		for (i = 0; i < sizeof(buf); i++)
+			buf[i] = linear2alaw(data16[offset + i]);
+		osmo_rtp_send_frame_ext(ms->rtp, buf, sizeof(buf), 160, false);
+	}
+
+	/* store remainder in msgb */
+	if (offset < samples) {
+		struct msgb *msg = msgb_alloc_c(ms, 160, "modem2rtp");
+		OSMO_ASSERT(msg);
+		OSMO_ASSERT(len - offset < 160);
+		for (i = 0; i < len - offset; i++)
+			msgb_put_u8(msg, linear2alaw(data16[offset + i]));
+		ms->modem2rtp = msg;
+	}
+}
+
+
+/* call back on file descriptor events of the modem DATA ttyUSB device */
+static int modem_data_fd_cb(struct osmo_fd *ofd, unsigned int what)
+{
+	struct modem_state *ms = ofd->data;
+	int rc;
+
+	if (what & OSMO_FD_READ) {
+		/* SIM5360 USB AUDIO Application Note v1.01 states 1600 bytes every 100ms */
+		uint8_t rx_buf[1600];
+		rc = read(ofd->fd, rx_buf, sizeof(rx_buf));
+		OSMO_ASSERT(rc > 0);
+		modem2rtp(ms, rx_buf, rc);
+	}
+
+	if (what & OSMO_FD_WRITE) {
+		struct msgb *msg = msgb_dequeue(&ms->rtp2modem);
+		if (!msg)
+			ofd->when &= ~OSMO_FD_WRITE;
+		else {
+			/* SIM5300 USB AUDIO Application Note v1.01 states 640 bytes every 40ms;
+			 * we simply write every RTP frame individually (320 bytes every 20ms) */
+			rc = write(ofd->fd, msgb_data(msg), msgb_length(msg));
+			if (rc != msgb_length(msg))
+				fprintf(stderr, "Short write: %d < %u\n", rc, msgb_length(msg));
+			msgb_free(msg);
+		}
+	}
+
+	return 0;
+}
+
+
+static int modem_data_open(struct modem_state *ms, const char *basepath)
+{
+	char fname[PATH_MAX+1];
+	int fd;
+
+	/* the assumption is that the caller provides something like
+	 * "/dev/serial/by-path/pci-0000:00:14.0-usb-0:2:1" */
+	snprintf(fname, sizeof(fname), "%s.0-port0", basepath);
+
+	fd = osmo_serial_init(fname, 921600);
+	if (fd < 0) {
+		fprintf(stderr, "failed to open device '%s': %s\n", fname, strerror(errno));
+		return -1;
+	}
+	osmo_fd_setup(&ms->data_fd, fd, OSMO_FD_READ, modem_data_fd_cb, ms, 0);
+	osmo_fd_register(&ms->data_fd);
+
+	return 0;
+}
+
+static struct modem_state *modem_create(void *ctx)
+{
+	struct modem_state *ms = talloc_zero(ctx, struct modem_state);
+	int rc;
+
+	INIT_LLIST_HEAD(&ms->rtp2modem);
+
+	ms->rtp = osmo_rtp_socket_create(ms, 0);
+	OSMO_ASSERT(ms->rtp);
+	osmo_rtp_socket_set_pt(ms->rtp, RTP_PT_PCMA);
+	ms->rtp->priv = ms;
+	ms->rtp->rx_cb = ortp_rx_cb;
+
+	rc = osmo_rtp_socket_bind(ms->rtp, "0.0.0.0", 1111);
+	OSMO_ASSERT(rc == 0);
+
+	rc = osmo_rtp_socket_connect(ms->rtp, "127.0.0.1", 2222);
+	//rc = osmo_rtp_socket_autoconnect(ms->rtp);
+	OSMO_ASSERT(rc == 0);
+
+	osmo_rtp_set_source_desc(ms->rtp, "cname", "simcom2rtp", NULL, NULL, NULL,
+				 "osmo-simcom2rtp", NULL);
+
+	return ms;
+}
+
+
+
+
+int main(int argc, char **argv)
+{
+
+	talloc_enable_null_tracking();
+	g_tall_ctx = talloc_named_const(NULL, 1, "simcom2rtp");
+
+	msgb_talloc_ctx_init(g_tall_ctx, 0);
+	osmo_init_logging2(g_tall_ctx, NULL);
+	osmo_fsm_log_timeouts(true);
+	osmo_fsm_log_addr(true);
+	//osmo_stats_init(g_tall_ctx);
+	osmo_rtp_init(g_tall_ctx);
+
+	struct modem_state *ms = modem_create(g_tall_ctx);
+	int rc;
+
+	OSMO_ASSERT(ms);
+	rc = modem_data_open(ms, "/dev/serial/by-path/pci-0000:00:14.0-usb-0:2:1");
+	OSMO_ASSERT(rc == 0);
+
+	while (1) {
+		osmo_select_main(0);
+	}
+
+}