diff --git a/Makefile b/Makefile
index 4548cd6..8619ad7 100644
--- a/Makefile
+++ b/Makefile
@@ -123,6 +123,7 @@ OBJ=\
     drivers/device.o \
     drivers/bsl.o \
     drivers/fet.o \
+    drivers/fet_proto.o \
     drivers/fet_error.o \
     drivers/fet_db.o \
     drivers/flash_bsl.o \
diff --git a/drivers/fet.c b/drivers/fet.c
index 3145a0d..035ff11 100644
--- a/drivers/fet.c
+++ b/drivers/fet.c
@@ -1,5 +1,5 @@
 /* MSPDebug - debugging tool for the eZ430
- * Copyright (C) 2009, 2010 Daniel Beer
+ * Copyright (C) 2009-2012 Daniel Beer
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -30,6 +30,7 @@
 #include "util.h"
 #include "fet.h"
 #include "fet_error.h"
+#include "fet_proto.h"
 #include "fet_db.h"
 #include "output.h"
 #include "opdb.h"
@@ -42,45 +43,19 @@
 #include "cdc_acm.h"
 #include "obl.h"
 
-/* Send data in separate packets, as in the RF2500 */
-#define FET_PROTO_SEPARATE_DATA		0x01
-
-/* Received packets have an extra trailing byte */
-#define FET_PROTO_EXTRA_RECV		0x02
-
-/* Command packets have no leading \x7e */
-#define FET_PROTO_NOLEAD_SEND		0x04
-
 /* The new identify method should always be used */
-#define FET_PROTO_IDENTIFY_NEW		0x08
+#define FET_IDENTIFY_NEW		0x08
 
 /* A reset on startup should always be performed */
-#define FET_PROTO_FORCE_RESET           0x10
-
-#define MAX_PARAMS		16
-#define MAX_BLOCK_SIZE		4096
+#define FET_FORCE_RESET			0x10
 
 struct fet_device {
 	struct device                   base;
 
-	transport_t                     transport;
-	int				flags;
 	int                             version;
+	int				fet_flags;
 
-	uint8_t                         fet_buf[65538];
-	int                             fet_len;
-
-	/* Recieved packet is parsed into this struct */
-	struct {
-		int		command_code;
-		int		state;
-
-		int		argc;
-		uint32_t	argv[MAX_PARAMS];
-
-		uint8_t	*data;
-		int		datalen;
-	} fet_reply;
+	struct fet_proto		proto;
 };
 
 /**********************************************************************
@@ -156,344 +131,6 @@ struct fet_device {
 #define FET_POLL_RUNNING        0x01
 #define FET_POLL_BREAKPOINT     0x02
 
-/*********************************************************************
- * Checksum calculation
- *
- * This code table is also derived from uif430.
- */
-
-static const uint16_t fcstab[256] = {
-        0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
-        0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
-        0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
-        0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
-        0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
-        0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
-        0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
-        0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
-        0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
-        0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
-        0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
-        0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
-        0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
-        0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
-        0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
-        0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
-        0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
-        0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
-        0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
-        0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
-        0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
-        0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
-        0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
-        0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
-        0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
-        0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
-        0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
-        0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
-        0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
-        0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
-        0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
-        0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
-};
-
-static uint16_t calc_checksum(uint8_t *cp, int len)
-{
-	uint16_t fcs = 0xffff;
-
-        while (len--) {
-                fcs = (fcs >> 8) ^ fcstab[(fcs ^ *cp++) & 0xff];
-        }
-
-        return fcs ^ 0xffff;
-}
-
-/*********************************************************************
- * FET packet transfer. This level of the interface deals in packets
- * send to/from the device.
- */
-
-/* This is a type of data transfer which appears to be unique to
- * the RF2500. Blocks of data are sent to an internal buffer. Each
- * block is prefixed with a buffer offset and a payload length.
- *
- * No checksums are included.
- */
-static int send_rf2500_data(struct fet_device *dev,
-			    const uint8_t *data, int len)
-{
-	int offset = 0;
-
-	while (len) {
-		uint8_t pbuf[63];
-		int plen = len > 59 ? 59 : len;
-
-		pbuf[0] = 0x83;
-		pbuf[1] = offset & 0xff;
-		pbuf[2] = offset >> 8;
-		pbuf[3] = plen;
-		memcpy(pbuf + 4, data, plen);
-		if (dev->transport->ops->send(dev->transport,
-			pbuf, plen + 4) < 0)
-			return -1;
-
-		data += plen;
-		len -= plen;
-		offset += plen;
-	}
-
-	return 0;
-}
-
-#define PTYPE_ACK		0
-#define PTYPE_CMD		1
-#define PTYPE_PARAM		2
-#define PTYPE_DATA		3
-#define PTYPE_MIXED		4
-#define PTYPE_NAK		5
-#define PTYPE_FLASH_ACK		6
-
-static int parse_packet(struct fet_device *dev, int plen)
-{
-	uint16_t c = calc_checksum(dev->fet_buf + 2, plen - 2);
-	uint16_t r = LE_WORD(dev->fet_buf, plen);
-	int i = 2;
-	int type;
-	int error;
-
-	if (c != r) {
-		printc_err("fet: checksum error (calc %04x,"
-			" recv %04x)\n", c, r);
-		return -1;
-	}
-
-	if (plen < 6)
-		goto too_short;
-
-	dev->fet_reply.command_code = dev->fet_buf[i++];
-	type = dev->fet_buf[i++];
-	dev->fet_reply.state = dev->fet_buf[i++];
-	error = dev->fet_buf[i++];
-
-	if (error) {
-		printc_err("fet: FET returned error code %d (%s)\n",
-			error, fet_error(error));
-		return -1;
-	}
-
-	if (type == PTYPE_NAK) {
-		printc_err("fet: FET returned NAK\n");
-		return -1;
-	}
-
-	/* Parse packet parameters */
-	if (type == PTYPE_PARAM || type == PTYPE_MIXED) {
-		int j;
-
-		if (i + 2 > plen)
-			goto too_short;
-
-		dev->fet_reply.argc = LE_WORD(dev->fet_buf, i);
-		i += 2;
-
-		if (dev->fet_reply.argc >= MAX_PARAMS) {
-			printc_err("fet: too many params: %d\n",
-				dev->fet_reply.argc);
-			return -1;
-		}
-
-		for (j = 0; j < dev->fet_reply.argc; j++) {
-			if (i + 4 > plen)
-				goto too_short;
-			dev->fet_reply.argv[j] = LE_LONG(dev->fet_buf, i);
-			i += 4;
-		}
-	} else {
-		dev->fet_reply.argc = 0;
-	}
-
-	/* Extract a pointer to the data */
-	if (type == PTYPE_DATA || type == PTYPE_MIXED) {
-		if (i + 4 > plen)
-			goto too_short;
-
-		dev->fet_reply.datalen = LE_LONG(dev->fet_buf, i);
-		i += 4;
-
-		if (i + dev->fet_reply.datalen > plen)
-			goto too_short;
-
-		dev->fet_reply.data = dev->fet_buf + i;
-	} else {
-		dev->fet_reply.data = NULL;
-		dev->fet_reply.datalen = 0;
-	}
-
-	return 0;
-
-too_short:
-	printc_err("fet: too short (%d bytes)\n",
-		plen);
-	return -1;
-}
-
-/* Receive a packet from the FET. The usual format is:
- *     <length (2 bytes)> <data> <checksum>
- *
- * The length is that of the data + checksum. Olimex JTAG adapters follow
- * all packets with a trailing 0x7e byte, which must be discarded.
- */
-static int recv_packet(struct fet_device *dev)
-{
-	int pkt_extra = (dev->flags & FET_PROTO_EXTRA_RECV) ? 3 : 2;
-	int plen = LE_WORD(dev->fet_buf, 0);
-
-	/* If there's a packet still here from last time, get rid of it */
-	if (dev->fet_len >= plen + pkt_extra) {
-		memmove(dev->fet_buf, dev->fet_buf + plen + pkt_extra,
-			dev->fet_len - plen - pkt_extra);
-		dev->fet_len -= plen + pkt_extra;
-	}
-
-	/* Keep adding data to the buffer until we have a complete packet */
-	for (;;) {
-		int len;
-
-		plen = LE_WORD(dev->fet_buf, 0);
-		if (dev->fet_len >= plen + pkt_extra)
-			return parse_packet(dev, plen);
-
-		len = dev->transport->ops->recv(dev->transport,
-						dev->fet_buf + dev->fet_len,
-						sizeof(dev->fet_buf) -
-						dev->fet_len);
-		if (len < 0)
-			return -1;
-		dev->fet_len += len;
-	}
-
-	return -1;
-}
-
-static int send_command(struct fet_device *dev, int command_code,
-		        const uint32_t *params, int nparams,
-			const uint8_t *extra, int exlen)
-{
-	uint8_t datapkt[MAX_BLOCK_SIZE * 2];
-	int len = 0;
-
-	uint8_t buf[MAX_BLOCK_SIZE * 3];
-	uint16_t cksum;
-	int i = 0;
-	int j;
-
-	assert (len + exlen + 2 <= sizeof(datapkt));
-
-	/* Command code and packet type */
-	datapkt[len++] = command_code;
-	datapkt[len++] = ((nparams > 0) ? 1 : 0) + ((exlen > 0) ? 2 : 0) + 1;
-
-	/* Optional parameters */
-	if (nparams > 0) {
-		datapkt[len++] = nparams & 0xff;
-		datapkt[len++] = nparams >> 8;
-
-		for (j = 0; j < nparams; j++) {
-			uint32_t p = params[j];
-
-			datapkt[len++] = p & 0xff;
-			p >>= 8;
-			datapkt[len++] = p & 0xff;
-			p >>= 8;
-			datapkt[len++] = p & 0xff;
-			p >>= 8;
-			datapkt[len++] = p & 0xff;
-		}
-	}
-
-	/* Extra data */
-	if (extra) {
-		int x = exlen;
-
-		datapkt[len++] = x & 0xff;
-		x >>= 8;
-		datapkt[len++] = x & 0xff;
-		x >>= 8;
-		datapkt[len++] = x & 0xff;
-		x >>= 8;
-		datapkt[len++] = x & 0xff;
-
-		memcpy(datapkt + len, extra, exlen);
-		len += exlen;
-	}
-
-	/* Checksum */
-	cksum = calc_checksum(datapkt, len);
-	datapkt[len++] = cksum & 0xff;
-	datapkt[len++] = cksum >> 8;
-
-	/* Copy into buf, escaping special characters and adding
-	 * delimeters.
-	 */
-	if (!(dev->flags & FET_PROTO_NOLEAD_SEND))
-		buf[i++] = 0x7e;
-
-	for (j = 0; j < len; j++) {
-		char c = datapkt[j];
-
-		if (c == 0x7e || c == 0x7d) {
-			buf[i++] = 0x7d;
-			c ^= 0x20;
-		}
-
-		buf[i++] = c;
-	}
-	buf[i++] = 0x7e;
-
-	assert (i < sizeof(buf));
-
-	return dev->transport->ops->send(dev->transport, buf, i);
-}
-
-static int xfer(struct fet_device *dev,
-		int command_code, const uint8_t *data, int datalen,
-		int nparams, ...)
-{
-	uint32_t params[MAX_PARAMS];
-	int i;
-	va_list ap;
-
-	assert (nparams <= MAX_PARAMS);
-
-	va_start(ap, nparams);
-	for (i = 0; i < nparams; i++)
-		params[i] = va_arg(ap, uint32_t);
-	va_end(ap);
-
-	if (data && (dev->flags & FET_PROTO_SEPARATE_DATA)) {
-		assert (nparams + 1 <= MAX_PARAMS);
-		params[nparams++] = datalen;
-
-		if (send_rf2500_data(dev, data, datalen) < 0)
-			return -1;
-		if (send_command(dev, command_code, params, nparams,
-				 NULL, 0) < 0)
-			return -1;
-	} else if (send_command(dev, command_code, params, nparams,
-				data, datalen) < 0)
-		return -1;
-
-	if (recv_packet(dev) < 0)
-		return -1;
-
-	if (dev->fet_reply.command_code != command_code) {
-		printc_err("fet: reply type mismatch\n");
-		return -1;
-	}
-
-	return 0;
-}
-
 /**********************************************************************
  * MSP430 high-level control functions
  */
@@ -508,18 +145,18 @@ static int identify_old(struct fet_device *dev)
 {
 	char idtext[64];
 
-	if (xfer(dev, C_IDENTIFY, NULL, 0, 2, 70, 0) < 0)
+	if (fet_proto_xfer(&dev->proto, C_IDENTIFY, NULL, 0, 2, 70, 0) < 0)
 		return -1;
 
-	if (dev->fet_reply.datalen < 0x26) {
+	if (dev->proto.datalen < 0x26) {
 		printc_err("fet: missing info\n");
 		return -1;
 	}
 
-	memcpy(idtext, dev->fet_reply.data + 4, 32);
+	memcpy(idtext, dev->proto.data + 4, 32);
 	idtext[32] = 0;
 
-	dev->base.max_breakpoints = LE_WORD(dev->fet_reply.data, 0x2a);
+	dev->base.max_breakpoints = LE_WORD(dev->proto.data, 0x2a);
 
 	show_dev_info(idtext, dev);
 
@@ -530,29 +167,29 @@ static int identify_new(struct fet_device *dev, const char *force_id)
 {
 	const struct fet_db_record *r;
 
-	if (xfer(dev, C_IDENT1, NULL, 0, 2, 0, 0) < 0) {
+	if (fet_proto_xfer(&dev->proto, C_IDENT1, NULL, 0, 2, 0, 0) < 0) {
 		printc_err("fet: command C_IDENT1 failed\n");
 		return -1;
 	}
 
-	if (dev->fet_reply.datalen < 2) {
+	if (dev->proto.datalen < 2) {
 		printc_err("fet: missing info\n");
 		return -1;
 	}
 
 	printc_dbg("Device ID: 0x%02x%02x\n",
-	       dev->fet_reply.data[0], dev->fet_reply.data[1]);
+	       dev->proto.data[0], dev->proto.data[1]);
 
 	if (force_id)
 		r = fet_db_find_by_name(force_id);
 	else
-		r = fet_db_find_by_msg28(dev->fet_reply.data,
-					 dev->fet_reply.datalen);
+		r = fet_db_find_by_msg28(dev->proto.data,
+					 dev->proto.datalen);
 
 	if (!r) {
 		printc_err("fet: unknown device\n");
-		debug_hexdump("msg28_data:", dev->fet_reply.data,
-			      dev->fet_reply.datalen);
+		debug_hexdump("msg28_data:", dev->proto.data,
+			      dev->proto.datalen);
 		return -1;
 	}
 
@@ -590,12 +227,14 @@ static int identify_new(struct fet_device *dev, const char *force_id)
 
 	show_dev_info(r->name, dev);
 
-	if (xfer(dev, C_IDENT3, r->msg2b_data, r->msg2b_len, 0) < 0)
+	if (fet_proto_xfer(&dev->proto, C_IDENT3,
+			   r->msg2b_data, r->msg2b_len, 0) < 0)
 		printc_err("fet: warning: message C_IDENT3 failed\n");
 
-	if (xfer(dev, C_IDENT2, r->msg29_data, FET_DB_MSG29_LEN,
-		 3, r->msg29_params[0], r->msg29_params[1],
-		 r->msg29_params[2]) < 0) {
+	if (fet_proto_xfer(&dev->proto, C_IDENT2,
+			   r->msg29_data, FET_DB_MSG29_LEN,
+			   3, r->msg29_params[0], r->msg29_params[1],
+			   r->msg29_params[2]) < 0) {
 		printc_err("fet: message C_IDENT2 failed\n");
 		return -1;
 	}
@@ -605,7 +244,7 @@ static int identify_new(struct fet_device *dev, const char *force_id)
 
 static int do_identify(struct fet_device *dev, const char *force_id)
 {
-	if (dev->flags & FET_PROTO_IDENTIFY_NEW)
+	if (dev->fet_flags & FET_IDENTIFY_NEW)
 		return identify_new(dev, force_id);
 
 	if (dev->version < 20300000)
@@ -616,7 +255,7 @@ static int do_identify(struct fet_device *dev, const char *force_id)
 
 static int do_run(struct fet_device *dev, int type)
 {
-	if (xfer(dev, C_RUN, NULL, 0, 2, type, 0) < 0) {
+	if (fet_proto_xfer(&dev->proto, C_RUN, NULL, 0, 2, type, 0) < 0) {
 		printc_err("fet: failed to restart CPU\n");
 		return -1;
 	}
@@ -630,12 +269,16 @@ static int fet_erase(device_t dev_base, device_erase_type_t type,
 	struct fet_device *dev = (struct fet_device *)dev_base;
 	int fet_erase_type = FET_ERASE_MAIN;
 
-	if (xfer(dev, C_CONFIGURE, NULL, 0, 2, FET_CONFIG_CLKCTRL, 0x26) < 0) {
+	if (fet_proto_xfer(&dev->proto,
+			   C_CONFIGURE, NULL, 0,
+			   2, FET_CONFIG_CLKCTRL, 0x26) < 0) {
 		printc_err("fet: config (1) failed\n");
 		return -1;
 	}
 
-	if (xfer(dev, C_CONFIGURE, NULL, 0, 2, FET_CONFIG_FLASH_LOCK, 0) < 0) {
+	if (fet_proto_xfer(&dev->proto,
+			   C_CONFIGURE, NULL, 0,
+			   2, FET_CONFIG_FLASH_LOCK, 0) < 0) {
 		printc_err("fet: config (2) failed\n");
 		return -1;
 	}
@@ -660,7 +303,8 @@ static int fet_erase(device_t dev_base, device_erase_type_t type,
 		return -1;
 	}
 
-	if (xfer(dev, C_ERASE, NULL, 0, 3, fet_erase_type, addr, 0) < 0) {
+	if (fet_proto_xfer(&dev->proto, C_ERASE, NULL, 0,
+			   3, fet_erase_type, addr, 0) < 0) {
 		printc_err("fet: erase command failed\n");
 		return -1;
 	}
@@ -676,12 +320,12 @@ static device_status_t fet_poll(device_t dev_base)
 	if ((delay_ms(50) < 0) || ctrlc_check())
 		return DEVICE_STATUS_INTR;
 
-	if (xfer(dev, C_STATE, NULL, 0, 1, 0) < 0) {
+	if (fet_proto_xfer(&dev->proto, C_STATE, NULL, 0, 1, 0) < 0) {
 		printc_err("fet: polling failed\n");
 		return DEVICE_STATUS_ERROR;
 	}
 
-	if (!(dev->fet_reply.argv[0] & FET_POLL_RUNNING))
+	if (!(dev->proto.argv[0] & FET_POLL_RUNNING))
 		return DEVICE_STATUS_HALTED;
 
 	return DEVICE_STATUS_RUNNING;
@@ -702,8 +346,8 @@ static int refresh_bps(struct fet_device *dev)
 			if (!(bp->flags & DEVICE_BP_ENABLED))
 				addr = 0;
 
-			if (xfer(dev, C_BREAKPOINT, NULL, 0,
-				 2, i, addr) < 0) {
+			if (fet_proto_xfer(&dev->proto, C_BREAKPOINT, NULL, 0,
+					   2, i, addr) < 0) {
 				printc_err("fet: failed to refresh "
 					"breakpoint #%d\n", i);
 				ret = -1;
@@ -722,7 +366,8 @@ static int fet_ctl(device_t dev_base, device_ctl_t action)
 
 	switch (action) {
 	case DEVICE_CTL_RESET:
-		if (xfer(dev, C_RESET, NULL, 0, 3, FET_RESET_ALL, 0, 0) < 0) {
+		if (fet_proto_xfer(&dev->proto, C_RESET, NULL, 0,
+				   3, FET_RESET_ALL, 0, 0) < 0) {
 			printc_err("fet: reset failed\n");
 			return -1;
 		}
@@ -735,7 +380,7 @@ static int fet_ctl(device_t dev_base, device_ctl_t action)
 		return do_run(dev, FET_RUN_BREAKPOINT);
 
 	case DEVICE_CTL_HALT:
-		if (xfer(dev, C_STATE, NULL, 0, 1, 1) < 0) {
+		if (fet_proto_xfer(&dev->proto, C_STATE, NULL, 0, 1, 1) < 0) {
 			printc_err("fet: failed to halt CPU\n");
 			return -1;
 		}
@@ -772,14 +417,14 @@ static void fet_destroy(device_t dev_base)
 	 * FR5739, or else the value of the reset vector gets set to
 	 * 0xffff at the start of the next JTAG session.
 	 */
-	if (xfer(dev, C_RESET, NULL, 0, 3, FET_RESET_ALL, 1,
-		 !device_is_fram(dev_base)) < 0)
+	if (fet_proto_xfer(&dev->proto, C_RESET, NULL, 0, 3, FET_RESET_ALL, 1,
+			   !device_is_fram(dev_base)) < 0)
 		printc_err("fet: final reset failed\n");
 
-	if (xfer(dev, C_CLOSE, NULL, 0, 1, 0) < 0)
+	if (fet_proto_xfer(&dev->proto, C_CLOSE, NULL, 0, 1, 0) < 0)
 		printc_err("fet: close command failed\n");
 
-	dev->transport->ops->destroy(dev->transport);
+	dev->proto.transport->ops->destroy(dev->proto.transport);
 	free(dev);
 }
 
@@ -787,12 +432,13 @@ static int read_byte(struct fet_device *dev, address_t addr, uint8_t *out)
 {
 	address_t base = addr & ~1;
 
-	if (xfer(dev, C_READMEMORY, NULL, 0, 2, base, 2) < 0) {
+	if (fet_proto_xfer(&dev->proto, C_READMEMORY, NULL, 0,
+			   2, base, 2) < 0) {
 		printc_err("fet: failed to read byte from 0x%04x\n", addr);
 		return -1;
 	}
 
-	*out = dev->fet_reply.data[addr & 1];
+	*out = dev->proto.data[addr & 1];
 	return 0;
 }
 
@@ -801,16 +447,16 @@ static int write_byte(struct fet_device *dev, address_t addr, uint8_t value)
 	uint8_t buf[2];
 	address_t base = addr & ~1;
 
-	if (xfer(dev, C_READMEMORY, NULL, 0, 2, base, 2) < 0) {
+	if (fet_proto_xfer(&dev->proto, C_READMEMORY, NULL, 0, 2, base, 2) < 0) {
 		printc_err("fet: failed to read byte from 0x%04x\n", addr);
 		return -1;
 	}
 
-	buf[0] = dev->fet_reply.data[0];
-	buf[1] = dev->fet_reply.data[1];
+	buf[0] = dev->proto.data[0];
+	buf[1] = dev->proto.data[1];
 	buf[addr & 1] = value;
 
-	if (xfer(dev, C_WRITEMEMORY, buf, 2, 1, base) < 0) {
+	if (fet_proto_xfer(&dev->proto, C_WRITEMEMORY, buf, 2, 1, base) < 0) {
 		printc_err("fet: failed to write byte from 0x%04x\n", addr);
 		return -1;
 	}
@@ -824,8 +470,8 @@ static int get_adjusted_block_size(void)
 
 	if (block_size < 2)
 		block_size = 2;
-	if (block_size > MAX_BLOCK_SIZE)
-		block_size = MAX_BLOCK_SIZE;
+	if (block_size > FET_PROTO_MAX_BLOCK)
+		block_size = FET_PROTO_MAX_BLOCK;
 
 	return block_size;
 }
@@ -849,19 +495,20 @@ int fet_readmem(device_t dev_base, address_t addr, uint8_t *buffer,
 
 		plen &= ~0x1;
 
-		if (xfer(dev, C_READMEMORY, NULL, 0, 2, addr, plen) < 0) {
+		if (fet_proto_xfer(&dev->proto, C_READMEMORY, NULL, 0,
+				   2, addr, plen) < 0) {
 			printc_err("fet: failed to read "
 				"from 0x%04x\n", addr);
 			return -1;
 		}
 
-		if (dev->fet_reply.datalen < plen) {
+		if (dev->proto.datalen < plen) {
 			printc_err("fet: short data: "
-				"%d bytes\n", dev->fet_reply.datalen);
+				"%d bytes\n", dev->proto.datalen);
 			return -1;
 		}
 
-		memcpy(buffer, dev->fet_reply.data, plen);
+		memcpy(buffer, dev->proto.data, plen);
 		buffer += plen;
 		count -= plen;
 		addr += plen;
@@ -893,7 +540,8 @@ int fet_writemem(device_t dev_base, address_t addr,
 
 		plen &= ~0x1;
 
-		ret = xfer(dev, C_WRITEMEMORY, buffer, plen, 1, addr);
+		ret = fet_proto_xfer(&dev->proto,
+				     C_WRITEMEMORY, buffer, plen, 1, addr);
 
 		if (ret < 0) {
 			printc_err("fet: failed to write to 0x%04x\n",
@@ -917,17 +565,17 @@ static int fet_getregs(device_t dev_base, address_t *regs)
 	struct fet_device *dev = (struct fet_device *)dev_base;
 	int i;
 
-	if (xfer(dev, C_READREGISTERS, NULL, 0, 0) < 0)
+	if (fet_proto_xfer(&dev->proto, C_READREGISTERS, NULL, 0, 0) < 0)
 		return -1;
 
-	if (dev->fet_reply.datalen < DEVICE_NUM_REGS * 4) {
+	if (dev->proto.datalen < DEVICE_NUM_REGS * 4) {
 		printc_err("fet: short reply (%d bytes)\n",
-			dev->fet_reply.datalen);
+			dev->proto.datalen);
 		return -1;
 	}
 
 	for (i = 0; i < DEVICE_NUM_REGS; i++)
-		regs[i] = LE_LONG(dev->fet_reply.data, i * 4);
+		regs[i] = LE_LONG(dev->proto.data, i * 4);
 
 	return 0;
 }
@@ -948,7 +596,8 @@ static int fet_setregs(device_t dev_base, const address_t *regs)
 		buf[i * 4 + 3] = regs[i] >> 24;
 	}
 
-	ret = xfer(dev, C_WRITEREGISTERS, buf, sizeof(buf), 1, 0xffff);
+	ret = fet_proto_xfer(&dev->proto, C_WRITEREGISTERS,
+			     buf, sizeof(buf), 1, 0xffff);
 
 	if (ret < 0) {
 		printc_err("fet: context set failed\n");
@@ -959,11 +608,11 @@ static int fet_setregs(device_t dev_base, const address_t *regs)
 }
 
 static int do_configure(struct fet_device *dev,
-		        const struct device_args *args)
+			const struct device_args *args)
 {
 	if (!(args->flags & DEVICE_FLAG_JTAG)) {
-		if (!xfer(dev, C_CONFIGURE, NULL, 0,
-			  2, FET_CONFIG_PROTOCOL, 1)) {
+		if (!fet_proto_xfer(&dev->proto, C_CONFIGURE, NULL, 0,
+				    2, FET_CONFIG_PROTOCOL, 1)) {
 			printc_dbg("Configured for Spy-Bi-Wire\n");
 			return 0;
 		}
@@ -972,8 +621,8 @@ static int do_configure(struct fet_device *dev,
 		return -1;
 	}
 
-	if (!xfer(dev, C_CONFIGURE, NULL, 0,
-		  2, FET_CONFIG_PROTOCOL, 2)) {
+	if (!fet_proto_xfer(&dev->proto, C_CONFIGURE, NULL, 0,
+			    2, FET_CONFIG_PROTOCOL, 2)) {
 		printc_dbg("Configured for JTAG (2)\n");
 		return 0;
 	}
@@ -981,8 +630,8 @@ static int do_configure(struct fet_device *dev,
 	printc_err("fet: warning: JTAG configuration failed -- "
 		"retrying\n");
 
-	if (!xfer(dev, C_CONFIGURE, NULL, 0,
-		  2, FET_CONFIG_PROTOCOL, 0)) {
+	if (!fet_proto_xfer(&dev->proto, C_CONFIGURE, NULL, 0,
+			    2, FET_CONFIG_PROTOCOL, 0)) {
 		printc_dbg("Configured for JTAG (0)\n");
 		return 0;
 	}
@@ -994,28 +643,26 @@ static int do_configure(struct fet_device *dev,
 int try_open(struct fet_device *dev, const struct device_args *args,
 	     int send_reset)
 {
-	transport_t transport = dev->transport;
+	transport_t transport = dev->proto.transport;
 
-	if (dev->flags & FET_PROTO_NOLEAD_SEND) {
+	if (dev->proto.proto_flags & FET_PROTO_NOLEAD_SEND) {
 		printc("Resetting Olimex command processor...\n");
-		transport->ops->send(dev->transport,
-			(const uint8_t *)"\x7e", 1);
+		transport->ops->send(transport, (const uint8_t *)"\x7e", 1);
 		delay_ms(5);
-		transport->ops->send(dev->transport,
-			(const uint8_t *)"\x7e", 1);
+		transport->ops->send(transport, (const uint8_t *)"\x7e", 1);
 		delay_ms(5);
 	}
 
 	printc_dbg("Initializing FET...\n");
-	if (xfer(dev, C_INITIALIZE, NULL, 0, 0) < 0) {
+	if (fet_proto_xfer(&dev->proto, C_INITIALIZE, NULL, 0, 0) < 0) {
 		printc_err("fet: open failed\n");
 		return -1;
 	}
 
-	dev->version = dev->fet_reply.argv[0];
+	dev->version = dev->proto.argv[0];
 	printc_dbg("FET protocol version is %d\n", dev->version);
 
-	if (xfer(dev, 0x27, NULL, 0, 1, 4) < 0) {
+	if (fet_proto_xfer(&dev->proto, 0x27, NULL, 0, 1, 4) < 0) {
 		printc_err("fet: init failed\n");
 		return -1;
 	}
@@ -1025,12 +672,14 @@ int try_open(struct fet_device *dev, const struct device_args *args,
 
 	if (send_reset || args->flags & DEVICE_FLAG_FORCE_RESET) {
 		printc_dbg("Sending reset...\n");
-		if (xfer(dev, C_RESET, NULL, 0, 3, FET_RESET_ALL, 0, 0) < 0)
+		if (fet_proto_xfer(&dev->proto, C_RESET, NULL, 0,
+				   3, FET_RESET_ALL, 0, 0) < 0)
 			printc_err("warning: fet: reset failed\n");
 	}
 
 	/* set VCC */
-	if (xfer(dev, C_VCC, NULL, 0, 1, args->vcc_mv) < 0)
+	if (fet_proto_xfer(&dev->proto, C_VCC, NULL, 0,
+			   1, args->vcc_mv) < 0)
 		printc_err("warning: fet: set VCC failed\n");
 	else
 		printc_dbg("Set Vcc: %d mV\n", args->vcc_mv);
@@ -1045,8 +694,9 @@ int try_open(struct fet_device *dev, const struct device_args *args,
 }
 
 static device_t fet_open(const struct device_args *args,
-		         int flags, transport_t transport,
-		         const struct device_class *type)
+			 int proto_flags, transport_t transport,
+			 int fet_flags,
+			 const struct device_class *type)
 {
 	struct fet_device *dev = malloc(sizeof(*dev));
 	int i;
@@ -1058,11 +708,12 @@ static device_t fet_open(const struct device_args *args,
 
 	memset(dev, 0, sizeof(*dev));
 
-	dev->base.type = type;
-	dev->transport = transport;
-	dev->flags = flags;
+	fet_proto_init(&dev->proto, transport, proto_flags);
 
-	if (try_open(dev, args, flags & FET_PROTO_FORCE_RESET) < 0) {
+	dev->base.type = type;
+	dev->fet_flags = fet_flags;
+
+	if (try_open(dev, args, fet_flags & FET_FORCE_RESET) < 0) {
 		delay_ms(500);
 		printc("Trying again...\n");
 		if (try_open(dev, args, 1) < 0)
@@ -1092,11 +743,12 @@ static device_t fet_open_rf2500(const struct device_args *args)
 		return NULL;
 	}
 
-        trans = rf2500_open(args->path, args->requested_serial);
-        if (!trans)
-                return NULL;
+	trans = rf2500_open(args->path, args->requested_serial);
+	if (!trans)
+		return NULL;
 
-        return fet_open(args, FET_PROTO_SEPARATE_DATA, trans, &device_rf2500);
+	return fet_open(args, FET_PROTO_SEPARATE_DATA, trans,
+			0, &device_rf2500);
 }
 
 const struct device_class device_rf2500 = {
@@ -1156,9 +808,11 @@ static device_t fet_open_olimex_iso_mk2(const struct device_args *args)
 	if (!obl_get_version(trans, &version))
 		printc_dbg("Olimex firmware version: %x\n", version);
 
-	return fet_open(args, FET_PROTO_NOLEAD_SEND | FET_PROTO_EXTRA_RECV |
-			      FET_PROTO_IDENTIFY_NEW | FET_PROTO_FORCE_RESET,
-			trans, &device_olimex_iso_mk2);
+	return fet_open(args,
+			FET_PROTO_NOLEAD_SEND | FET_PROTO_EXTRA_RECV,
+			trans,
+			FET_FORCE_RESET | FET_IDENTIFY_NEW,
+			&device_olimex_iso_mk2);
 }
 
 const struct device_class device_olimex_iso_mk2 = {
@@ -1189,9 +843,11 @@ static device_t fet_open_olimex(const struct device_args *args)
 	if (!trans)
 		return NULL;
 
-	return fet_open(args, FET_PROTO_NOLEAD_SEND | FET_PROTO_EXTRA_RECV |
-			      FET_PROTO_IDENTIFY_NEW | FET_PROTO_FORCE_RESET,
-			trans, &device_olimex);
+	return fet_open(args,
+			FET_PROTO_NOLEAD_SEND | FET_PROTO_EXTRA_RECV,
+			trans,
+			FET_IDENTIFY_NEW | FET_FORCE_RESET,
+			&device_olimex);
 }
 
 const struct device_class device_olimex = {
@@ -1222,9 +878,11 @@ static device_t fet_open_olimex_v1(const struct device_args *args)
         if (!trans)
                 return NULL;
 
-	return fet_open(args, FET_PROTO_NOLEAD_SEND | FET_PROTO_EXTRA_RECV |
-			      FET_PROTO_IDENTIFY_NEW,
-			trans, &device_olimex_v1);
+	return fet_open(args,
+			FET_PROTO_NOLEAD_SEND | FET_PROTO_EXTRA_RECV,
+			trans,
+			FET_IDENTIFY_NEW,
+			&device_olimex_v1);
 }
 
 const struct device_class device_olimex_v1 = {
@@ -1255,9 +913,11 @@ static device_t fet_open_olimex_iso(const struct device_args *args)
 	if (!trans)
 		return NULL;
 
-	return fet_open(args, FET_PROTO_NOLEAD_SEND | FET_PROTO_EXTRA_RECV |
-			      FET_PROTO_IDENTIFY_NEW,
-			trans, &device_olimex_iso);
+	return fet_open(args,
+			FET_PROTO_NOLEAD_SEND | FET_PROTO_EXTRA_RECV,
+			trans,
+			FET_IDENTIFY_NEW,
+			&device_olimex_iso);
 }
 
 const struct device_class device_olimex_iso = {
@@ -1287,7 +947,7 @@ static device_t fet_open_uif(const struct device_args *args)
 	if (!trans)
 		return NULL;
 
-	return fet_open(args, 0, trans, &device_uif);
+	return fet_open(args, 0, trans, 0, &device_uif);
 }
 
 const struct device_class device_uif = {
diff --git a/drivers/fet_proto.c b/drivers/fet_proto.c
new file mode 100644
index 0000000..540ac78
--- /dev/null
+++ b/drivers/fet_proto.c
@@ -0,0 +1,371 @@
+/* MSPDebug - debugging tool for the eZ430
+ * Copyright (C) 2009-2012 Daniel Beer
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#include <stdarg.h>
+#include <assert.h>
+#include <string.h>
+
+#include "util.h"
+#include "fet_proto.h"
+#include "fet_error.h"
+#include "output.h"
+
+/*********************************************************************
+ * Checksum calculation
+ *
+ * This code table is also derived from uif430.
+ */
+
+static const uint16_t fcstab[256] = {
+	0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
+	0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
+	0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
+	0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
+	0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
+	0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
+	0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
+	0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
+	0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
+	0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
+	0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
+	0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
+	0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
+	0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
+	0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
+	0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
+	0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
+	0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
+	0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
+	0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
+	0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
+	0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
+	0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
+	0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
+	0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
+	0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
+	0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
+	0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
+	0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
+	0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
+	0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
+	0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
+};
+
+static uint16_t calc_checksum(uint8_t *cp, int len)
+{
+	uint16_t fcs = 0xffff;
+
+	while (len--) {
+		fcs = (fcs >> 8) ^ fcstab[(fcs ^ *cp++) & 0xff];
+	}
+
+	return fcs ^ 0xffff;
+}
+
+/*********************************************************************
+ * FET packet transfer. This level of the interface deals in packets
+ * send to/from the device.
+ */
+
+/* This is a type of data transfer which appears to be unique to
+ * the RF2500. Blocks of data are sent to an internal buffer. Each
+ * block is prefixed with a buffer offset and a payload length.
+ *
+ * No checksums are included.
+ */
+static int send_rf2500_data(struct fet_proto *dev,
+			    const uint8_t *data, int len)
+{
+	int offset = 0;
+
+	while (len) {
+		uint8_t pbuf[63];
+		int plen = len > 59 ? 59 : len;
+
+		pbuf[0] = 0x83;
+		pbuf[1] = offset & 0xff;
+		pbuf[2] = offset >> 8;
+		pbuf[3] = plen;
+		memcpy(pbuf + 4, data, plen);
+		if (dev->transport->ops->send(dev->transport,
+			pbuf, plen + 4) < 0)
+			return -1;
+
+		data += plen;
+		len -= plen;
+		offset += plen;
+	}
+
+	return 0;
+}
+
+#define PTYPE_ACK		0
+#define PTYPE_CMD		1
+#define PTYPE_PARAM		2
+#define PTYPE_DATA		3
+#define PTYPE_MIXED		4
+#define PTYPE_NAK		5
+#define PTYPE_FLASH_ACK		6
+
+static int parse_packet(struct fet_proto *dev, int plen)
+{
+	uint16_t c = calc_checksum(dev->fet_buf + 2, plen - 2);
+	uint16_t r = LE_WORD(dev->fet_buf, plen);
+	int i = 2;
+	int type;
+	int error;
+
+	if (c != r) {
+		printc_err("fet: checksum error (calc %04x,"
+			" recv %04x)\n", c, r);
+		return -1;
+	}
+
+	if (plen < 6)
+		goto too_short;
+
+	dev->command_code = dev->fet_buf[i++];
+	type = dev->fet_buf[i++];
+	dev->state = dev->fet_buf[i++];
+	error = dev->fet_buf[i++];
+
+	if (error) {
+		printc_err("fet: FET returned error code %d (%s)\n",
+			error, fet_error(error));
+		return -1;
+	}
+
+	if (type == PTYPE_NAK) {
+		printc_err("fet: FET returned NAK\n");
+		return -1;
+	}
+
+	/* Parse packet parameters */
+	if (type == PTYPE_PARAM || type == PTYPE_MIXED) {
+		int j;
+
+		if (i + 2 > plen)
+			goto too_short;
+
+		dev->argc = LE_WORD(dev->fet_buf, i);
+		i += 2;
+
+		if (dev->argc >= FET_PROTO_MAX_PARAMS) {
+			printc_err("fet: too many params: %d\n", dev->argc);
+			return -1;
+		}
+
+		for (j = 0; j < dev->argc; j++) {
+			if (i + 4 > plen)
+				goto too_short;
+			dev->argv[j] = LE_LONG(dev->fet_buf, i);
+			i += 4;
+		}
+	} else {
+		dev->argc = 0;
+	}
+
+	/* Extract a pointer to the data */
+	if (type == PTYPE_DATA || type == PTYPE_MIXED) {
+		if (i + 4 > plen)
+			goto too_short;
+
+		dev->datalen = LE_LONG(dev->fet_buf, i);
+		i += 4;
+
+		if (i + dev->datalen > plen)
+			goto too_short;
+
+		dev->data = dev->fet_buf + i;
+	} else {
+		dev->data = NULL;
+		dev->datalen = 0;
+	}
+
+	return 0;
+
+too_short:
+	printc_err("fet: too short (%d bytes)\n",
+		plen);
+	return -1;
+}
+
+/* Receive a packet from the FET. The usual format is:
+ *     <length (2 bytes)> <data> <checksum>
+ *
+ * The length is that of the data + checksum. Olimex JTAG adapters follow
+ * all packets with a trailing 0x7e byte, which must be discarded.
+ */
+static int recv_packet(struct fet_proto *dev)
+{
+	int pkt_extra = (dev->proto_flags & FET_PROTO_EXTRA_RECV) ? 3 : 2;
+	int plen = LE_WORD(dev->fet_buf, 0);
+
+	/* If there's a packet still here from last time, get rid of it */
+	if (dev->fet_len >= plen + pkt_extra) {
+		memmove(dev->fet_buf, dev->fet_buf + plen + pkt_extra,
+			dev->fet_len - plen - pkt_extra);
+		dev->fet_len -= plen + pkt_extra;
+	}
+
+	/* Keep adding data to the buffer until we have a complete packet */
+	for (;;) {
+		int len;
+
+		plen = LE_WORD(dev->fet_buf, 0);
+		if (dev->fet_len >= plen + pkt_extra)
+			return parse_packet(dev, plen);
+
+		len = dev->transport->ops->recv(dev->transport,
+						dev->fet_buf + dev->fet_len,
+						sizeof(dev->fet_buf) -
+						dev->fet_len);
+		if (len < 0)
+			return -1;
+		dev->fet_len += len;
+	}
+
+	return -1;
+}
+
+static int send_command(struct fet_proto *dev, int command_code,
+		        const uint32_t *params, int nparams,
+			const uint8_t *extra, int exlen)
+{
+	uint8_t datapkt[FET_PROTO_MAX_BLOCK * 2];
+	int len = 0;
+
+	uint8_t buf[FET_PROTO_MAX_BLOCK * 3];
+	uint16_t cksum;
+	int i = 0;
+	int j;
+
+	assert (len + exlen + 2 <= sizeof(datapkt));
+
+	/* Command code and packet type */
+	datapkt[len++] = command_code;
+	datapkt[len++] = ((nparams > 0) ? 1 : 0) + ((exlen > 0) ? 2 : 0) + 1;
+
+	/* Optional parameters */
+	if (nparams > 0) {
+		datapkt[len++] = nparams & 0xff;
+		datapkt[len++] = nparams >> 8;
+
+		for (j = 0; j < nparams; j++) {
+			uint32_t p = params[j];
+
+			datapkt[len++] = p & 0xff;
+			p >>= 8;
+			datapkt[len++] = p & 0xff;
+			p >>= 8;
+			datapkt[len++] = p & 0xff;
+			p >>= 8;
+			datapkt[len++] = p & 0xff;
+		}
+	}
+
+	/* Extra data */
+	if (extra) {
+		int x = exlen;
+
+		datapkt[len++] = x & 0xff;
+		x >>= 8;
+		datapkt[len++] = x & 0xff;
+		x >>= 8;
+		datapkt[len++] = x & 0xff;
+		x >>= 8;
+		datapkt[len++] = x & 0xff;
+
+		memcpy(datapkt + len, extra, exlen);
+		len += exlen;
+	}
+
+	/* Checksum */
+	cksum = calc_checksum(datapkt, len);
+	datapkt[len++] = cksum & 0xff;
+	datapkt[len++] = cksum >> 8;
+
+	/* Copy into buf, escaping special characters and adding
+	 * delimeters.
+	 */
+	if (!(dev->proto_flags & FET_PROTO_NOLEAD_SEND))
+		buf[i++] = 0x7e;
+
+	for (j = 0; j < len; j++) {
+		char c = datapkt[j];
+
+		if (c == 0x7e || c == 0x7d) {
+			buf[i++] = 0x7d;
+			c ^= 0x20;
+		}
+
+		buf[i++] = c;
+	}
+	buf[i++] = 0x7e;
+
+	assert (i < sizeof(buf));
+
+	return dev->transport->ops->send(dev->transport, buf, i);
+}
+
+void fet_proto_init(struct fet_proto *dev, transport_t transport,
+		    int proto_flags)
+{
+	dev->transport = transport;
+	dev->proto_flags = proto_flags;
+	dev->fet_len = 0;
+}
+
+int fet_proto_xfer(struct fet_proto *dev,
+		   int command_code, const uint8_t *data, int datalen,
+		   int nparams, ...)
+{
+	uint32_t params[FET_PROTO_MAX_PARAMS];
+	int i;
+	va_list ap;
+
+	assert (nparams <= FET_PROTO_MAX_PARAMS);
+
+	va_start(ap, nparams);
+	for (i = 0; i < nparams; i++)
+		params[i] = va_arg(ap, uint32_t);
+	va_end(ap);
+
+	if (data && (dev->proto_flags & FET_PROTO_SEPARATE_DATA)) {
+		assert (nparams + 1 <= FET_PROTO_MAX_PARAMS);
+		params[nparams++] = datalen;
+
+		if (send_rf2500_data(dev, data, datalen) < 0)
+			return -1;
+		if (send_command(dev, command_code, params, nparams,
+				 NULL, 0) < 0)
+			return -1;
+	} else if (send_command(dev, command_code, params, nparams,
+				data, datalen) < 0)
+		return -1;
+
+	if (recv_packet(dev) < 0)
+		return -1;
+
+	if (dev->command_code != command_code) {
+		printc_err("fet: reply type mismatch\n");
+		return -1;
+	}
+
+	return 0;
+}
diff --git a/drivers/fet_proto.h b/drivers/fet_proto.h
new file mode 100644
index 0000000..d04b40d
--- /dev/null
+++ b/drivers/fet_proto.h
@@ -0,0 +1,67 @@
+/* MSPDebug - debugging tool for the eZ430
+ * Copyright (C) 2009-2012 Daniel Beer
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#ifndef FET_PROTO_H_
+#define FET_PROTO_H_
+
+#include <stdint.h>
+
+#include "transport.h"
+
+/* Send data in separate packets, as in the RF2500 */
+#define FET_PROTO_SEPARATE_DATA		0x01
+
+/* Received packets have an extra trailing byte */
+#define FET_PROTO_EXTRA_RECV		0x02
+
+/* Command packets have no leading \x7e */
+#define FET_PROTO_NOLEAD_SEND		0x04
+
+/* Data transfer limits */
+#define FET_PROTO_MAX_PARAMS		16
+#define FET_PROTO_MAX_BLOCK		4096
+
+/* Protocol parser structure */
+struct fet_proto {
+	transport_t			transport;
+	int				proto_flags;
+
+	/* Raw packet buffer */
+	uint8_t                         fet_buf[65538];
+	int                             fet_len;
+
+	/* Received packet is parsed into these fields */
+	int				command_code;
+	int				state;
+
+	int				argc;
+	uint32_t			argv[FET_PROTO_MAX_PARAMS];
+
+	uint8_t				*data;
+	int				datalen;
+};
+
+/* Initialize a FET protocol parser */
+void fet_proto_init(struct fet_proto *p, transport_t trans, int proto_flags);
+
+/* Perform a command-response transfer */
+int fet_proto_xfer(struct fet_proto *p,
+		   int command_code, const uint8_t *data, int datalen,
+		   int nparams, ...);
+
+#endif