diff --git a/src/Makefile b/src/Makefile
index 221da15..6580c1a 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -6,10 +6,10 @@
 %.o: %.c
 	$(CC) $(CFLAGS) -o $@ -c $^
 
-e1_test: osmo_e1.o crc4itu.o e1_test.o
+e1_test: osmo_e1f.o crc4itu.o e1_test.o
 	$(CC) $(LDFLAGS) -o $@ $^
 
-e1_test_dieter: osmo_e1.o crc4itu.o e1_test_dieter.o
+e1_test_dieter: osmo_e1f.o crc4itu.o e1_test_dieter.o
 	$(CC) $(LDFLAGS) -o $@ $^
 
 
diff --git a/src/e1_test.c b/src/e1_test.c
index c6d0e22..cd0bf87 100644
--- a/src/e1_test.c
+++ b/src/e1_test.c
@@ -9,29 +9,29 @@
 #include <osmocom/core/application.h>
 #include <osmocom/gsm/gsm_utils.h>
 
-#include "osmo_e1.h"
+#include "osmo_e1f.h"
 
-static struct osmo_e1_instance inst;
+static struct osmo_e1f_instance inst;
 static struct log_info log_info = {};
 
 /* pull data out of the transmitter and print hexdumps */
-static void pull_and_print(struct osmo_e1_instance *e1i)
+static void pull_and_print(struct osmo_e1f_instance *e1i)
 {
 	uint8_t buf[32];
-	osmo_e1_pull_tx_frame(e1i, buf);
+	osmo_e1f_pull_tx_frame(e1i, buf);
 	printf("%s\n", osmo_hexdump(buf, sizeof(buf)));
 }
 
-static void data_cb(struct osmo_e1_instance_ts *e1t, struct msgb *msg)
+static void data_cb(struct osmo_e1f_instance_ts *e1t, struct msgb *msg)
 {
 	printf("Rx TS %u: %s\n", e1t->ts_nr, msgb_hexdump(msg));
 	msgb_free(msg);
 }
 
-static void notify_cb(struct osmo_e1_instance *e1i, enum osmo_e1_notify_event evt,
+static void notify_cb(struct osmo_e1f_instance *e1i, enum osmo_e1f_notify_event evt,
 			bool present, void *data)
 {
-	printf("NOTIFY: %s %s\n", osmo_e1_notify_event_name(evt), present ? "PRESENT" : "ABSENT");
+	printf("NOTIFY: %s %s\n", osmo_e1f_notify_event_name(evt), present ? "PRESENT" : "ABSENT");
 }
 
 /* feed some random data into the E1 instance */
@@ -42,7 +42,7 @@
 
 	for (i = 0; i < 200; i++) {
 		osmo_get_rand_id(buf, sizeof(buf));
-		osmo_e1_rx_frame(&inst, buf);
+		osmo_e1f_rx_frame(&inst, buf);
 	}
 }
 
@@ -61,7 +61,7 @@
 			buf[0] = 0x40;
 			break;
 		}
-		osmo_e1_rx_frame(&inst, buf);
+		osmo_e1f_rx_frame(&inst, buf);
 	}
 }
 
@@ -96,7 +96,7 @@
 			buf[0] = 0xc0;
 			break;
 		}
-		osmo_e1_rx_frame(&inst, buf);
+		osmo_e1f_rx_frame(&inst, buf);
 	}
 }
 
@@ -114,28 +114,28 @@
 	int i;
 
 	osmo_init_logging2(NULL, &log_info);
-	osmo_e1_init();
+	osmo_e1f_init();
 
-	osmo_e1_instance_init(&inst, "e1_test", &notify_cb, true, NULL);
+	osmo_e1f_instance_init(&inst, "e1_test", &notify_cb, true, NULL);
 	for (i = 1; i < 32; i++) {
-		struct osmo_e1_instance_ts *e1t = osmo_e1_instance_ts(&inst, i);
-		osmo_e1_ts_config(e1t, &data_cb, 40, true, OSMO_E1_TS_RAW);
+		struct osmo_e1f_instance_ts *e1t = osmo_e1f_instance_ts(&inst, i);
+		osmo_e1f_ts_config(e1t, &data_cb, 40, true, OSMO_E1F_TS_RAW);
 	}
 
 	printf("\nRx Random...\n");
-	osmo_e1_instance_reset(&inst);
+	osmo_e1f_instance_reset(&inst);
 	tc_rx_random();
 
 	printf("\nAlign (Basic)...\n");
-	osmo_e1_instance_reset(&inst);
+	osmo_e1f_instance_reset(&inst);
 	tc_rx_align_basic();
 
 	printf("\nAlign (Mframe)...\n");
-	osmo_e1_instance_reset(&inst);
+	osmo_e1f_instance_reset(&inst);
 	tc_rx_align_mframe();
 
 	printf("\nTX Idle...\n");
-	osmo_e1_instance_reset(&inst);
+	osmo_e1f_instance_reset(&inst);
 	tc_tx_idle();
 
 }
diff --git a/src/e1_test_dieter.c b/src/e1_test_dieter.c
index 6277556..62334e4 100644
--- a/src/e1_test_dieter.c
+++ b/src/e1_test_dieter.c
@@ -11,21 +11,21 @@
 #include <osmocom/core/application.h>
 #include <osmocom/gsm/gsm_utils.h>
 
-#include "osmo_e1.h"
+#include "osmo_e1f.h"
 
-static struct osmo_e1_instance inst;
+static struct osmo_e1f_instance inst;
 static struct log_info log_info = {};
 
-static void data_cb(struct osmo_e1_instance_ts *e1t, struct msgb *msg)
+static void data_cb(struct osmo_e1f_instance_ts *e1t, struct msgb *msg)
 {
 	printf("Rx TS %02u: %s\n", e1t->ts_nr, msgb_hexdump(msg));
 	msgb_free(msg);
 }
 
-static void notify_cb(struct osmo_e1_instance *e1i, enum osmo_e1_notify_event evt,
+static void notify_cb(struct osmo_e1f_instance *e1i, enum osmo_e1f_notify_event evt,
 			bool present, void *data)
 {
-	fprintf(stdout, "NOTIFY: %s %s\n", osmo_e1_notify_event_name(evt), present ? "PRESENT" : "ABSENT");
+	fprintf(stdout, "NOTIFY: %s %s\n", osmo_e1f_notify_event_name(evt), present ? "PRESENT" : "ABSENT");
 }
 
 static void read_file(const char *fname)
@@ -45,7 +45,7 @@
 		if (rc < sizeof(buf))
 			exit(24);
 		//printf("FRAME: %s\n", osmo_hexdump(buf, sizeof(buf)));
-		osmo_e1_rx_frame(&inst, buf);
+		osmo_e1f_rx_frame(&inst, buf);
 	}
 }
 
@@ -54,16 +54,16 @@
 	int i;
 
 	osmo_init_logging2(NULL, &log_info);
-	osmo_e1_init();
+	osmo_e1f_init();
 
-	osmo_e1_instance_init(&inst, "e1_test", &notify_cb, true, NULL);
+	osmo_e1f_instance_init(&inst, "e1_test", &notify_cb, true, NULL);
 	for (i = 1; i < 32; i++) {
-		struct osmo_e1_instance_ts *e1t = osmo_e1_instance_ts(&inst, i);
-		enum osmo_e1_ts_mode mode;
+		struct osmo_e1f_instance_ts *e1t = osmo_e1f_instance_ts(&inst, i);
+		enum osmo_e1f_ts_mode mode;
 		bool enable;
 		switch (i) {
 		case 2:
-			mode = OSMO_E1_TS_HDLC_CRC;
+			mode = OSMO_E1F_TS_HDLC_CRC;
 			enable = true;
 			break;
 		case 5:
@@ -71,11 +71,11 @@
 		case 7:
 		case 8:
 		default:
-			mode = OSMO_E1_TS_RAW;
+			mode = OSMO_E1F_TS_RAW;
 			enable = false;
 			break;
 		}
-		osmo_e1_ts_config(e1t, &data_cb, 64, enable, mode);
+		osmo_e1f_ts_config(e1t, &data_cb, 64, enable, mode);
 	}
 
 	read_file("Insite_to_Racal_E1.bin");
diff --git a/src/osmo_e1.h b/src/osmo_e1.h
deleted file mode 100644
index 4f5a18a..0000000
--- a/src/osmo_e1.h
+++ /dev/null
@@ -1,122 +0,0 @@
-#pragma once
-
-#include <stdint.h>
-#include <stdbool.h>
-#include <osmocom/core/msgb.h>
-#include <osmocom/core/linuxlist.h>
-#include <osmocom/core/fsm.h>
-#include <osmocom/core/isdnhdlc.h>
-
-struct osmo_e1_tx_state {
-	bool remote_alarm;
-	bool crc4_error;
-	/* lower 5 bits: Sa4..Sa8 */
-	uint8_t sa4_sa8;
-	/* frame number 0..15 */
-	uint8_t frame_nr;
-	uint8_t crc4_last_smf;
-	uint8_t crc4;
-};
-
-struct osmo_e1_rx_state {
-	uint8_t frame_nr;
-	/* history of rceived TS0 octets */
-	uint8_t ts0_history[16];
-	uint8_t ts0_hist_len;
-	/* was a remote alarm received? */
-	bool remote_alarm;
-	bool remote_crc4_error;
-	/* number of TS0 bytes received since entering CRC mframe search */
-	uint8_t num_ts0_in_mframe_search;
-	struct osmo_fsm_inst *fi;
-	/* computed CRC4 */
-	uint8_t crc4_last_smf;
-	uint8_t crc4;
-};
-
-enum osmo_e1_notify_event {
-	E1_NTFY_EVT_ALIGN_FRAME,
-	E1_NTFY_EVT_ALIGN_CRC_MFRAME,
-	E1_NTFY_EVT_CRC_ERROR,
-	E1_NTFY_EVT_REMOTE_CRC_ERROR,
-	E1_NTFY_EVT_REMOTE_ALARM,
-};
-
-enum osmo_e1_ts_mode {
-       OSMO_E1_TS_RAW,
-       OSMO_E1_TS_HDLC_CRC,
-};
-
-struct osmo_e1_instance_ts;
-struct osmo_e1_instance;
-typedef void (*e1_data_cb)(struct osmo_e1_instance_ts *ts, struct msgb *msg);
-typedef void (*e1_notify_cb)(struct osmo_e1_instance *e1i, enum osmo_e1_notify_event evt,
-			     bool present, void *data);
-
-struct osmo_e1_instance_ts {
-	/* timeslot number */
-	uint8_t ts_nr;
-	/* mode in which we operate (RAW/HDLC) */
-	enum osmo_e1_ts_mode mode;
-	/* back-pointer to e1 instance */
-	struct osmo_e1_instance *inst;
-	struct {
-		/* optional HDLC encoder state */
-		struct osmo_isdnhdlc_vars hdlc;
-		/* queue of pending to-be-transmitted messages */
-		struct llist_head queue;
-		unsigned long underruns;
-	} tx;
-	struct {
-		/* optional HDLC decoder state */
-		struct osmo_isdnhdlc_vars hdlc;
-		bool enabled;
-		/* how many bytes to buffer before calling call-back */
-		unsigned int granularity;
-		/* current receive buffer */
-		struct msgb *msg;
-		e1_data_cb data_cb;
-		/* private data, relevant to user */
-		void *priv;
-	} rx;
-};
-
-struct osmo_e1_instance {
-	/* list; currently not used yet */
-	struct llist_head list;
-
-	/* is CRC4 generation + parsing enabled? */
-	bool crc4_enabled;
-	/* notification call-back function */
-	e1_notify_cb notify_cb;
-
-	/* Rx + Tx related state */
-	struct osmo_e1_tx_state tx;
-	struct osmo_e1_rx_state rx;
-
-	/* our 32 timeslots (only 1..32 are used) */
-	struct osmo_e1_instance_ts ts[32];
-
-	/* private data, relevant to user */
-	void *priv;
-};
-
-extern const struct value_string osmo_e1_notifv_evt_names[];
-
-static inline const char *osmo_e1_notify_event_name(enum osmo_e1_notify_event evt) {
-	return get_value_string(osmo_e1_notifv_evt_names, evt);
-}
-
-int osmo_e1_init(void);
-struct osmo_e1_instance_ts *osmo_e1_instance_ts(struct osmo_e1_instance *e1i, uint8_t ts_nr);
-int osmo_e1_instance_init(struct osmo_e1_instance *e1i, const char *name, e1_notify_cb cb,
-			  bool crc4_enabled, void *priv);
-void osmo_e1_instance_reset(struct osmo_e1_instance *e1i);
-int osmo_e1_ts_config(struct osmo_e1_instance_ts *e1t, e1_data_cb cb, unsigned int granularity,
-		      bool enable, enum osmo_e1_ts_mode mode);
-void osmo_e1_ts_reset(struct osmo_e1_instance_ts *e1t);
-
-
-void osmo_e1_ts_enqueue(struct osmo_e1_instance_ts *e1t, struct msgb *msg);
-int osmo_e1_pull_tx_frame(struct osmo_e1_instance *e1i, uint8_t *out_frame);
-int osmo_e1_rx_frame(struct osmo_e1_instance *e1i, const uint8_t *in_frame);
diff --git a/src/osmo_e1.c b/src/osmo_e1f.c
similarity index 85%
rename from src/osmo_e1.c
rename to src/osmo_e1f.c
index 2b83622..5ea6d54 100644
--- a/src/osmo_e1.c
+++ b/src/osmo_e1f.c
@@ -17,7 +17,7 @@
 #include <osmocom/core/fsm.h>
 
 #include "crc4itu.h"
-#include "osmo_e1.h"
+#include "osmo_e1f.h"
 
 #define S(x)	(1 << (x))
 
@@ -32,16 +32,16 @@
 }
 
 /* are we in SMF II (true) or I (false) */
-static inline bool is_smf_II(const struct osmo_e1_tx_state *tx) {
+static inline bool is_smf_II(const struct osmo_e1f_tx_state *tx) {
 	if (tx->frame_nr >= 8)
 		return true;
 	return false;
 }
 
 static struct osmo_fsm e1_align_fsm;
-static void align_fsm_reset(struct osmo_e1_instance *e1i);
+static void align_fsm_reset(struct osmo_e1f_instance *e1i);
 
-static void notify_user(struct osmo_e1_instance *e1i, enum osmo_e1_notify_event evt,
+static void notify_user(struct osmo_e1f_instance *e1i, enum osmo_e1f_notify_event evt,
 			bool present, void *priv)
 {
 	if (!e1i->notify_cb)
@@ -52,7 +52,7 @@
 /*! Initialize a (caller-allocated) Osmocom E1 Instance
  *  \param[inout] e1i E1 Instance to be initialized
  *  \returns 0 on success, negative on error */
-int osmo_e1_instance_init(struct osmo_e1_instance *e1i, const char *name, e1_notify_cb cb,
+int osmo_e1f_instance_init(struct osmo_e1f_instance *e1i, const char *name, e1_notify_cb cb,
 			  bool crc4_enabled, void *priv)
 {
 	int i;
@@ -64,7 +64,7 @@
 	e1i->priv = priv;
 
 	for (i = 1; i < ARRAY_SIZE(e1i->ts); i++) {
-		struct osmo_e1_instance_ts *e1t = &e1i->ts[i];
+		struct osmo_e1f_instance_ts *e1t = &e1i->ts[i];
 		e1t->ts_nr = i;
 		e1t->inst = e1i;
 		INIT_LLIST_HEAD(&e1t->tx.queue);
@@ -76,14 +76,14 @@
 	if (!e1i->rx.fi)
 		return -1;
 
-	osmo_e1_instance_reset(e1i);
+	osmo_e1f_instance_reset(e1i);
 
 	return 0;
 }
 
 /*! stop E1 timeslot; release any pending rx/tx buffers
  *  \param[in] e1t Timeslot which we are to stop, disable and release buffers */
-void osmo_e1_ts_reset(struct osmo_e1_instance_ts *e1t)
+void osmo_e1f_ts_reset(struct osmo_e1f_instance_ts *e1t)
 {
 	e1t->tx.underruns = 0;
 	msgb_queue_free(&e1t->tx.queue);
@@ -99,7 +99,7 @@
 
 /*! stop E1 instance; stops all timeslots and releases any pending rx/tx buffers
  *  \param[in] e1t E1 instance which we are to stop */
-void osmo_e1_instance_reset(struct osmo_e1_instance *e1i)
+void osmo_e1f_instance_reset(struct osmo_e1f_instance *e1i)
 {
 	int i;
 
@@ -119,8 +119,8 @@
 	e1i->rx.num_ts0_in_mframe_search = 0;
 
 	for (i = 1; i < ARRAY_SIZE(e1i->ts); i++) {
-		struct osmo_e1_instance_ts *e1t = &e1i->ts[i];
-		osmo_e1_ts_reset(e1t);
+		struct osmo_e1f_instance_ts *e1t = &e1i->ts[i];
+		osmo_e1f_ts_reset(e1t);
 	}
 }
 
@@ -128,7 +128,7 @@
  *  \param[in] e1i E1 intance on which we work
  *  \param[in] ts_nr E1 timeslot number (1..31)
  *  \returns pointer to timeslot; NULL on error */
-struct osmo_e1_instance_ts *osmo_e1_instance_ts(struct osmo_e1_instance *e1i, uint8_t ts_nr)
+struct osmo_e1f_instance_ts *osmo_e1f_instance_ts(struct osmo_e1f_instance *e1i, uint8_t ts_nr)
 {
 	if (ts_nr == 0 || ts_nr >= ARRAY_SIZE(e1i->ts))
 		return NULL;
@@ -142,8 +142,8 @@
  *  \param[in] enable enable (true) or disalble (false) receiving on this TS
  *  \param[in] mode the mode for this timeslot (raw or hdlc)
  *  \return 0 on success; negative on error */
-int osmo_e1_ts_config(struct osmo_e1_instance_ts *e1t, e1_data_cb cb, unsigned int granularity,
-		      bool enable, enum osmo_e1_ts_mode mode)
+int osmo_e1f_ts_config(struct osmo_e1f_instance_ts *e1t, e1_data_cb cb, unsigned int granularity,
+		      bool enable, enum osmo_e1f_ts_mode mode)
 {
 	e1t->rx.data_cb = cb;
 	e1t->rx.enabled = enable;
@@ -153,7 +153,7 @@
 	return 0;
 }
 
-const struct value_string osmo_e1_notifv_evt_names[] = {
+const struct value_string osmo_e1f_notifv_evt_names[] = {
 	{ E1_NTFY_EVT_ALIGN_FRAME, "Aligned to Frame" },
 	{ E1_NTFY_EVT_ALIGN_CRC_MFRAME, "Aligned to CRC4-Multiframe" },
 	{ E1_NTFY_EVT_CRC_ERROR, "CRC Error detected (local)" },
@@ -175,13 +175,13 @@
  *  Ownership of \a msg is transferred from caller into this function, but only
  *  in case of successful execution (return 0)!
  */
-void osmo_e1_ts_enqueue(struct osmo_e1_instance_ts *e1t, struct msgb *msg)
+void osmo_e1f_ts_enqueue(struct osmo_e1f_instance_ts *e1t, struct msgb *msg)
 {
 	msgb_enqueue(&e1t->tx.queue, msg);
 }
 
 /* obtain a CRC4 bit for the current frame number */
-static uint8_t e1_pull_crc4_bit(struct osmo_e1_instance *e1i)
+static uint8_t e1_pull_crc4_bit(struct osmo_e1f_instance *e1i)
 {
 	/* If CRC-4 is disabled, all CRC bits shall be '1' */
 	if (e1i->crc4_enabled == 0) {
@@ -204,7 +204,7 @@
 }
 
 /* pull a single to-be-transmitted byte for TS0 */
-static uint8_t e1_pull_ts0(struct osmo_e1_instance *e1i)
+static uint8_t e1_pull_ts0(struct osmo_e1f_instance *e1i)
 {
 	uint8_t ret;
 
@@ -249,7 +249,7 @@
 }
 
 /* pull a single to-be-transmitted byte for TS1..31 */
-static uint8_t e1_pull_tsN(struct osmo_e1_instance_ts *e1t)
+static uint8_t e1_pull_tsN(struct osmo_e1f_instance_ts *e1t)
 {
 	struct msgb *msg = llist_first_entry_or_null(&e1t->tx.queue, struct msgb, list);
 	uint8_t *cur;
@@ -271,7 +271,7 @@
 }
 
 /* update the current in-progress CRC4 value with data from \a out_frame */
-static void e1_tx_update_crc4(struct osmo_e1_instance *e1i, const uint8_t *out_frame)
+static void e1_tx_update_crc4(struct osmo_e1f_instance *e1i, const uint8_t *out_frame)
 {
 	uint8_t ts0;
 
@@ -288,7 +288,7 @@
  *  \param e1i E1 instance for which the frame shall be generated
  *  \param[out] out_frame callee-allocated buffer to which function stores 32 bytes
  *  \returns 0 on success, negative on error */
-int osmo_e1_pull_tx_frame(struct osmo_e1_instance *e1i, uint8_t *out_frame)
+int osmo_e1f_pull_tx_frame(struct osmo_e1f_instance *e1i, uint8_t *out_frame)
 {
 	int i;
 
@@ -297,7 +297,7 @@
 
 	/* generate TS1..31 */
 	for (i = 1; i < ARRAY_SIZE(e1i->ts); i++) {
-		struct osmo_e1_instance_ts *e1t = &e1i->ts[i];
+		struct osmo_e1f_instance_ts *e1t = &e1i->ts[i];
 		/* get next to-be-transmitted byte from the TS */
 		out_frame[i] = e1_pull_tsN(e1t);
 	}
@@ -336,13 +336,13 @@
 };
 
 /* get a TS0 byte from the history. delta 0 == current, delte 1 == previous, ... */
-static uint8_t get_ts0_hist(struct osmo_e1_instance *e1i, uint8_t delta)
+static uint8_t get_ts0_hist(struct osmo_e1f_instance *e1i, uint8_t delta)
 {
 	return e1i->rx.ts0_history[((e1i->rx.frame_nr + 16)-delta) % 16];
 }
 
 /* ITU-T G.706 Section 4.1.1 */
-static bool frame_alignment_lost(struct osmo_e1_instance *e1i)
+static bool frame_alignment_lost(struct osmo_e1f_instance *e1i)
 {
 	if (e1i->rx.frame_nr % 2)
 		return false;
@@ -358,7 +358,7 @@
 }
 
 /* ITU-T G.706 Section 4.1.2 */
-static bool frame_alignment_recovered(struct osmo_e1_instance *e1i)
+static bool frame_alignment_recovered(struct osmo_e1f_instance *e1i)
 {
 	/* two consecutive FAS with one non-FAS interspersed */
 	if (is_correct_fas(get_ts0_hist(e1i, 0)) &&
@@ -370,7 +370,7 @@
 }
 
 /* ITU-T G.706 Section 4.2 */
-static bool crc_mframe_alignment_achieved(struct osmo_e1_instance *e1i)
+static bool crc_mframe_alignment_achieved(struct osmo_e1f_instance *e1i)
 {
 	/* if current TS0 byte is FAS, we cannot detect alignment */
 	if (is_correct_fas(get_ts0_hist(e1i, 0)))
@@ -387,7 +387,7 @@
 }
 
 /* Get the CRC4 that was received from our Rx TS0 history */
-static uint8_t crc4_from_ts0_hist(struct osmo_e1_instance *e1i, bool smf2)
+static uint8_t crc4_from_ts0_hist(struct osmo_e1f_instance *e1i, bool smf2)
 {
 	uint8_t crc = 0;
 	uint8_t offset = 0;
@@ -404,7 +404,7 @@
 }
 
 /* update the current in-progress CRC4 value with data from \a rx_frame */
-static void e1_rx_update_crc4(struct osmo_e1_instance *e1i, const uint8_t *rx_frame)
+static void e1_rx_update_crc4(struct osmo_e1f_instance *e1i, const uint8_t *rx_frame)
 {
 	uint8_t ts0;
 
@@ -420,7 +420,7 @@
 /* FSM State handler */
 static void e1_align_search_frame(struct osmo_fsm_inst *fi, uint32_t event, void *data)
 {
-	struct osmo_e1_instance *e1i = (struct osmo_e1_instance *) fi->priv;
+	struct osmo_e1f_instance *e1i = (struct osmo_e1f_instance *) fi->priv;
 
 	if (frame_alignment_recovered(e1i)) {
 		/* if we detected the 2nd FAS, we must be in FN 2 (or at least FN%2=0 */
@@ -433,7 +433,7 @@
 /* FSM State handler */
 static void e1_align_search_crc_mframe(struct osmo_fsm_inst *fi, uint32_t event, void *data)
 {
-	struct osmo_e1_instance *e1i = (struct osmo_e1_instance *) fi->priv;
+	struct osmo_e1f_instance *e1i = (struct osmo_e1f_instance *) fi->priv;
 
 	if (crc_mframe_alignment_achieved(e1i)) {
 		/* if we detected the 6-bit CRC multiframe signal, we must be in FN 11 */
@@ -453,7 +453,7 @@
 	}
 }
 
-static void e1_aligned_common(struct osmo_e1_instance *e1i)
+static void e1_aligned_common(struct osmo_e1f_instance *e1i)
 {
 	uint8_t inb = get_ts0_hist(e1i, 0);
 
@@ -473,7 +473,7 @@
 /* FSM State handler */
 static void e1_aligned_crc_mframe(struct osmo_fsm_inst *fi, uint32_t event, void *data)
 {
-	struct osmo_e1_instance *e1i = (struct osmo_e1_instance *) fi->priv;
+	struct osmo_e1f_instance *e1i = (struct osmo_e1f_instance *) fi->priv;
 
 	if (frame_alignment_lost(e1i)) {
 		osmo_fsm_inst_state_chg(fi, E1_AS_SEARCH_FRAME, 0, 0);
@@ -526,7 +526,7 @@
 /* FSM State handler */
 static void e1_aligned_basic(struct osmo_fsm_inst *fi, uint32_t event, void *data)
 {
-	struct osmo_e1_instance *e1i = (struct osmo_e1_instance *) fi->priv;
+	struct osmo_e1f_instance *e1i = (struct osmo_e1f_instance *) fi->priv;
 
 	if (frame_alignment_lost(e1i)) {
 		osmo_fsm_inst_state_chg(fi, E1_AS_SEARCH_FRAME, 0, 0);
@@ -571,7 +571,7 @@
 
 static void e1_allstate(struct osmo_fsm_inst *fi, uint32_t event, void *data)
 {
-	struct osmo_e1_instance *e1i = (struct osmo_e1_instance *) fi->priv;
+	struct osmo_e1f_instance *e1i = (struct osmo_e1f_instance *) fi->priv;
 
 	switch (event) {
 	case E1_AE_RESET:
@@ -591,19 +591,19 @@
 	.event_names = e1_align_evt_names,
 };
 
-static void align_fsm_reset(struct osmo_e1_instance *e1i)
+static void align_fsm_reset(struct osmo_e1f_instance *e1i)
 {
 	osmo_fsm_inst_dispatch(e1i->rx.fi, E1_AE_RESET, NULL);
 }
 
-static void e1_rx_hist_add(struct osmo_e1_instance *e1i, uint8_t inb)
+static void e1_rx_hist_add(struct osmo_e1f_instance *e1i, uint8_t inb)
 {
 	e1i->rx.ts0_history[e1i->rx.frame_nr] = inb;
 	if (e1i->rx.ts0_hist_len < 16)
 		e1i->rx.ts0_hist_len++;
 }
 
-static void e1_rx_ts0(struct osmo_e1_instance *e1i, uint8_t inb)
+static void e1_rx_ts0(struct osmo_e1f_instance *e1i, uint8_t inb)
 {
 	/* append just-received byte to the TS0 receive history buffer */
 	e1_rx_hist_add(e1i, inb);
@@ -614,7 +614,7 @@
 	e1i->rx.frame_nr = (e1i->rx.frame_nr + 1) % 16;
 }
 
-static void e1_rx_tsN(struct osmo_e1_instance_ts *e1t, uint8_t inb)
+static void e1_rx_tsN(struct osmo_e1f_instance_ts *e1t, uint8_t inb)
 {
 	struct msgb *msg;
 	int count, rc;
@@ -628,7 +628,7 @@
 	OSMO_ASSERT(msg);
 
 	switch (e1t->mode) {
-	case OSMO_E1_TS_RAW:
+	case OSMO_E1F_TS_RAW:
 		/* append byte at end of msgb */
 		msgb_put_u8(msg, inb);
 		/* flush msgb, if full */
@@ -636,7 +636,7 @@
 			goto flush;
 		}
 		break;
-	case OSMO_E1_TS_HDLC_CRC:
+	case OSMO_E1F_TS_HDLC_CRC:
 		rc = osmo_isdnhdlc_decode(&e1t->rx.hdlc, &inb, 1, &count,
 					  msgb_data(msg), msgb_tailroom(msg));
 		switch (rc) {
@@ -677,7 +677,7 @@
  *  i.e. the first bit of TS0 of the frame will be octet-aligned and hence the
  *  entire 256bit buffer is provided as octet-aligned 32bytes in \a in_frame.
  */
-int osmo_e1_rx_frame(struct osmo_e1_instance *e1i, const uint8_t *in_frame)
+int osmo_e1f_rx_frame(struct osmo_e1f_instance *e1i, const uint8_t *in_frame)
 {
 	int i;
 
@@ -686,14 +686,14 @@
 	e1_rx_ts0(e1i, in_frame[0]);
 
 	for (i = 1; i < ARRAY_SIZE(e1i->ts); i++) {
-		struct osmo_e1_instance_ts *e1t = &e1i->ts[i];
+		struct osmo_e1f_instance_ts *e1t = &e1i->ts[i];
 		e1_rx_tsN(e1t, in_frame[i]);
 	}
 
 	return 0;
 }
 
-int osmo_e1_init(void)
+int osmo_e1f_init(void)
 {
 	return osmo_fsm_register(&e1_align_fsm);
 }
diff --git a/src/osmo_e1f.h b/src/osmo_e1f.h
new file mode 100644
index 0000000..c9d4778
--- /dev/null
+++ b/src/osmo_e1f.h
@@ -0,0 +1,122 @@
+#pragma once
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/core/fsm.h>
+#include <osmocom/core/isdnhdlc.h>
+
+struct osmo_e1f_tx_state {
+	bool remote_alarm;
+	bool crc4_error;
+	/* lower 5 bits: Sa4..Sa8 */
+	uint8_t sa4_sa8;
+	/* frame number 0..15 */
+	uint8_t frame_nr;
+	uint8_t crc4_last_smf;
+	uint8_t crc4;
+};
+
+struct osmo_e1f_rx_state {
+	uint8_t frame_nr;
+	/* history of rceived TS0 octets */
+	uint8_t ts0_history[16];
+	uint8_t ts0_hist_len;
+	/* was a remote alarm received? */
+	bool remote_alarm;
+	bool remote_crc4_error;
+	/* number of TS0 bytes received since entering CRC mframe search */
+	uint8_t num_ts0_in_mframe_search;
+	struct osmo_fsm_inst *fi;
+	/* computed CRC4 */
+	uint8_t crc4_last_smf;
+	uint8_t crc4;
+};
+
+enum osmo_e1f_notify_event {
+	E1_NTFY_EVT_ALIGN_FRAME,
+	E1_NTFY_EVT_ALIGN_CRC_MFRAME,
+	E1_NTFY_EVT_CRC_ERROR,
+	E1_NTFY_EVT_REMOTE_CRC_ERROR,
+	E1_NTFY_EVT_REMOTE_ALARM,
+};
+
+enum osmo_e1f_ts_mode {
+       OSMO_E1F_TS_RAW,
+       OSMO_E1F_TS_HDLC_CRC,
+};
+
+struct osmo_e1f_instance_ts;
+struct osmo_e1f_instance;
+typedef void (*e1_data_cb)(struct osmo_e1f_instance_ts *ts, struct msgb *msg);
+typedef void (*e1_notify_cb)(struct osmo_e1f_instance *e1i, enum osmo_e1f_notify_event evt,
+			     bool present, void *data);
+
+struct osmo_e1f_instance_ts {
+	/* timeslot number */
+	uint8_t ts_nr;
+	/* mode in which we operate (RAW/HDLC) */
+	enum osmo_e1f_ts_mode mode;
+	/* back-pointer to e1 instance */
+	struct osmo_e1f_instance *inst;
+	struct {
+		/* optional HDLC encoder state */
+		struct osmo_isdnhdlc_vars hdlc;
+		/* queue of pending to-be-transmitted messages */
+		struct llist_head queue;
+		unsigned long underruns;
+	} tx;
+	struct {
+		/* optional HDLC decoder state */
+		struct osmo_isdnhdlc_vars hdlc;
+		bool enabled;
+		/* how many bytes to buffer before calling call-back */
+		unsigned int granularity;
+		/* current receive buffer */
+		struct msgb *msg;
+		e1_data_cb data_cb;
+		/* private data, relevant to user */
+		void *priv;
+	} rx;
+};
+
+struct osmo_e1f_instance {
+	/* list; currently not used yet */
+	struct llist_head list;
+
+	/* is CRC4 generation + parsing enabled? */
+	bool crc4_enabled;
+	/* notification call-back function */
+	e1_notify_cb notify_cb;
+
+	/* Rx + Tx related state */
+	struct osmo_e1f_tx_state tx;
+	struct osmo_e1f_rx_state rx;
+
+	/* our 32 timeslots (only 1..32 are used) */
+	struct osmo_e1f_instance_ts ts[32];
+
+	/* private data, relevant to user */
+	void *priv;
+};
+
+extern const struct value_string osmo_e1f_notifv_evt_names[];
+
+static inline const char *osmo_e1f_notify_event_name(enum osmo_e1f_notify_event evt) {
+	return get_value_string(osmo_e1f_notifv_evt_names, evt);
+}
+
+int osmo_e1f_init(void);
+struct osmo_e1f_instance_ts *osmo_e1f_instance_ts(struct osmo_e1f_instance *e1i, uint8_t ts_nr);
+int osmo_e1f_instance_init(struct osmo_e1f_instance *e1i, const char *name, e1_notify_cb cb,
+			  bool crc4_enabled, void *priv);
+void osmo_e1f_instance_reset(struct osmo_e1f_instance *e1i);
+int osmo_e1f_ts_config(struct osmo_e1f_instance_ts *e1t, e1_data_cb cb, unsigned int granularity,
+		      bool enable, enum osmo_e1f_ts_mode mode);
+void osmo_e1f_ts_reset(struct osmo_e1f_instance_ts *e1t);
+
+
+void osmo_e1f_ts_enqueue(struct osmo_e1f_instance_ts *e1t, struct msgb *msg);
+int osmo_e1f_pull_tx_frame(struct osmo_e1f_instance *e1i, uint8_t *out_frame);
+int osmo_e1f_rx_frame(struct osmo_e1f_instance *e1i, const uint8_t *in_frame);